Orthodontics: Current Principles and Techniques 3rd Edition

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CHAPTER

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Bonding in Orthodontics Björn U. Zachrisson, Tamer Büyükyilmaz

rthodontists now are approaching 35 years of successful, reliable orthodontic bonding in offices around the world. The median bond failure rate for practitioners in the United States is presently around 5%. The only teeth that were banded routinely by a majority of U.S. orthodontists in a recent survey were the maxillary first molars, and all molars and premolars were banded less routinely than in the past.128 The prevailing concepts are challenged continuously by new developments and technical improvements. Achieving a low bond failure rate should be a highpriority objective, for replacing loose brackets is inefficient, time-consuming, and costly. Consequesntly, a continuous search is on for higher bond strengths, better adhesives, simpler procedures, and materials that will bond in the presence of saliva. However, most bond failures result from inconsistencies in the bonding technique and not because of the bonding resins, inadequate bond strengths, or quality of the brackets being used.215 Newer resin systems and alternative methods to bond to enamel may be giving the false impression that one need not be so careful with the bonding procedures as before. The basis for the adhesion of brackets to enamel has been enamel etching with phosphoric acid, as first proposed by Buonocore43 in 1955. In the early 1970s a considerable number of preliminary reports were published on different commercially available direct and indirect bonding systems.198 The first detailed posttreatment evaluation of direct bonding over a full period of orthodontic treatment in a large sample of patients, was published in 1977.251 Since then, product development in terms of adhesive resins, brackets, and technical details has occurred at a rapid rate (Figure 14-1). In fact, the progress has made it difficult for the practicing orthodontist to stay properly oriented. The purpose of this chapter is to update the current available information on bonding to natural and artificial teeth. Further developments are likely to produce significant changes in several of the ideas, clinical suggestions, and even principles presented. Therefore the main emphasis in this chapter is on clinical aspects. Attempts are made to analyze important factors and

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offer advice (based on the authors’ own clinical and research experience and the results published by others) to help make the bonding of attachments and retainers efficient and trouble free. To help organize the contents, the chapter is divided into four parts: 1. Bracket bonding 2. Debonding 3. Bonded retainers 4. Other applications of bonding

BRACKET BONDING The simplicity of bonding can be misleading. The technique undoubtedly can be misused, not only by an inexperienced clinician but also by more experienced orthodontists who do not perform procedures with care. Success in bonding requires understanding of and adherence to accepted orthodontic and preventive dentistry principles. The advantages and disadvantages of bonding versus banding of different teeth must be weighed according to each practitioner’s preferences, skill, and experience. Bonding should be considered as only part of a modern preventive package that also includes a strict oral hygiene program,248 fluoride supplementation,44,185,249 and the use of simple yet effective appliances (Figure 14-1). In other words, complicated mechanics with abundant use of coil springs and multilooped arches lends itself less well to bonding and easily can compromise the integrity of tooth enamel and gingival tissues around brackets on small bonding bases.

Bonding Procedure The steps involved in direct and indirect bracket bonding on facial or lingual surfaces are as follows: • Cleaning • Enamel conditioning • Sealing • Bonding 579

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Figure 14-1 Esthetic comparison between bonded appliances. A, Stainless steel brackets. B, Ceramic brackets. C, Ceramic and gold-coated brackets. D, Lingual bonding.

Cleaning Cleaning of the teeth with pumice removes plaque and the organic pellicle that normally covers all teeth.1 One must exercise care to avoid traumatizing the gingival margin and initiating bleeding on teeth that are not fully erupted. The need for conventional pumice polishing before acid etching has been questioned.139,214However, pumice prophylaxis does not appear to affect the bonding procedure adversely, and cleaning the tooth may be advisable to remove plaque and debris that otherwise might remain trapped at the enamel-resin interface after bonding. Furthermore, Reisner et al.180 found more consistent results when buccal tooth surfaces were abraded lightly with a tungsten carbide bur (#1172) at slow speed (25,000 rpm) than when the surfaces were pumiced for 10 seconds before acid etching.

Enamel conditioning Moisture Control. After the rinse, salivary control and maintenance of a dry working field is essential. Many devices on the market accomplish this: • Lip expanders and cheek retractors • Saliva ejectors • Tongue guards with bite blocks

Figure 14-2 Large Dri-Angle for restriction of saliva from the parotid duct.

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Chapter 14 • Bonding in Orthodontics • • • •

Salivary duct obstructors (Figures 14-2 and 14-3) Gadgets that combine several of these (Figure 14-4) Cotton or gauze rolls Antisialagogues These products are being improved continually, and the clinician must decide which ones work best. For simultaneous molar-to-molar bonding in both arches, a technique using lip expanders, Dri-Angles (to restrict the flow of saliva from the parotid duct), and saliva ejectors (see Figure 14-4) works well.

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Regarding antisialagogues, tablets55 and injectable solutions37,239 of different preparations (e.g., methantheline bromide [Banthine], propantheline bromide [ProBanthine], and atropine sulfate) are available. However, the excellent and rapid saliva flow restriction obtainable with propantheline bromide injections239 is no longer advised. The Council on Dental Therapeutics of the American Dental Association has recommended that this drug not be injected in patients who can take the oral form.

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Figure 14-3 Working field at bonding of second molars.

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Figure 14-4 A, Combined saliva ejector, tongue holder, and bite block (BB-SE) for moisture control during bracket bonding. B, High-speed saliva evacuator with large opening is important for optimal collection of the etchant-water rinse.

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Present experience indicates that antisialagogues generally are not needed for most patients. When indicated, methantheline (Banthine) tablets (50 mg per 100 lb [45 kg] body weight) in a sugar-free drink, 15 minutes before bonding, may provide adequate results.55 Enamel Pretreatment. After the operative field has been isolated, the conditioning solution or gel is applied over the enamel surface for 15 to 30 seconds (see the following discussion). When etching solutions are used, the surface must be kept moist by repeated applications. At the end of the etching period the etchant is rinsed off the teeth with abundant water spray. A high-speed evacuator (see Figure 14-4) is strongly recommended for increased efficiency in collecting the etchant-water

rinse and to reduce moisture contamination on teeth and Dri-Angles. Salivary contamination of the etched surface must not be allowed. (If contamination occurs, rinse with the water spray or re-etch for a few seconds; the patient must not rinse.) Next, the teeth are dried thoroughly with a moistureand-oil-free air source to obtain the well-known dull, frosty appearance (Figure 14-5). Teeth that do not appear dull and frosty white should be re-etched. Cervical enamel, because of its different morphology, usually looks somewhat different from the center and incisal portions of a sufficiently etched tooth10 (see Figures 14-5 and 14-34). The cervical enamel should not be re-etched in attempts to produce a uniform appearance over the entire enamel surface.

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Acid-etch conditioning of enamel before bracket bonding. A, Frosty white appearance. B and C, Scanning electron micrograph of an enamel surface that has been etched with 37% phosphoric acid. (In B the prism centers have been removed preferentially, whereas in C the loss of prism peripheries demonstrates the headand-tail arrangement of the prisms.) D to F, Transverse section of an etched porous enamel surface showing two distinct zones, the qualitative porous zone (QPZ) and the quantitative porous zone. In the latter an even row of resin tags (T) may penetrate.

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Chapter 14 • Bonding in Orthodontics This procedure probably reflects the general use of acid etching in orthodontics. However, considerable discussion of and continuous debate over several aspects of enamel pretreatment remain: 1. Should the etch cover the entire facial enamel or only a small portion outside the bracket pad? 2. Are gels preferable to solutions? 3. What is the optimal etching time? Is it different for young and old teeth? 4. Is sandblasting as effective as acid etching? 5. What is the preferred procedure for deciduous teeth? 6. Is prolonged etching necessary when teeth are pretreated with fluoride? 7. Will incorporation of fluorides in the etching solution increase the resistance of enamel to caries attack? 8. Is etching permissible on teeth with internal white spots? Or is it more likely that the etchant will open up underlying demineralized areas? 9. How much enamel is removed by etching, and how deep are the histologic alterations? Are they reversible? Is etching harmful? 10. Should means other than acid etching with phosphoric acid (e.g., polyacrylic acid, maleic acid, or self-etching primers) be preferred? Although these questions are of considerable theoretical interest, most debate concerning acid etching appears to be of limited clinical significance, at least as it bears on bond strength. In other words, good bond strength apparently depends much more on (1) avoiding moisture contamination and (2) achieving undisturbed setting of the bonding adhesive than on variations in the etching procedures. Some short answers to the foregoing questions are as follows: 1. Although it may seem logical to etch an area only slightly larger than the pad, clinical experience over more than 25 years indicates that etching the entire facial enamel with solution is harmless—at least when a fluoride mouth rinse is used regularly. 2. No apparent difference exists in the degree of surface irregularity after etching with an acid solution compared with etching with an acid gel.38 Gels provide better control for restricting the etched area but may require more thorough rinsing afterward. The most popular enamel/dentin etchant in general dentistry is the Ultraetch 35% phosphoric acid blue gel (Ultradent Products, South Jordan, Utah). This gel is dispensed by syringe; has adequate color contrast, smooth consistency, and almost ideal viscosity for application and rinsing off cleanly; and provides an even, nicely demarcated white frosted appearance. This etchant is recommended whenever extra good etching of enamel is desired, such as for deciduous

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teeth, for rebonding brackets, and for bonded retainers (see Figure 14-60, A). Studies38,39,154, 158,235 and clinical experience indicate that 15 to 30 seconds is probably adequate for etching most young permanent teeth. However, important individual variation exists in enamel solubility between patients, between teeth, and within the same tooth. One benefit of conventional acid etching is that it tends to neutralize the differences between individuals and between teeth. Thus a phosphoric acid etch of sufficient time can compensate for those individuals whose enamel is more acid resistant. Attempts to use materials that produce a minimal etch—such as glass ionomers, hybrid resin glass ionomers, and the newer self-etching primers—appear to result in increased clinical bond failure rates. Sandblasting without acid etching produces lower bond strengths than acid etching and consistently results in bond failures at the enamel-adhesive interface.168,180 Sandblasting followed by acid etching produces bond strengths comparable to or higher than acid-etched enamel.180 A recommended procedure for conditioning deciduous teeth is to sandblast with 50-µm aluminum oxide for 3 seconds to remove some outermost aprismatic enamel and then etch for 30 seconds with the Ultraetch 35% phosphoric acid gel. The failure rate with this procedure for the authors is less than 5%. Clinical and laboratory experience38,39 indicates that extra etching time is not necessary when teeth have been pretreated with fluoride. When in doubt, check that the enamel looks uniformly dull and frosty white after the etch; if it does, surface retention is adequate for bonding. Fluoridated phosphoric acid solutions and gels provide an overall morphologic etching effect similar to nonfluoridated ones and give adequate bond strength in direct-bonding procedures.46,91,149 Further studies are needed to determine their effectiveness regarding caries protection around brackets over a full period of orthodontic treatment. One should exercise caution when etching over acquired and developmental demineralizations. The procedure is best avoided. If this is impossible, a short etching time, the application of sealant or primer, and the use of direct bonding with extra attention to not having areas of adhesive deficiency are important. The presence of voids, together with poor hygiene, can lead to metal corrosion142 and indelible staining of underlying developmental white spots.58 A routine etching removes from 3 to 10 µm of surface enamel.58,176,200,221 Another 25 µm reveals subtle histologic alterations,45,102,199 creating the

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Figure 14-6 Fitting surface of adhesive resin after the removal of enamel by demineralization. This surface shows an evenly distributed row of tags. (Courtesy ML Swartz, Encino, California.)

necessary mechanical interlocks (Figure 14-6; see also Figure 14-5). Deeper localized dissolutions generally cause penetration to a depth of about 100 µm or more.45,73,199 Although laboratory studies indicate that the enamel alterations are largely (though not completely) reversible,197,199 the overall effect of applying etchant to healthy enamel is not detrimental. This point is augmented by the fact that normally enamel is from 1000 to 2000 µm thick73,267(except as it tapers toward the cervical margin), abrasive wear of facial enamel is normal and proceeds at a rate of up to 2 µm per year, and facial surfaces are self-cleaning and not prone to caries.143 10. Use of polyacrylic acid with residual sulfate is reported142 to provide retention areas in enamel similar to those after phosphoric acid etching with less risk of enamel damage at debonding. However, other researchers have found much weaker bonds.14,32,79,177 The same is true for the use of maleic acid.174

Sealant, primers After the teeth are completely dry and frosty white, a thin layer of bonding agent (sealant, primer) may be painted over the etched enamel surface. The coating may be thinned by a gentle air burst for 1 to 2 seconds. Bracket placement should be started immediately after all etched surfaces are coated. Much confusion and uncertainty surround the use of sealants and primers in orthodontic bonding. Research has been devoted to determining the exact function of the intermediate resin in the acid-etch procedure. The findings are divergent. Some investigators conclude that

an intermediate resin is necessary to achieve proper bond strength; some indicate that intermediate resin is necessary to improve resistance to microleakage; others feel intermediate resin is necessary for both reasons; still others do not think that the intermediate resin is necessary at all.118,175,236 A particular problem in orthodontics is that the sealant film on a facial tooth surface is so thin that oxygen inhibition of polymerization is likely to occur with autopolymerizing sealants. With acetone-containing and light-polymerized sealants, nonpolymerization seems less of a problem. Why then should a sealant be of any value in bracket bonding? If nothing else, sealant permits a relaxation of moisture control because this is no longer critical after resin coating. Sealants also provide enamel cover in areas of adhesive voids, which is probably especially valuable with indirect bonding. The caries protection of sealant around the bracket base is more uncertain,58,103,236 and further studies are needed on the clinical merits of fluoride-containing sealants.25,59 Ceen and Gwinnett59 found that light-polymerized sealants protect enamel adjacent to brackets from dissolutions and subsurface lesions, whereas chemical-curing sealants may polymerize poorly, exhibit drift, and have low resistance to abrasion.58,266 Moisture-insensitive Primers. In an attempt to reduce the bond failure rates under moisture contaminations, hydrophilic primers that can bond in wet fields (Transbond MIP, 3M/Unitek, Monrovia, California; and Assure, Reliance Orthodontics, Itasca, Illinois) have been introduced as a potential solution. Laboratory studies investigating the effect of saliva contamination on bond strength show conflicting results.100,110,191,195,272 Although bond strengths were significantly lower under wet conditions than in dry conditions, the hydrophilic primers may be suitable in difficult moisture-control situations. This may be the case in some instances of second molar bonding and when there is risk for blood contamination on half erupted teeth and on impacted canines. For optimal results, the moisture-insensitive primers should be used with their respective adhesive resins. The hydrophilic resin sealants or primers polymerize in the presence of a slight amount of water, but they will not compensate routinely for saliva contamination. When bonding to enamel, one must place the resin sealant or resin primer onto the prepared enamel before the pellicle (biofilm) from the saliva. This is not particularly difficult but is crucial to a successful enamel bond.215 Self-Etching Primers. Combining conditioning and priming into one step may result in improvement in time and cost-effectiveness for clinicians and patients, provided the clinical bond failure rates are not increased significantly. The main feature of the singlestep etch/primer bonding systems is that no separate

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Chapter 14 • Bonding in Orthodontics acid etching of the enamel and subsequent rinsing with water and air spray is required; the liquid itself has a component that conditions the enamel surface. The active ingredient of the self-etching primers (SEPs) is a methacrylated phosphoric acid ester that dissolves calcium from hydroxyapatite. Rather than being rinsed away, the removed calcium forms a complex and is incorporated into the network when the primer polymerizes. Etching and monomer penetration to the exposed enamel rods are simultaneous, and the depth of etch and primer penetration are identical. Three mechanisms act to stop the etching process. First, the acid groups attached to the monomer are neutralized by forming a complex with calcium from hydroxyapatite. Second, as the solvent is driven from the primer during the airburst step, the viscosity rises, slowing the transport of acid groups to the enamel interface. Finally, as the primer is light cured and the primer monomers are polymerized, transport of acid groups to the interface is stopped.62 Scanning electron microscopy examination of the impression of SEP-treated enamel shows different surface characteristics from acid-etched enamel (Figure 14-7, B and C). Instead of the wellknown distinct honeycombed structure with microtag and macrotag formation (Figure 14-7, A), one finds an irregular but smooth hybrid layer, 3 to 4 µm thick and irregular tag formation with no apparent indentations of enamel prism or core material. The minimal etch obtained with the SEPs indicates that the majority of

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the bond may be more of a chemical bond with the calcium in the enamel than the mechanical bond achieved with a conventional phosphoric acid etch.215 Clinical procedure: For optimal bonding with the SEP Transbond Plus (3M/Unitek), the authors recommend the following sequence (Figure 14-8): 1. Dry the tooth surface. 2. Apply Transbond Plus. The single-use package consists of three compartments. The first compartment contains methacrylated phosphoric acid esters, photosensitizers, and stabilizers. The second compartment contains water and soluble fluoride. The third compartment contains an applicator microbrush (Figure 14-8, A and B). Squeezing and folding the first compartment over to the second activates the system. The mixed component then is ejected to the third to wet the applicator tip. Stay on the tooth surface to avoid gingival irritation. Rub thoroughly for at least 3 seconds and always wet the surface with new solution to ensure the monomer penetration (Figure 14-8, C and D). The presence of water in the chemical composition of Transbond Plus may necessitate air drying, but as the operator moves from one side to the other, the solvent evaporates and drying is no longer necessary. 3. Bond the bracket with Transbond XT (3M/Unitek) and cure with light.

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Comparison of scanning electron microscopy views of adhesive under the bracket base after phosphoric acid etching and use of self-etching primer (Transbond Plus). A, Adhesive under the bracket base after removal of phosphoric acid-etched enamel. Note exact replica of honeycomb appearance (×1500). B, Cross section showing Transbond Plus–treated enamel and outer surface of Transbond Plus layer on enamel (×2000). C, Adhesive under the bracket base after complete removal of the Transbond Plus–treated enamel (×1500).

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Figure 14-8 Application of self-etching primer (Transbond Plus) on enamel surface of maxillary incisor (see text for explanation).

The use of the new SEPs for orthodontic purposes has not yet been evaluated fully. Recent laboratory studies35 indicate that the shear bond strength of mix (Transbond Plus) and no-mix (Ideal 1, GAC International, Bohemia, New York) SEPs were not significantly different from one another. In the authors’ in vitro study,48 the shear bond strengths of the acidic primer Transbond Plus was significantly higher than that obtained with conventional 37% phosphoric acid etching. Clinical bond strengths using SEPs are not yet reported in a large sample for a full period of orthodontic treatment. In a 6-month clinical test period, Ireland et al.115 found that bond failures with an SEP were higher than those with conventional etching and priming. The author’s experience since June 2001 (Büyükyilmaz, unpublished findings) with more than 2300 brackets and tubes on 106 patients indicates a reasonably low failure rate (4.1%), which still is significantly higher than the authors’ failure rates for conventional phosphoric acid etching. Debonding brackets after SEP application also is easier and requires shorter time to remove the adhesive compared with acid etching. When deciding which etching and priming system to use, each clinician must weigh bond failure rates against the time saved in bonding and debonding.

Figure 14-9 Instruments used for bracket bonding with self-etching primer (Transbond Plus) and light-initiated adhesive resin (Transbond XT).

Bonding Immediately after all teeth to be bonded have been painted with sealant or primer, the operator should proceed with the actual bonding of the attachments (Figure 14-9). At present, the majority of clinicians

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Chapter 14 • Bonding in Orthodontics routinely bond brackets with the direct rather than the indirect technique.128 In a 2002 survey in the United States, more than 90% of orthodontists routinely were using direct bonding. Indirect bonding was used routinely by about 10%. Remarkably, now about 75% of the U.S. specialists have replaced the chemically cured one- or two-paste adhesives and have adopted the light-initiated bonding resins.128 Many different adhesives exist for direct bonding, and new ones appear continuously. However, the basic bonding technique is only slightly modified for varying materials according to each manufacturer’s instructions. The easiest method of bonding is to have a slight excess of adhesive to the backing of the attachment (Figure 14-10) and then place the attachment on the tooth surface in its correct position. When bonding attachments one at a time with new adhesive, the operator can work in a relaxed manner and obtain optimal bond strength for each bracket. Hurrying is not necessary because plenty of time is available for placing the bracket in its correct position, checking it, and if necessary repositioning it within the working time of the adhesive or before light curing. The recommended bracket bonding procedure251,263 (with any adhesive) consists of the following steps: 1. Transfer 2. Positioning

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3. Fitting 4. Removal of excess Transfer. The clinician grips the bracket with reverse action tweezers and then applies the mixed adhesive to the back of the bonding base. The clinician immediately places the bracket on the tooth close to its correct position (Figure 14-11). Positioning. The clinician uses a placement scaler to position the brackets mesiodistally and incisogingivally and to angulate them accurately relative to the long axis of the teeth (Figure 14-11, A). Proper vertical positioning may be enhanced by different measuring devices or height guides. A mouth mirror will aid in horizontal positioning, particularly on rotated premolars (Figure 14-12). Fitting. Next, the clinician turns the scaler and with one-point contact with the bracket, pushes firmly toward the tooth surface.121 The tight fit will result in good bond strength, little material to remove on debonding, optimal adhesive penetration into bracket backing, and reduced slide when excess material extrudes peripherally. The clinician should remove the scaler after the bracket is in the correct position and should make no attempts to hold the bracket in place with the instrument. Even slight movement may disturb the setting of the adhesive. Totally undisturbed setting is essential for achieving adequate bond strength.263

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Figure 14-10 Placement of chemically curing (A) and light-curing (B to D) adhesive resin on contact surface of bracket.

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Figure 14-11 Direct bracket bonding with light-cured adhesive resin. A, After the bracket is transferred to the tooth surface, orientation (angulation, height, mesiodistal position) is made with placement scaler. B, Next, the scaler is used to seat the bracket firmly toward the tooth surface. Excess adhesive is removed with the scaler along the pad periphery. C, Light curing.

Figure 14-12 Bracket position on difficult teeth may be checked with a mouth mirror.

Removal of Excess. A slight bit of excess adhesive is essential to minimize the possibility of voids and to be certain that the adhesive will be buttered into the bracket backing when the bracket is being fitted. The excess is particularly helpful on teeth with abnormal morphology. Excess adhesive will not be worn away by toothbrushing and other mechanical forces (Figure 14-13); it must be removed (especially along the gingival margin) with the scaler before the adhesive has set (see Figure 14-11, B) or with burs after setting (Figure 14-14). Most important is to remove the excess adhesive to prevent or minimize gingival irritation and plaque

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buildup around the periphery of the bonding base (Figures 14-15 and 14-16). Removal of excess adhesive reduces periodontal damage and the possibility of decalcification. Clinically significant gingival hyperplasia and inflammation rapidly occur when excess adhesive comes close to the gingiva and is not removed properly.251,263 In addition, removal of excess adhesive can improve esthetics not only by providing a neater and cleaner appearance but also by eliminating exposed adhesive that might become discolored in the oral environment. When the procedure just described has been repeated for every bracket to be bonded, the clinician carefully checks the position of each bracket (see Figure 14-12). Any attachment that is not in good position should be removed with pliers and rebonded immediately. After inserting a leveling arch wire, the clinician instructs the patient how to brush properly around the brackets and arch wires and gives a program of daily fluoride mouth rinses (0.05% NaF) to follow.249 Bonding to Premolars. The most difficult technical problem for bonding to maxillary first and second premolars is to obtain accurate bracket placement. The visibility for direct bonding is facilitated if these teeth are bonded without a lip expander, one side at a time. Bracket positions should be controlled using a small mouth mirror. For newly erupted mandibular premolars, gingivally offset brackets are recommended. The gingival third of these teeth may have a high incidence of aprismatic enamel and an enamel rod direction that is less retentive of resin tags.213

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Figure 14-13 Typical wear pattern of excess adhesive (EA). Scanning electron micrographs of a replica model (A), at the time of bonding (B and D), and 6 months later (C and E). An example of abrasive wear of adhesive with large filler particles is shown in B and C and of adhesive with submicrometer-sized fillers in D and E. Br, Bracket; BP, bracket pad; BS, bracket slot; BW, bracket wing; ES, enamel surface.

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Bonding to Molars. With the difficulty of banding in young patients, particularly second molars, bonding these and other molars is advantageous. With special technique and care (see Figure 14-3), the routine bonding of first, second, and third molars can be accomplished with high success rates.

A and B, Use of a large (#7006) and a small oval tungsten carbide bur for removal of set adhesive around the bracket base and along the gingival margin, respectively. C, Small burs are also useful under ceramic bracket tie-wings.

Recently introduced resin-modified glass ionomer cements (chemical and light cured) claim to be able to bond to saliva-contaminated enamel surfaces without phosphoric acid etching.197 This is an attractive feature, but these cements have a disadvantage when bonding molar attachments. The liquid contains polyacrylic and

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Figure 14-16 Irrespective of the bonding technique, poor oral hygiene invariably results in significant hyperplastic gingival changes. This has occurred even though excess adhesive was removed carefully.

Types of Adhesives Figure 14-15 Relationship between excess adhesive (EA) and gingival inflammation. Note the hyperplastic gingival changes on the distal aspect (open arrow), where excess adhesive is close to the gingival margin. Less reaction occurs on the mesial aspects, where adhesive is farther from the gingiva.

maleic acids, which will remove contaminants and change the enamel surface mechanically but will not create micromechanical retention as well as 37% phosphoric acid does. The bond strength with resin-modified glass ionomer cements is significantly lower than that of composite resins after phosphoric acid etching.77,133,244 For optimal bond strength, it appears preferable to establish adequate moisture control and bond molar attachments with conventional bisphenol A diglycidyl dimethacrylate (bis-GMA) composite resins. The following procedure is recommended for direct bonding of molars: 1. The first and second molars (and third, if applicable) are bonded separately from the other teeth to permit concentration on access, visibility, and moisture control. 2. A dry field is obtained by a Dri-Angle in the buccal side and a cotton roll. The saliva ejector is positioned on the side to be bonded, adjacent to the second molar. The scaler or a cotton roll is placed over the Dri-Angle for tissue retraction (see Figure 14-3). 3. The bonding procedures are performed on one side at a time.

Two basic types of dental resins may be used for orthodontic bracket bonding. Both are polymers and are classified as acrylic or diacrylate resins. Both types of adhesive exist in filled or unfilled forms. The acrylic resins (e.g., Orthomite [Sun Medical, Tokyo, Japan] and Genie [Lee Pharmaceuticals, South EI Monte, California]) are based on self-curing acrylics and consist of methylmethacrylate monomer and ultrafine powder. Most diacrylate resins are based on the acrylic modified epoxy resin mentioned in the introduction: bis-GMA or Bowen’s resin. A fundamental difference is that resins of the first type form linear polymers only, whereas those of the second type may be polymerized also by crosslinking into a three-dimensional network. This crosslinking contributes to greater strength, lower water absorption, and less polymerization shrinkage.182 A number of independent investigations indicate that the filled diacrylate resins of the bis-GMA type (e.g., Concise [3M, St. Paul, Minnesota] and Phase-II [Reliance Orthodontics]) have the best physical properties and are the strongest adhesives for metal brackets.51,121,263 Acrylic or combination resins have been most successful with plastic brackets. Some composite resins contain large, coarse quartz or silica glass particles of highly variable size averaging 3 to 20 µm41 that impart abrasionresistance properties. Other resins contain minute filler particles of uniform size (0.2 and 0.30 µm) that consequently yield a smoother surface that retains less plaque263 and is more prone to abrasion.41 Reported failure rates for steel mesh–backed brackets direct bonded with highly filled diacrylate resins may be as low as 1% to 4%.263 Buzzitta et al.51 found that a highly filled diacrylate resin with large filler particles gave the highest values of in vitro body strength for metal brackets.

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Chapter 14 • Bonding in Orthodontics Several alternatives exist to chemically autopolymerizing paste-paste systems.

No-mix adhesives No-mix adhesives (e.g., Rely-a-Bond [Reliance Orthodontics] and System 1+ [Ormco Corporation, Glendora, California]) set when one paste under light pressure is brought together with a primer fluid on the etched enamel and bracket backing or when another paste on the tooth is to be bonded. Thus one adhesive component is applied to the bracket base while another is applied to the dried etched tooth. As soon as the bracket is positioned precisely, the orthodontists presses the bracket firmly into place and curing occurs, usually within 30 to 60 seconds. Although the clinical bonding procedure may be simplified with the no-mix adhesives, little long-term information is available on their bond strengths compared with those of the conventionally mixed paste-paste systems. Furthermore, little is known about how much unpolymerized rest monomer remains in the cured adhesive220 and its eventual toxicity. In vitro tests have shown that liquid activators of the no-mix systems are definitely toxic86,220; allergic reactions have been reported in patients, dental assistants, and doctors when such adhesives were used (Figure 14-17).

Light-polymerized adhesives The desire to cure on demand is driving an increasing number of orthodontic practices to use light-cured adhesives instead of the more traditional paste-paste adhesives requiring in-office mixing. The light-initiated resins by now have become the most popular adhesives for a majority of orthodontists128 (see Figures 14-9 and 14-10). These resins offer the advantage of extended, though not indefinite, working time. This in turn provides the opportunity for assistants to place the brackets, with the orthodontist following up with any final positioning.

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Light-cured resins used with metal brackets are usually dual-cure resins incorporating light initiators and a chemical catalyst. Maximum curing depth of light-activated resins depends on the composition of the composite, the light source, and the exposure time.189,224 Bond strength for light-activated materials is reported to be comparable in vitro to those of chemically cured composites,217 but the material may not be as reliable in vivo.72,90,194,215 Light-cured adhesives are particularly useful in situations in which a quick set is required, such as when rebonding one loose bracket or when placing an attachment on an impacted canine after surgical uncovering, with the risk for bleeding. But light-cured adhesives are also advantageous when extra-long working time is desirable. This may be the case when difficult premolar bracket positions need to be checked and rechecked with a mouth mirror before the bracket placement is considered optimal. Fluoride-releasing, visible light–curing adhesives are also available,163,226 but further long-term clinical testing of their bond strength, durability, and caries-preventive effect is necessary. Metallic and ceramic brackets precoated with lightcured composite and stored in suitable containers are practical in use and are becoming increasingly more popular among clinicians.128 Such brackets have consistent quality of adhesive, reduced flash, reduced waste, improved cross-infection control, and adequate bond strength.34 Recently, some precoated brands (APC Plus, 3M/Unitek) are provided with a color change adhesive for easier and more thorough flash cleanup.

Light sources The orthodontist has the following options for light sources: 1. Conventional and fast halogen lights: In light-initiated bonding resins the curing process begins when a

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Figure 14-17 A, Allergic reaction to bonding adhesive. B, Fingertips of a dental assistant.

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photoinitiator is activated. Most photoinitiator systems use camphoroquinone as the absorber,6 with the absorption maximum in the blue region of the visible light spectrum at a wavelength of 470 nm. Until recently, the most common method of delivering blue light has been halogen-based light-curing units (e.g., Ortholux XT, 3M/Unitek). Halogen bulbs produce light when electric energy heats a small tungsten filament to high temperatures. Despite their common use, halogen bulbs have several disadvantages. The light power output is less than 1% of the consumed electric power, and halogen bulbs have a limited lifetime of about 100 hours because of degradation of the components of the bulb by the high heat generated. The halogen lights can cure orthodontic composite resins in 20 seconds and light-cured resin-modified glass ionomers in 40 seconds per bracket.193 This prolonged curing time is inconvenient for the clinician and the patient. Various attempts have been made therefore to enhance the speed of the light-curing process. Fast halogens (e.g., Optilux 501 or Demetron from Kerr, Orange, California) have significantly higher-intensity output than other current halogen lights, and this is accomplished by using higher-output lamps or using turbo tips that focus the light and concentrate it into a smaller area. By this means, curing times can be reduced to half of the time needed with conventional halogen lights. Limitations of filter technique and thermal problems make further improvements of conventional curing lights difficult. 2. Argon lasers: In the late 1980s, argon lasers promised to reduce the curing times dramatically.216,237 Argon lasers produce a highly concentrated beam of light

centered around the 480-nm wavelength. In addition, the light is collimated, which results in more consistent power density over distance. One interesting potential of the argon laser is its ability to protect the lased enamel surface against decalcification. Recent studies have shown that argon laser irradiation significantly reduces enamel demineralization around orthodontic brackets.7,156 Although the curing times could be reduced to 5 seconds for unfilled and 10 seconds for filled resins with argon laser, their use in orthodontics at present is not extensive,128 probably because of their high cost and poor portability. 3. Plasma arc lights: In the mid-1990s, the xenon plasma arc lamp was introduced for high-intensity curing of composite materials in restorative dentistry. This lamp has a tungsten anode and a cathode in a quartz tube filled with xenon gas. When an electric current is passed through xenon, the gas becomes ionized and forms a plasma made up of negatively and positively charged particles and generates an intense white light. Plasma arc lights are contained in base units (Figure 14-18, A) rather than in guns because of the high voltage used and heat generated. The light guide is stiff because of the gel inside. The white light is filtered to blue wavelengths, with a narrow spectrum between 430 and 490 nm. Whereas the conventional halogen lamps emit light with an energy level of 300 mW, the plasma arc lamp has a much higher peak energy level of 900 mW. The advantage of the high-intensity light is that the amount of light energy needed for polymerization of the composite resin can be delivered in a much shorter time. Recent clinical studies194 indicate that exposure times of 3 to 5 seconds for metal brackets and even

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Figure 14-18 Light-curing times can be reduced greatly with plasma arc and light-emitting diode light curing sources. A, PowerPac plasma arc unit. B, Ortholux LED.

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Chapter 14 • Bonding in Orthodontics shorter times for ceramic brackets129 yield similar bond failure rates as for brackets cured with a conventional halogen light for 20 seconds. Therefore plasma arc lights significantly reduce the curing time of orthodontic brackets without affecting the bond failure rate. The heat generated by the high-intensity lights and the possibility of harming the pulp tissue have been addressed in several publications.152,172 In primates, Zach and Cohen247 reported permanent pulp damage when the pulpal temperature rose above 42.5° C. The increase in pulpal temperature in a restorative preparation was only 2.8° C with conventional halogen and 1.1° C with plasma arc light, respectively.16 Thus the use of the plama arc light for curing orthodontic adhesives for 5 to 10 seconds should be safe regarding the pulp temperature.160 4. Light-emitting diodes (LEDs): The most recent light source category is the LED sources (Figure 14-18, B). In 1995 Mills et al.151 proposed solid-state LED technology for polymerization of light-initiated resins to overcome the shortcomings of conventional halogen lights. Light-emitting diodes use junctions of doped semiconductors to generate the light. They have a lifetime of more than 10,000 hours and undergo little degradation of output over this time. Light-emitting diodes require no filters to produce blue light, resist shock and vibration, and take little power to operate. The authors’ in vitro results229 suggest that LED curing of 20 and 40 seconds yielded statistically similar results to curing of 40 seconds by conventional halogen light sources. However, 10 seconds of LED curing (Elipar FreeLight, 3M/ESPE) resulted in significantly reduced shear bond strength values. The longer life span and more consistent light output of LEDs compared with halogen bulb technology show promise for its use in orthodontics. New-generation LEDs with higher-intensity diodes may shorten the curing times further (e.g., the new Ortholux LED by 3M/Unitek [see Figure 14-18, B] has recommended curing times of 10 seconds for metal and 5 seconds for ceramic brackets), but further studies and clinical trials should be performed before validation. In conclusion regarding the use of different light sources and light-initiated adhesives, the authors’ laboratory studies provided the following results: • The light source and adhesive must be compatible. • All new light sources cure resins faster than conventional halogen lights. • Fast halogen sources are more brand specific but generate low heat and are less expensive than plasma lights and LEDs. • Plasma arc lights offer the shortest curing times but are expensive and generate heat.

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• Light-emitting diodes have small size, are cordless, are quiet, generate minimal heat, and perform favorably compared with conventional and fast halogen sources.

Glass ionomer cements The glass ionomer cements were introduced in 1972, primarily as luting agents and direct restorative material, with unique properties for bonding chemically to enamel and dentin and to stainless steel and being able to release fluoride ions for caries protection. The secondgeneration water-hardening cements contain the same acids in freeze-dried form or an alternative powdered copolymer of acrylic and maleic acids. The glass ionomer cements were modified to produce dual-cure or hybrid cements (e.g., Fuji Ortho LC, GC America, Alsip, Illinois). Glass ionomer and light-cured glass ionomer cements now are used routinely by most orthodontists128 for cementing bands because they are stronger than zinc phosphate and polycarboxylate cements, with less demineralization at the end of treatment87,137,150 and adhesion to enamel and metal.114 However, glass ionomer cements are susceptible to moisture contamination during the setting reaction and require up to 24 hours to reach maximum strength.243 The light-activated resinmodified glass ionomers are faster setting and show higher initial and sustained shear bond strengths than the chemically cured ones. The chemical composition and setting reaction among resin ionomer hybrids vary widely. Some hybrids are categorized as modified composites (compomers or polyacid modified composite resins) and others as true resin modified glass ionomer cements. The compomers are essentially resin matrix composites, where the filler is replaced by ion-leachable aluminosilicate glass. No acid-base reaction occurs during setting, but often a light-activated free radical polymerization of the methacrylate groups occurs. In contrast, the resin-modified glass ionomer cements are hybrids of their two parent groups and incorporate an acid-base reaction in the setting process.147,155 Few reports are available about the clinical performance over a substantial time for resin-modified glass ionomer cements for bracket bonding. In 1999 Gaworski et al.92 published the results comparing a glass ionomer (Fuji Ortho LC) with a composite resin (Light Bond, Reliance Orthodontics) for bonding brackets over 12 to 14 months. The failure rates were 24.8% and 7.4%, respectively, with no statistical difference in incidence of decalcification between the two adhesives. When polyacrylic acid was used for conditioning and no saliva contamination occurred, Hitmi et al.108 found a failure rate of 7% for Fuji Ortho LC. Conditioning with polyacrylic acid removes surface contaminants and alters the surface energy by diffusion of the acid and exchange of ions. The pretreatment with polyacrylic acid facilitates a chemical bond between the glass ionomer and

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the enamel and thus should be performed before bracket bonding with glass ionomer. In a double-blind, randomized, controlled clinical trial by Gorton and Featherstone,99 the quantitative microhardness tests of teeth bonded with Fuji Ortho LC showed significantly less mineral loss compared with teeth bonded with light-cured composite resin (Transbond XT). When bond strength is the main criterion for selecting an adhesive, composite resins are recommended. However, the decalcification risk with fixed orthodontic appliances in some patients should not be ignored, and the use of fluoridereleasing cements may have an impact in preventing this phenomenon. Selection of adhesives for direct bonding among the myriad alternatives available depends largely on what handling characteristics are preferred and on the individual office philosophy regarding delegation (Figure 14-19). Bond failures, which are failures at the enamel-adhesive interface (adhesive failures), are likely to result from inadequate technique (e.g., inadequate etch or moisture or

saliva contamination with the pellicle). Failures in the adhesive-bracket interface (cohesive failures) more likely are caused by moving the bracket during the initial polymerization, applying an excessive load to the bracket while the resin is still polymerizing, or simply that too little pressure was used when the adhesive resin was pushed into the mesh base of the bracket. The incidence of cohesive-type bond failures may increase with the adoption of light-initiated bonding adhesives. The polymerization of bonding materials is a chain reaction. The light cannot penetrate entirely under metal brackets. The polymerization only begins at the edges of the bracket base and then continues as a chain reaction. The light-initiated bonding resins under metal brackets may take as long as 3 days to reach maximum polymerization or strength.215 The set under clear brackets, however, is almost instantaneous. An important factor related to cohesive-type bond failures with light-initiated resins is moving the bracket after the resin has begun to set. The operatory light in the

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Figure 14-19 The bond strength of adhesives is satisfactory for bonding lower second molars routinely. A problem may be encountered, however, in arch wire removal. The problem is solved with the following technique: A, A distally bent-over arch wire from a bonded second molar is loosened by a Coon or Steiner tying pliers and a Mathieu needle holder. The needle holder acts as a stop on the arch wire a few millimeters from the mesial end of the buccal tube. B, The Coon pliers rest at the mesial part of the tube and at the stop. By closing the tying pliers, the operator gently releases the arch wire, often without even needing to straighten the arch wire at the distal end of the tube. C, Because the pressure is equal on both ends of the buccal tube, the bond is not stressed unduly.

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Chapter 14 • Bonding in Orthodontics office may be starting the polymerization. For success in bonding with light-activated resins, a recommendation is that the clinician expose the bracket to the curing light immediately after placement or keep the time interval between placement and curing to a minimum.216

Brackets Three types of attachments are presently available for orthodontic bracket bonding: plastic based, ceramic based, and metal (stainless steel, gold-coated, titanium) based. Of these, most clinicians prefer the metal attachments for routine applications, at least in children.128

Plastic brackets Plastic attachments are made of polycarbonate and are used mainly for esthetic reasons. Pure plastic brackets lack strength to resist distortion and breakage, wire slot wear (which leads to loss of tooth control), uptake of water, discoloration, and the need for compatible bonding resins.182 Such plastic brackets may be useful in minimal-force situations and for treatments of short duration, particularly in adults. New types of reinforced plastic brackets with and without steel slots inserts have been introduced. Steel-slotted plastic brackets are useful as an esthetic alternative, but added bulk is required to provide adequate strength of the tie-wings.

Ceramic brackets Ceramic brackets have become an important though sometimes troublesome part of today’s orthodontic practice. Ceramic orthodontic brackets are machined from monocrystalline or polycrystalline aluminum oxide.32,212 Theoretically, such brackets should combine the esthetics of plastic and the reliability of metal brackets.

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In contrast to current elastic ligatures, polycrystalline and single-crystal brackets resist staining and discoloration. Steel ligatures can be used with caution.83,84,212 Ceramic brackets bond to enamel by two different mechanisms: (1) mechanical retention via indentations and undercuts in the base and (2) chemical bonding by means of a silane coupling agent. With mechanical retention the stress of debonding is generally at the adhesivebracket interface, whereas the chemical bonding may produce excessive bond strengths, with the stress at debonding shifted toward the enamel-adhesive interface (see Debonding). Chemically cured and light-cured adhesives are useful for ceramic brackets.53,159,212 Brackets preloaded with light-cured paste can be applied to the teeth and pressed firmly in place in their approximate location. After adjusting the brackets and removing excess adhesive, the operator bonds the brackets in place with the curing light.161 However, the pure ceramic brackets that are available show some significant drawbacks: 1. The frictional resistance between orthodontic wire and ceramic brackets is greater and less predictable than it is with steel brackets.29,95,116,136 This unpredictability makes determining optimal force levels and anchorage control difficult. Ceramic brackets with a steel slot insert (Figure 14-20; see Figure 14-22) to reduce friction32,52,53 are therefore more reliable for clinical purposes. 2. Ceramic brackets are not as durable as steel brackets and are brittle by nature. These brackets may break during orthodontic treatment, particularly when full-size (or close to full-size) stainless steel arch wires are used for torquing purposes.84,112

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A

Figure 14-20 A, Steel-slotted ceramic brackets (Clarity) just bonded in adult patient. Note that canine and right central incisor brackets in this case are angulated to move the root apices of these teeth apart with the purpose of providing adequate space for later single-implant insertion. B, Right lateral incisor is acrylic pontic bonded to central incisor. Color dots for bracket orientation will soon disappear.

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3. Ceramic brackets are harder than steel and rapidly induce enamel wear of any opposing teeth. 4. Ceramic brackets are more difficult to debond than steel brackets, and wing fractures may occur easily during debracketing.33,203,218 5. The surface is rougher and more porous than that of steel brackets and hence more easily attracts plaque and stain to the surrounding enamel. 6. The added bulk required to provide adequate strength makes oral hygiene more difficult.126

Metal brackets Metal brackets rely on mechanical retention for bonding, and mesh gauze is the conventional method of providing this retention.128 Photoetched recessions or machined undercuts are also available. The area of the base itself is probably not a crucial factor regarding bond strength with mesh-backed brackets. The use of small, less noticeable metal bases helps avoid gingival irritation. For the same reason, the base should be designed to follow the tissue contour along the gingival margin. The base must not be smaller than the bracket wings, however, because of strength reasons141 and the danger of demineralization around the periphery. The mandibular molar and premolar bracket wings must be kept out of occlusion, or the brackets may come loose easily. Therefore before bonding, the operator should do the following: 1. Ask the patient to bite with teeth together; the operator then should evaluate the tooth area available for bonding. 2. Bond mandibular posterior brackets out-ofocclusion, which may necessitate adjustment bends in the arch wires. 3. Evaluate any occlusal interference on mandibular posterior attachments immediately after bonding. Occlusal tie-wings in contact with maxillary molar/premolar cusps should be spot ground (with green stone or similar). Using these procedures, the authors have been successful in routinely bonding mandibular molar and premolar attachments in children and adults. Corrosion of metal brackets may be a problem,145 and black and green stains have appeared with bonded stainless steel attachments.58,142 Crevice corrosion of the metal arising in areas of poor bonding may result from the type of stainless steel alloy used.142 However, other factors such as galvanic action, bracket base design and construction, particular oral environment, and thermal recycling of brackets109,145 may be contributing factors (for review, see von Fraunhofer233). Because of the corrosion susceptibility of stainless steel, interest is growing in the use of more corrosion-resistant and biocompatible bracket metals such as titanium (see Chapter 9).71,128,233

Gold-coated brackets Gold-coated steel brackets (see Figures 14-1, C, and 14-23) have been introduced and have gained considerable popularity, particularly for maxillary premolars and for mandibular anterior and posterior teeth. In lack of entirely satisfactory tooth-colored or clear brackets, the gold-coated brackets may be regarded as an esthetic improvement over stainless steel attachments, and they are neater and thus more hygienic than ceramic alternatives. Patient acceptance of gold-coated attachments is generally positive. In the authors’ own practices, gold-coated brackets are being used increasingly, particularly for adults (see Figures 14-23 and 14-59). Side effects in the form of corrosion or other adverse effects have not been observed clinically, at least not with the pioneer brand of gold-coated brackets (Gold’n Braces Inc., Palm Harbor, Florida).

Bonding to crowns and restorations Many adult patients have crown and bridge restorations fabricated from porcelain and precious metals in addition to amalgam restorations of molars. Banding becomes difficult, if not impossible, on the abutment teeth of fixed bridges. Recent advances in materials and techniques indicate, however, that effective bonding of orthodontic attachments to nonenamel surfaces now may be possible (for review, see Zachrisson260 and Zachrisson and Büyükyilmaz264). Particularly, the Microetcher (Danville Engineering, San Ramon, California) (Figure 14-21), which uses 50 µm white or 90 µm tan aluminum oxide particles at about 7 kg/cm2 pressure, has been advantageous for bonding to different artificial tooth surfaces. This tool is also useful for tasks such as rebonding loose brackets, increasing the retentive area inside molar bands,150 creating micromechanical retention for bonded retainers, and bonding to deciduous teeth.

Bonding to porcelain Orthodontic brackets and retainer wires may have to be fitted to adult patients who have porcelain surfaces on some teeth. Most dental ceramic and metal ceramic crowns, bridges, and veneers presently are made from different feldspathic porcelains containing from 10% to 20% aluminum oxide. However, such restorations also can be made from high-aluminous porcelains and glass ceramics.271 Conventional acid etching is ineffective in the preparation of porcelain surfaces for mechanical retention of brackets. In 1986 Wood et al.246 showed that roughening the porcelain surface, adding a porcelain primer, and using a highly filled adhesive resin when bonding to glazed porcelain added progressively to bond strength. Their in vitro findings indicated that the bond strength to porcelain equaled or surpassed that obtained after bonding to acid-etched enamel of natural teeth.

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Figure 14-21

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Therefore they warned that the bond strength was high enough to damage the porcelain tooth surface during debondings. Similar concerns have been expressed by others.64,75,119-124,204 However, cracks or fractures occurring in porcelain crowns or laminate veneers during debonding by machines in laboratory studies may not reflect the clinical situation adequately. In vitro and in vivo bond strengths may differ significantly, and it is possible to debond metal and ceramic brackets clinically much more gently than is done with laboratory machines and to secure an adhesive-bracket separation with all adhesive remaining on the tooth surface. Several studies have reported that roughening of porcelain and silane treatment may produce in vitro bond strengths that also should be clinically successful64,75,84,204; however, these claims have not been verified by clinical investigations8 or by the authors’ own experiences. Furthermore, other authors have claimed that the composite-porcelain bond is mostly micromechanical and that the contribution of the silane application for a chemical bond to most feldspathic porcelains is negligible.207,208 The clinical effectiveness of single-component liquid silanes, unhydrolyzed (Porcelain Primer, Ormco, Orange, California) and prehydrolyzed (Scotchprime, 3M), have been questioned compared with a new generation of two- and three-liquid primers with separate silane coupler and acid activator.3,146 Therefore the concept of etching porcelain with hydrofluoric acid4,105,202 to provide an even more retentive

The Microetcher II is an intraoral sandblaster approved by the Food and Drug Administration that is most useful for preparing microretentive surfaces in metals and other dental materials, whenever needed. A, The appliance consists of a container for the aluminum oxide powder, a pushbutton for fingertip control, and a movable nozzle where the abrasive particles are delivered. The Microetcher is also useful for removing old composite resin and improving the retentive surface of loose brackets before rebonding (B) and the inside of the stainless steel molar bands (C).

surface is interesting to orthodontists. The most commonly used porcelain etchant is 9.6% hydrofluoric acid in gel form applied for 2 minutes. Hydrofluoric acid is strong and requires bonding separately to other teeth, careful isolation of the working area, cautious removal of gel with cotton roll, rinsing with highvolume suction, and immediate drying and bonding (Figure 14-22). The etchant creates microporosities on the porcelain surface that achieve a mechanical interlock with the composite resin.4,202 The etched porcelain will have a frosted appearance similar to that of etched enamel. As mentioned, interpretation of the results obtained in laboratory studies on bonding to porcelain is difficult. One of the reasons is that rigorous thermocycling of the bonds appears necessary to approximate the clinical reality.271 Furthermore, to be representative, the bond failures must occur in the adhesive interface and not cohesively in one of the materials to the side of the interface. Even when these requirements are met, the chairside experiences may differ significantly from the laboratory observations. Thus the authors271 recently found in vitro that two different techniques—namely, (1) hydrofluoric acid gel treatment and (2) sandblasting and silane (Scotchprime)—produced equally strong bonds to a feldspathic porcelain. The authors’ clinical experience is considerably different. Sandblasting and silane bonds have been found to be unreliable, with unacceptably high failure rates, whereas the hydrofluoric acid

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D

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Figure 14-22 Technique for bracket bonding to porcelain surfaces includes reliable soft tissue retraction and bonding of the crown separately from other teeth. An area slightly larger than the bracket base is deglazed (A and B) before the hydrofluoric acid etching gel is applied for 2 minutes (C). The gel is removed with cotton roll (D), and the teeth are rinsed with water and air spray under high-volume suction (E). F shows final result.

gel–conditioned bonds to porcelain have proved to be excellent throughout full routine orthodontic treatment periods (Figures 14-23 and 14-24). In the authors’ hands, the addition of silane (Scotchprime) after sandblasting and hydrofluoric acid treatment did not influence the bond strengths significantly (failure rates of 8.2% versus 8.6%). For optimal bonding of orthodontic brackets and retainer wires to porcelain surfaces, the following technique is recommended (see Figure 14-22): 1. Isolate the working field adequately; bond the actual crown separately from the other teeth.

2. Use a barrier gel such as Kool-Dam (Pulpdent, Watertown, Massachusetts) (Figure 14-25) on mandibular teeth and whenever a risk exists that the hydrofluoric acid etching gel may flow into contact with the gingiva or soft tissues. 3. Deglaze an area slightly larger than the bracket base by sandblasting with 50-µm aluminum oxide for 3 seconds. 4. Etch the porcelain with 9.6% hydrofluoric acid gel for 2 minutes. 5. Carefully remove the gel with cotton roll and then rinse using high-volume suction.

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D

Figure 14-23 Orthodontic attachment bonded to porcelain-fused-to-metal crown on the left first mandibular molar in an adult female patient after hydrofluoric acid gel conditioning. Clinical appearance at start (A), during (B and C), and after treatment (D). Note that the molar bracket tolerated a solid rectangular stainless steel arch wire and heavy Class II elastic force (C) without coming loose.

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Figure 14-24 Five-unit maxillary lingual retainer bonded to porcelain and amalgam restorations. A, Occlusal view before treatment. B, The left lateral incisor is the abutment of a three-unit metal-ceramic bridge, and the right canine has a large amalgam restoration.

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Figure 14-25 A and B, When hydrofluoric acid gel is used close to the gingival margin, particularly in the mandible, one must use a light-cured blockout resin such as Kool-Dam to protect the soft tissues from the acid. C, A lower molar bracket must be positioned out of occlusion with the opposing teeth to avoid bracket loosening. If this is not possible, the tie-wing in contact with the upper molar (usually the distal wing) should be ground with green stone.

6. Immediately dry with air, and bond bracket. The use of a silane is optional. Hydrofluoric acid will not be effective for bonding to high-alumina porcelains and glass ceramics,22 and new technique improvements are needed for successful orthodontic bonding to such teeth. A newly introduced alternative technique to the use of hydrofluoric acid gel may be silica coating,192 but further clinical trials are needed to obtain experience with the silica coating technique. At debonding a gentle technique is necessary to achieve failure at the bracket-adhesive interface and avoid porcelain fracture. A 45-degree outward peripheral force should be applied to the gingival tie-wings of twin metal brackets with an anterior bond-removing plier (see Figure 14-39) or the wings should be squeezed. The residual adhesive can be removed with a tungsten carbide bur. Ceramic brackets that do not come off easily can be ground away with diamond instruments and adequate cooling.234 The porcelain surface is restored in a two-step procedure. Smoothing is achieved with slow-speed polishing rubber wheels, whereas enamel-like gloss can be created by application of diamond polishing paste in rubber cups or in specially designed points incorporating such paste271 (see Figure 14-23, D).

Bonding to amalgam Improved techniques for bonding to amalgam restorations may involve (1) modification of the metal

C

surface (sandblasting, diamond bur roughening; Figures 14-26 and 14-27), (2) the use of intermediate resins that improve bond strengths (e.g., All-Bond 2 [Bisco, Schaumburg, Illinois], Enhance, and Metal Primer [Reliance Orthodontics]), and (3) new adhesive resins that bond chemically to nonprecious and precious metals (e.g., 4-methacryloxyethyl trimellitate anhydrid [4-META] resins and 10-MDP bis-GMA resins).101,265 Similar to the bonding to porcelain, apparently a positive correlation does not exist between laboratory and clinical findings when it comes to orthodontic bonding to amalgam fillings. In vitro bonds to amalgam are significantly weaker than for similar brackets bonded to enamel of extracted human teeth.49,265 However, the clinical performance with different techniques is satisfactory. In the first amalgam study in the authors’ laboratory,265 mean tensile bond strength to sandblasted amalgam tabs ranged from 3.4 to 6.4 MPa, in contrast to control bonds to human enamel of 13.2 MPa. The strongest bonds to amalgam were obtained with a 4-META adhesive (Superbond C&B, Sun Medical, Kyoto, Japan), but an intermediate resin (All-Bond 2) and Concise produced bonds that were comparable to those of Superbond C&B. A follow-up in vitro study with different intermediate primers on the three main types of dental amalgams (spherical, lathe cut, admixed) showed better results for two 4-META primers (Metal Primer [Reliance

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DB

SB

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0.1 mm

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Figure 14-26 Scanning electron photomicrographs of a sandblasted (A) and diamond bur–roughened (B) metal surface. The use of the Microetcher for about 3 seconds (SB) provided excellent micromechanical retention, whereas periodic ridges and grooves produced by medium-grit diamond bur (DB) have few undercuts for mechanical retention. Bar is 0.1 mm.

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Figure 14-27

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A, During air abrasion, high-velocity evacuation is necessary. B and C, Intraoral sandblasting of amalgam restorations produces frosted appearance, indicating increased micromechanical retention (see Figure 14-26, A). D and E show convertible cap removal on attachment bonded to amalgam only on mandibular first molar and indicate strength of bond.

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Probability of failure (%)

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b ANA 2000 (lathe-cut)

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c Tytin (spherical)

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5

10

15 Stress (MPa)

Figure 14-28 Tensile bonded strengths of three types of amalgam tested with different intermediate resins (A) and Weibull curves demonstrating the bond failure at any chosen level of stress (B). Note the difference in reliability (steeper slope of curve) between the spherical (c) and lathe-cut (b) amalgams. AB2, All-Bond 2; AP, Amalgambond-Plus; RMP, Reliance Metal Primer. (From Büyükyilmaz T, Zachrisson BU: Improving orthodontic bonding to silver amalgam. II. Lathe-cut, admixed and spherical amalgams with different intermediate resins, Angle Orthod 68(4):337, 1998.)

Orthodontics], Amalgambond-Plus [Parkell, Farmingdale, New York) than for All-Bond 2 (Figure 14-28).49 Clinical observations since February 1996 have confirmed these results. One must emphasize that all bracket tie-wings were kept out of occlusion by placement or grinding off tie-wings in occlusion. The following procedure is recommended for bonding to amalgam:

Small amalgam filling with surrounding sound enamel 1. Sandblast the amalgam alloy with 50-µm aluminum oxide for 3 seconds (see Figure 14-27, A to C). 2. Condition surrounding enamel with 37% phosphoric acid for 15 seconds. 3. Apply sealant and bond with composite resin. Make sure bonded attachment is not in occlusion with antagonists.

Large amalgam restoration or amalgam only (Figure 14-27; see also Figure 14-27) 1. Sandblast the amalgam filling with 50-µm aluminum oxide for 3 seconds. 2. Apply a uniform coat of Reliance Metal Primer and wait for 30 seconds (or use another comparable primer according to manufacturer’s instruction). 3. Apply sealant and bond with composite resin. Make sure the bonded attachment is not in occlusion with antagonists.

Of course, amalgam surfaces can be repolished easily with rubber cups and points after debonding.

Bonding to gold In contrast to bonding to porcelain and amalgam, excellent bonding to gold crowns does not yet seem to be available to orthodontic clinicians. This is surprising in light of the high bond strengths, which generally have been reported in different laboratory studies to gold alloys.50,61,120,157,246 Different new technologies—including sandblasting, electrolytic tin-plating or plating with gallium-tin solution (Adlloy),61,157 the use of several different types of intermediate primer, and new adhesives that bond chemically to precious metals (Superbond C&B, Panavia Ex and Panavia 21 [Kuraray America, New York, New York])264—have been reported to improve bonding to gold in laboratory settings. However, the high in vitro bond strengths to gold alloys have not been confirmed by satisfactory clinical results when bonding to gold crowns. In the authors’ experience, even a combination of intraoral sandblasting coupled with the use of All-Bond 2 or 4META primers and followed by bracket bonding with composite resin or special metal-bonding adhesives may not withstand optimally the occlusal forces in clinical practice. Tin plating is not approved by the Food and Drug Administration for intraoral use.157 Clinical studies are hampered by the fact that bracket bonding to gold restorations or retainer bonding to lingual metal-ceramic crowns (Figure 14-30) is not occurring frequently in daily practice.

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D

Figure 14-29 Orthodontic attachments bonded to large amalgam restorations on maxillary first and mandibular first and second molars in an adult Class III patient before (A), during (B and C), and after treatment (D). Note that super-elastic (B) and rectangular stainless steel arch wires (C) were bent over at the distal of the second molar during treatment without coming loose.

A

B

Figure 14-30 Bonding to tooth surfaces of gold alloy include bracket bonding to molar crowns (A) and retainer wire bonding to the lingual of metal-ceramic crowns (right and left lateral incisors and right central incisor in B. If unfilled 4-methacryloxyethyl trimellitate anhydrid resin is used for retainer bonding, it may be covered with more abrasion-resistant composite resin. (From Büyükyilmaz T, Zachrisson YØ, Zachrisson BU: Improving orthodontic bonding to gold alloy, Am J Orthod 108:510, 1995.)

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Bonding to composite restoratives The bond strength obtained with the addition of new composite to mature composite is substantially less than the cohesive strength of the material.119 However, brackets bonded to a fresh, roughened surface of old composite restorations appear to be clinically successful in most instances.130 Use of an intermediate primer is probably advantageous as well.119

Lack of clinical relevance in laboratory studies on bonding It follows from the previous statements about bonding to nonenamel tooth surfaces that clinical observations rarely corroborate laboratory findings. Several reasons explain this controversy: 1. Different type of load: The debonding force used in most in vitro studies is a continuously increasing load applied to the brackets until they come loose. This load may not be representative for the force applications that occur in the oral cavity. 2. Different debonding technique: The easiest and safest method to remove metal bonded brackets clinically is to rely on the low resistance to peel force.165 By peripheral concentration of the force, the brackets come off at low load levels, with little or no force applied to the tooth. The bonding base will peel from the adhesive, creating a cohesive failure and leaving adhesive on the tooth. Debonding in machines generally is done with pure shear or tensile force applications at much higher loads, and the average stress does not characterize bond strength adequately.127 3. Different environment: The complex oral environment, with continually changing

temperature, stresses, humidity, acidity, and variations in amount and composition of plaque, is not reproducible in the laboratory.165 Therefore extrapolations from laboratory to clinical settings on bonding to enamel and nonenamel surfaces should not be made. Laboratory testing is needed primarily to find out which new products are worth testing on patients, but only successful clinical performance of such products over an adequate period of time can provide final proof of efficiency.

Lingual Attachments A drawback when bonding brackets on the labial surface, compared with banding, is that conventional attachments for control during tooth movement (e.g., cleats, buttons, sheaths, eyelets) are not included. In selected instances such aids may be bonded to the lingual surfaces to supplement the appliance (Figures 14-31 and 14-32). Particularly the palatal intrusion technique is an efficient and simple way to correct excessive distal inclination of maxillary second molars sometimes occurring after distalization of first molars. When the second molar palatal cusp is too prominent or, in more extreme cases, in buccal crossbite, correction with a buccal appliance alone is difficult or almost impossible because a combination of intrusion, buccal root torque, and palatal crown movement is needed to avoid balancing aside interferences.135 Because bonded lingual attachments may be swallowed or aspirated if they come loose, cleats are preferred to buttons. Cleats may be closed with an instrument over the elastic module or steel ligature. The bonding of brackets to the lingual surfaces of teeth is discussed separately.

A

B

Figure 14-31 Bonding lingual cleats. A, Cleats may be needed in addition to brackets when the maxillary first molars have been distalized with headgear and the premolars follow the molar. B, Another clinical situation in which bonding cleats are useful.

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Figure 14-32 The palatal intrusion technique for simultaneous intrusion, buccal root torque, and palatal crown movement of tipped maxillary second molars uses a cleat bonded to the lingual surface of the maxillary second molar, pulling it to a soldered spur on a modified transpalatal arch (A and B). In extreme cases (D), the second molar may be in buccal crossbite. B diagrams the resulting force system. (From Kucher G, Weiland FJ: Goal-oriented positioning of upper second molars using the palatal intrusion technique, Am J Orthod 110:466, 1996.)

Ligation of Bonded Brackets In contrast to brackets on bands, bonded brackets will not withstand heavy pull into arch wires. Therefore to learn a few clinical tips on correct ligation is important. Although elastic rings are time saving, they are plaque-attractive to the extent that their use is contraindicated if one aims at excellent oral hygiene and healthy gingival conditions in the patients. Steel ties are safer than elastomers and definitely are more hygienic.85,263 The rule of thumb in ligation is that the ligature wire should be twisted with the strand that crosses the arch wire closest to the bracket wing (Figure 14-33). This tightens the ligature when the end is tucked under the arch wire. To perform active ligations without pulling off any brackets, the operator should push the arch wire into the bottom of the bracket slot using the fingers (for flexible wires) and pliers or ligature director for stiffer wires,

and then make a passive ligation. If full engagement is not possible, the ligature can be retied at the next visit or elastomers can be added. Several type of Ligature-less, self-ligating, low-friction brackets have become available in recent years (e.g., SPEED System [Strite Industries, Cambridge, Ontario] and Damon SL [Ormco]). The popularity of these brackets seems to be increasing.128 Such brackets may offer the advantages of saving time, reducing friction, and probably increasing patient comfort.

Indirect Bonding Several techniques for indirect bonding are available. Most are based on the procedures introduced by Silverman and Cohen.196,198 In these techniques, the brackets are glued with a temporary material to the teeth on the patient’s models, transferred to the mouth

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A

B

C

D

Figure 14-33 Technique for active ligation to bonded brackets. A and B, A bend in the rectangular arch wire is made to correct a contact point in the maxillary incisor region. The arch wire is pushed with pliers or finger toward the base of the bracket slot before a passive ligation is made. The ligature wire should be twisted so that the strand that goes over the arch wire closest to the bracket wing (C and D). When not complete, the ligature is tightened at the next appointment.

with some sort of tray into which the brackets become incorporated, and then bonded simultaneously with a bis-GMA resin (Figure 14-34). However, most current indirect bonding techniques are based on a modification introduced by Thomas.219 In this technique, the brackets are attached to the model teeth with composite resin to form a custom base (Figure 14-35). A transfer tray of silicone putty or thermoplastic material is used, and the custom bracket bases then are bonded to the teeth with chemically cured sealant. The main advantage of indirect compared with direct bonding is that the brackets can be positioned more accurately in the laboratory and the clinical chair time is decreased. However, the method is technique-sensitive, and the chairside procedure is more crucial, at least for inexperienced clinicians; removal of excess adhesive can be more difficult and more time consuming with some techniques; the risk for adhesive deficiencies under the brackets is greater; the risk for adhesive leakage to interproximal gingival areas can disturb oral hygiene procedures; and the failure rates with some methods seem to be slightly higher.131,173,263 Only about 10% of

orthodontists in the United States use indirect bonding techniques at present.128 Reasons for differences in bond strength between direct and indirect bonding techniques,263 if any,2 may be as follows: (1) the bracket bases may be fitted closer to the tooth surfaces with one-point fitting by a placement scaler (Figure 14-11) than when a transfer tray is placed over the teeth, and (2) a totally undisturbed setting is obtained more easily with direct bonding. However, when correct technique is used, failure rates with direct and indirect bonding fall within a clinically acceptable range. At present, the individual practitioner may use either method based on practice routine, auxiliary personnel, and clinical ability and experience. For instance, indirect bonding is more likely to be used when all brackets are placed at one time at the start of treatment than with a progressive strap-up. In lingual orthodontics the indirect technique also is a prerequisite for good bracket alignment5 because direct visualization has evident difficulties. Although bracket placement in the laboratory may suggest more accurate positioning, this has not been

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Figure 14-34

E

confirmed in studies comparing direct and indirect bonding. Koo et al.134 found no difference regarding angulation or mesiodistal bracket position between direct bonding with light-cured composite resin and an indirect technique, although bracket height placement for indirect bonding was better. The differences were small, and it is questionable whether they are clinically significant. Aguirre et al.2 showed that neither direct nor indirect techniques resulted in 100% accuracy of bracket positioning. More recent computer-assisted measuring devices for indirect bonding (see Lingual Bracket Bonding: Invisible Braces) may improve the accuracy of bracket placement and take into account anatomic variations, overcorrections, and mechanical deficiencies of preadjusted appliances.148,240,241

Indirect bonding with a silicone transfer tray. A, Brackets attached to plaster model. B and C, Tray (hard Optosil, DynaFlex, St. Louis, Missouri). Note the brackets and the orientation mark in the midline. D, Etching of the right and left sides simultaneously. Note the difference in appearance between the central and cervical portions of the enamel. E, Final appearance following careful cleanup with instruments and a tungsten carbide bur. The first premolars were referred for extraction at this stage. (Courtesy BO Brobakken, Oslo, Norway).

Several products have been introduced recently that are specifically designed for indirect bonding procedures. Different types of custom base composites may be light cured, chemically cured, or thermally cured.130,173 One system (from Reliance Orthodontics) recommends the use of thermally cured base composite (Therma-Cure), Enhance adhesion booster, and a chemically cured sealant (Custom I.Q.). Another system (from 3M/Unitek) recommends the use of light-cured base composite (Transbond XT) and chemically cured sealant (Sondhi Rapid Set) in the clinic (Figure 14-36). Studies comparing the in vitro bond strengths obtained with these two indirect systems compared with direct bonding with light-cured composite resin (Transbond XT) indicate that the differences between the indirect and direct methods are small and

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A

B

C

D

E

F

Figure 14-35 Indirect bonding using a clear tray (Memosil, Heraeus Kulzer, Armonk, New York) and a light cure adhesive.

probably of little clinical significance. Using single bracket trays for transfer, Klocke et al.130 found that indirect bonding with Sondhi Rapid Set showed bond strength similar to direct bonding with Transbond XT, whereas indirect bonding with Custom I.Q. showed lower bond strengths. However, Polat et al.,173 using full-arch transfer trays of putty silicone material, found higher bond strength when they used thermally cured bracket bases indirectly bonded with Custom I.Q. than with lightcured bases (Transbond XT) bonded with Sondhi Rapid Set. In a clinical test for 9 months in 15 patients whose teeth were indirectly bonded with either of the two

techniques (thermally cured bases bonded with Custom I.Q. or light-cured bases bonded with Sondhi Rapid Set) using a split-mouth design, no significant differences in bond failure rates were found.

Clinical procedure As mentioned, several indirect bonding techniques have proved reliable in clinical practice (see Figures 14-34 to 14-36). The techniques differ in the way the brackets are attached temporarily to the model, the type of transfer tray used (e.g., full-arch, sectioned full-arch, single tooth, and double-tray system74), the sealant or resin

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C

D

E

F

Figure 14-36 Indirect bonding using light-cured base composite (Transbond XT) and chemically cured sealant (Sondhi Rapid Set). See text for details.

used, whether segmented or full bonding is used, and the way the transfer tray is removed so as not to exert excessive force on a still-maturing bond.

Indirect bonding with composite custom bracket base Most current techniques are modifications of the Thomas219 technique, which means using composite resin custom bracket bases (light cured, thermally cured, or chemically cured), and a chemically cured sealant as the clinical bonding resin. The following

procedure may be useful (see Figure 14-36): 1. Take an impression and pour up a stone (not plaster) model. 2. Select brackets for each tooth. 3. Isolate the stone model with a separating medium. 4. Attach the brackets to the teeth on the model with light-cured or thermally cured composite resin, or use adhesive precoated brackets. 5. Check all measurements and alignments. Reposition if needed.

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6. Make a transfer tray for the brackets. Material can be putty silicone, thermoplastics, or similar. 7. After removing the transfer trays, gently sandblast the adhesive bases with a microetching unit, taking care not to abrade the resin base.205 8. Apply acetone to the bases to dissolve the remaining separating medium. 9. Prepare the patient’s teeth as for a direct application. 10. Apply Sondhi Rapid Set resin A to the tooth surfaces and resin B to the bracket bases. (If Custom I.Q. is used, apply resin B to the teeth and resin A to the bases). 11. Seat the tray on the prepared arch and with the fingers apply equal pressure to the occlusal, labial, and buccal surfaces. Hold for a minimum of 30 seconds, and allow for 2 minutes or more of curing time before removing the tray. 12. Remove excess flash of resin from the gingival and contact areas of the teeth with a scaler or contraangle handpiece and tungsten carbide bur.

Lingual Bracket Bonding: Invisible Braces When it became apparent into late 1970s that bonding of brackets was a viable procedure and that esthetic plastic and ceramic brackets were a compromise, placing the brackets on the lingual surfaces of the teeth appeared to be the ultimate esthetic approach (Figures 14-1 and 14-37). The technique rapidly gained popularity in the early 1980s, but most clinicians experienced considerable difficulties, particularly in the finishing stages,12 and abandoned the technique for routine use.128 The development was pioneered in Japan by Fujita,88 who worked on the mushroom arch, and some American orthodontists: Kurz (cited in Alexander et al.5), Gorman and Smith,98 and Creekmore.67 Although treating

malocclusions successfully from the lingual side is possible,12,88,98,241,242 a combined lingual and buccal segmental approach may offer a number of options with no great esthetic compromises in most patients. Surprisingly, the problem with lingual orthodontics is not that brackets become loose but rather that some pronunciation difficulties111 occur immediately after insertion (although the difficulties vary individually and may disappear within a few weeks88). Furthermore, the technique is difficult and time consuming, and the working position is awkward.12,88 More precision is necessary for the adjustment of lingual arch wires, with reduced interbracket distance. If the lingual treatment is to become more important in the future than at present,128 additional improvements in bracket design and technical aids are needed. Such changes are under way. Progress in practicability for lingual orthodontics is due to optimization of the laboratory and chairside procedures together with computerized arch wire fabrication and use of sophisticated materials.240 Customized brackets (Figure 14-38) are produced after scanning the malocclusion model from various perspectives, using a high-resolution optical three-dimensional scanner. The brackets are designed individually in the computer, are optimally positioned, and subsequently are fabricated using computer-aided design/computer-aided manufacturing technology. The bracket bases have exact form-fit properties and later are locked positively with the lingual surfaces of the teeth, permitting direct rebonding should they come loose. The bracket bodies of the customized brackets have a lower profile than that of current prefabricated lingual brackets (see Figure 14-37). The testing of various slot types has shown a vertical slot with a vertical insertion direction to be optimal (see Figure 14-38, B and C). High-end rapid prototyping machines are used to convert the virtual bracket series into a wax analog that then is cast into hard alloy with high gold content. The exact location of the bracket slots is known and transmitted to a bending robot through the export of slot coordinate systems. The robot operates with two grasping tools and can bend arch wires precisely in highly complex geometries. The superelastic arch wires are reprogrammed thermally during the actual bending process to ensure precision manufacturing.240 This lingual technique can provide excellent treatment results with but little (first-order) wire bending in the clinic.240,241

Rebonding

Figure 14-37 Lingual bracket bonding with seventh-generation Ormco brackets. (Courtesy D Wiechmann, Bad Essen, Germany).

Bonded brackets that become loose during treatment consume much chair time, are poor publicity for the office, and are a nuisance to the orthodontist. The best way to avoid loose brackets is to adhere strictly to the rules for good bonding mentioned previously. Use of a quick technique for rebonding loose brackets also is important.

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B A

Figure 14-38 Customized brackets for lingual orthodontic treatment. A to C, Digital setup with individually defined bracket bases. (Courtesy D Wiechmann).

C

A loose metal bracket is removed from the arch wire. Any adhesive remaining on the tooth surface is removed with a tungsten carbide bur. The adhesive remaining on the loose bracket is treated by sandblasting (see Figure 14-21) until all visible bonding material is removed from the base. The tooth then is etched with Ultraetch 35% phosphoric acid gel for 15 seconds. On inspection the enamel surface may not be uniformly frosty because some areas still may retain resin. The phosphoric acid will reetch any exposed enamel and remove the pellicle on any exposed resin. After priming, the bracket is rebonded. The neighboring brackets are religated first, and then the rebonded bracket is ligated. The bond strength for sandblasted rebonded brackets is comparable to the success rate for new brackets.206 A loose ceramic bracket should be replaced with a new, intact bracket for optimum bond strength.

Recycling Several methods of recycling debonded attachments for repeat use, by commercial companies or by a duplicated procedure in office, are available.139 The main goal of the recycling process is to remove the adhesive from the bracket completely without damaging or weakening the delicate bracket backing or distorting the dimensions of the bracket slot. Recycling of brackets has dropped off considerably over the past years and now is done by only 4% of orthodontists in the United States.128 Commercial processes use heat (about 450° C) to burn off the resin, followed by electropolishing to remove the oxide buildup (e.g., Esmadent), or they use solvent stripping combined with high-frequency vibrations and only flash electropolishing (e.g., Ortho-Cycle). The electropolishing is needed for removal of any tarnish or oxide

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formed during the elimination of the adhesive from the clogged pad. Buchman42 published photomicrographs showing microstructural changes after thermal treatment that were correlated with a decrease in corrosion resistance and hardness. Changes in torque angle and slot size after one or two recyclings were below clinical significance.42,107

Conclusion Bonding of brackets has changed the practice of orthodontics and has become a routine clinical procedure in a remarkably short time.128 Modifications of technical devices, sealants and adhesives, attachments, and procedures are continuing. Careful study of the available information by the orthodontist will be mandatory in keeping up with progress. However, cautious interpretation of in vitro studies is recommended because the in vivo results do not always reflect and verify the laboratory findings. Long-term follow-up studies are needed in several areas. At present the authors are using bonded brackets routinely on all teeth except maxillary first molars. In most routine situations, banding maxillary first molars provides a stronger attachment and availability of lingual sheaths (such as for transpalatal bars, elastics, and headgear) and may give some interproximal caries protection. Finally, the procedure described for bonding mandibular second and third molars has proved to be successful in clinical use over many years. This is particularly true in adolescents, whose teeth are erupting during the course of treatment. The mandibular second molar is better suited for bonding than for banding because gingival emergence of the buccal surface precedes emergence of the distal surface.

DEBONDING The objectives of debonding are to remove the attachment and all the adhesive resin from the tooth and restore the surface as closely as possible to its pretreatment condition without inducing iatrogenic damage. To obtain these objectives, a correct technique is of fundamental importance. Debonding may be unnecessarily time consuming and damaging to the enamel if performed with improper technique or carelessly. Because several aspects of debonding are controversial, debonding is discussed in detail as follows: • Clinical procedure • Characteristics of normal enamel • Influence of different debonding instruments on surface enamel • Amount of enamel lost in debonding • Enamel tearouts

• Enamel cracks (fracture lines) • Adhesive remnant wear • Reversal of decalcifications

Clinical Procedures Although several methods have been recommended in the literature for bracket removal and adhesive cleanup,* and some discrepancy of opinion still exists, the techniques described have proved successful in the authors’ experience. Their rationales are mentioned throughout the ensuing discussion. The clinical debonding procedure may be divided in two stages: 1. Bracket removal 2. Removal of residual adhesive

Bracket removal: steel brackets Several different procedures for debracketing with pliers are available. An original method was to place the tips of a twin-beaked pliers against the mesial and distal edges of the bonding base and cut the brackets off between the tooth and the base. Several pliers are available for this purpose. A gentler technique is to squeeze the bracket wings mesiodistally and lift the bracket off with a peel force. This is particularly useful on brittle, mobile, or endodontically treated teeth. The brackets are deformed easily and are less suitable for recycling when the latter method is used. The recommended technique, in which brackets are not deformed, is illustrated in Figure 14-39. This technique uses a peeling-type force, which is most effective in breaking the adhesive bond. A peel force, as in peeling an orange, creates peripheral stress concentrations that cause bonded metal brackets to fail at low force values.165 The break is likely to occur in the adhesivebracket interface, thus leaving adhesive remnants on the enamel. Attempts to remove the bracket by shearing it off (as is done in removing bands) can be traumatic to the patient and potentially damaging to the enamel.

Bracket removal: ceramic brackets With the introduction of ceramic brackets a new concern over enamel fracture and loss from debonding has arisen.13,178 Because of differences in bracket chemistry and bonding mechanisms, various ceramic brackets behave differently on debonding. For example, ceramic brackets using mechanical retention cause fewer problems in debonding than do those using chemical retention.32,178,231,245 In this regard, some knowledge about the normal frequency, distribution, and orientation of enamel cracks in young and in older teeth is important.

*References 41, 45, 54, 56, 104, 113, 167, 178, 181, 221, 262.

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B

A

Figure 14-39 Bracket removal with pliers. Still ligated in place, the brackets are gripped one by one with 095 Orthopli bracket-removing pliers and lifted outwardly at a 45-degree angle. The indentation in the pliers fits into the gingival tie-wings for a secure grip. This is a quick and gentle technique that leaves the brackets intact and fit for recycling, if so desired. A, The bond breaks in the adhesive-bracket interface, and the pattern of the meshbacking is visible on the adhesive remaining on the teeth. B, Same technique for maxillary steel brackets.

Ceramic brackets will not flex when squeezed with debonding pliers. The preferred mechanical debonding is to lift the brackets off with peripheral force application, much the same as for steel brackets (see Figure 14-39). Several tie-wings still may fracture, which in practice requires grinding away the rest of the bracket.178 Cutting the brackets off with gradual pressure from the tips of twin-beaked pliers oriented mesiodistally close to the bracket-adhesive interface is not recommended because it might introduce horizontal enamel cracks. More recent ceramic brackets have a mechanical lock base and a vertical slot that will split the bracket by squeezing. Separation is at the bracket-adhesive interface, with little risk of enamel fracture.34 Low-speed grinding of ceramic brackets with no water coolant may cause permanent damage or necrosis of dental pulps. Therefore water cooling of the grinding sites is necessary. High-volume suction and eye protection also are recommended to reduce the number of ceramic particles spread about the operatory area.234 Finally, thermal debonding32,66,122,188,211 and the use of lasers140,183,225 have the potential to be less traumatic and less risky for enamel damage, but these techniques are still at an introductory stage.

Removal of residual adhesive Because of the color similarity between present adhesives and enamel, complete removal of all remaining adhesive is not achieved easily. Many patients may be left with incomplete resin removal,83 which is not acceptable. Abrasive wear of present bonding resins is limited,41 and remnants are likely to become unesthetically discolored with time. The removal of excess adhesive may be accomplished by (1) scraping with a sharp band or bond-removing

Figure 14-40 Adhesive remaining after debracketing may be removed with a tungsten carbide bur at about 30,000 rpm.

pliers or with a scaler251 or by (2) using a suitable bur and contraangle (Figure 14-40). Although the first method is fast and frequently successful on curved teeth (premolars, canines), it is less useful on flat anterior teeth. A risk also exists of creating significant scratch marks. The preferred alternative262 is to use a suitable dometapered tungsten carbide bur (#1171 or #1172) in a contraangle handpiece (see Figure 14-39). Clinical experience and laboratory studies262 indicate that about 30,000 rpm is optimal for rapid adhesive removal without enamel damage. Light painting movements of the bur should be used so as not to scratch the enamel. Water cooling should not be used when the last remnants are removed because water lessens the contrast with enamel. Speeds higher than 30,000 rpm using fine

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fluted tungsten carbide burs54,113 may be useful for bulk removal but are not indicated closer to the enamel because of the risk of marring the surface.104,113,262 Even ultrafine high-speed diamonds produce considerable surface scratches.113 Slower speeds (10,000 rpm and less) are ineffective, and the increased jiggling vibration of the bur may be uncomfortable to the patient. When all adhesive has been removed, the tooth surface may be polished with pumice54 (or a commercial prophylaxis paste) in a routine manner. However, in view of the normal wear of enamel, this step may be optional.

CHARACTERISTICS OF NORMAL ENAMEL Apparently not every clinician is familiar with the dynamic changes that continuously take place throughout life in the outer, most superficial enamel layers.143,200 Because a tooth surface is not in a static state, the normal structure differs considerably between young, adolescent, and adult teeth.143 Normal wear must be considered in any discussion of tooth surface appearance after

debonding. The characteristics are visible on the clinical and microscopic levels. The most evident clinical characteristics of young teeth that have just erupted into the oral cavity are the perikymata* that run around the tooth over its entire surface (Figure 14-41). By scanning electron microscopy the open enamel prism ends are recognized as small holes.262 In adult teeth the clinical picture reflects wear and exposure to varying mechanical forces (e.g., toothbrushing habits and abrasive foodstuffs). In other words, the perikymata ridges are worn away and replaced by a scratched pattern (Figure 14-42). Frequently, cracks are visible. Scanning electron microscopy shows no evidence of prism ends or perikymata; instead deep and finer scratches run across the surface141,262 (Figure 14-43, see also Figure 14-42). Teeth in adolescents reflect an intermediate stage (see Figure 14-43). According to

*The use of the enamel surface terms perikymata and imbrications/ imbrication lines in the dental literature is inconsistent and confusing. The present terminology is based on Risnes S: Rationale for consistency in the use of the enamel surface terms: perikymata and imbrications, Scand J Dent Res 92:1, 1984.

A

Enamel Prism Ends

B

C

Figure 14-41 A, Typical perikymata in a 10-year-old boy. B, Scanning electron microscopy appearance (×50.) C, Enlargement of the central portion in B, showing numerous small pits (the typical signs of enamel prism ends) and a crack. P, Perikymata.

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Horizontal Scratches No Perikymats No Prism Ends FS

DS

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B DS

Figure 14-42 A, In adult teeth the perikymata remain in developmental grooves. Note the other irregularities: vertical and horizontal scratches, pits, internal white spots, vertical cracks (B) (scanning electron micrograph, ×50). Neither perikymata nor prism end openings are visible. However, note the severe horizontal scratches. Most are fine (FS), but some are coarser and deeper (DS).

A

B

C

P S S

Figure 14-43 Scanning electron micrographs of normal enamel in young (A), adolescent (B), and adult (C) teeth. Note the gradual transition from virgin tooth with perikymata (P) and open prism ends to a gradually increasing scratched (S) appearance. (Scale division is 0.1 mm.) (B and C Courtesy F Mannerberg, Malmö, Sweden.)

615

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Green rubber wheel

Sand paper disk

A

B

TC-bur + pumice (replica)

TC- bur

P

C

D

Figure 14-44 Comparison of the effect of three debonding techniques on the enamel surface. A to C, Scanning electron micrographs after adhesive removal without subsequent polishing (×50). Note that the scratches are of similar appearance in A and B but that in C only slight faceting with fine scratches (open arrows) is intermingled with the perikyma ridges (P). D, Same area as in C in replica after pumicing. The surface is smoother (arrows).

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Chapter 14 • Bonding in Orthodontics Mannerberg,143 at 8 years of age practically all teeth show evident perikymata on one third to two thirds of the tooth surface; at age 13, the number is reduced to 70% to 80%; and at age 18, only 25% to 50% of teeth demonstrate such ridges. Using a replica technique to study the gradual removal of artificial scratch marks on the teeth, Mannerberg found the normal wear to range from 0 to 2 µm per year. For comparison, a sandpaper disk that touches the enamel only a fraction of a second will leave scratch marks at least 5 µm deep.

Influence on Enamel by Different Debonding Instruments By proposing an enamel surface index with five scores (0 to 4) for tooth appearance and using replica scanning electron microscopy and step-by-step polishing, Zachrisson and Årtun262 were able to compare different instruments commonly used in debonding procedures and rank their degrees of surface marring on young permanent teeth. The study demonstrated that (1) diamond instruments were unacceptable (score 4), and even fine diamond burs produced coarse scratches176 and gave a deeply marred appearance; (2) medium sandpaper disks and a green rubber wheel produced similar scratches (score 3) (Figure 14-44) that could not be polished away; (3) fine sandpaper disks produced several

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considerable and some even deeper scratches and a appearance largely resembling that of adult teeth (score 2); (4) plain cut and spiral fluted tungsten carbide burs operated at about 25,000 rpm were the only instruments that provided the satisfactory surface appearance (score 1); however, (5) none of the instruments tested left the virgin tooth surface with its perikymata intact (score 0). The clinical implication of the study is that tungsten carbide burs produced the finest scratch pattern with the least enamel loss and are superior in their ability to reach difficult areas (Figure 14-45): pits, fissures, and along the gingival margin. For optimal efficiency the bur must be replaced when it becomes blunt. Increaseddiameter burs or high-speed equipment also may be used for bulk removal.51,96 The oval tungsten carbide bur is useful for removing adhesive remnants after debonding retainers and brackets on the lingual surfaces of teeth.

Amount of Enamel Lost in Debonding The orthodontic literature discusses how much enamel actually is removed in routine bonding and debonding. The amount is related to several factors, including the instruments used for prophylaxis and debonding and the type of adhesive resin used.73,176,221,232,262 An initial prophylaxis with bristle brush for 10 to 15 seconds per tooth (which is in fact much longer than

B

Figure 14-45 A, After debonding with a tungsten carbide bur at low speed. Gentleness of technique is reflected by the evident perikymata-like pattern on debonded teeth (B). Same case as in Figure 14-63.

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that used in clinical routines) may abrade away as much as 10 µm of enamel, whereas only about 5 µm may be lost when a rubber cup is used.176,221 Cleanup of unfilled resins may be accomplished with hand instrumentation only, and this procedure generally results in a loss of 5 to 8 µm of enamel. Depending on the instruments used for prophylaxis, total enamel loss for unfilled resins may be 2 to 40 µm.176,221 Adequate removal of filled resin generally requires rotary instrumentation; the enamel loss then may be 10 to 25 µm. Pus and Way176 found that a high-speed bur and green rubber wheel remove about 20 µm and a lowspeed tungsten carbide bur removes around 10 µm of enamel. From in vitro micrometer measurements using an optical system of a profile projector and steel reference markers, total enamel loss for filled resins was estimated to be 30 to 60 µm, depending on the instruments used for prophylaxis and debonding.32,176,221 Additional deep-reaching enamel tearouts down to a depth of 100 µm and localized enamel loss of 150 to 160 µm also have been reported.73 However, using computerized three-dimensional scanning over the tooth surface, van Waes et al.232 recently confirmed the authors’ observations of a more limited loss of enamel when tungsten carbide burs are used cautiously.262 Van Waes et al.232 found an average enamel loss of only 7.4 µm and concluded that minimal enamel damage is associated with careful use of a tungsten carbide bur for removal of residual composite. In a clinical perspective the enamel loss encountered with routine bonding and debonding procedures, exclusive of deep enamel fractures or gouges resulting from injudicious use of hand instrument or burs, is not significant in terms of total thickness of enamel. The surfaces usually bonded have a thickness of 1500 to 2000 µm. The claim that removal of the outermost layer of enamel (which is particularly caries resistant and fluoride rich) may be harmful also is not in accordance with recent views on tooth surface dynamics and with clinical experience over many years. The facial tooth surfaces are left smooth and self-cleansing after debonding. Caries have been demonstrated not to develop in such sites even if the entire enamel layer is removed. Similarly, no histologic or clinical evidence of adverse effects was experienced after significant recontouring of canines that had been ground to resemble lateral incisors as long as the surfaces were left smooth and sufficient water cooling was used.222,267 In that case, about half the enamel thickness was removed.

Enamel Tearouts Localized enamel tearouts have been reported to occur associated with bonding and debonding metal73 and ceramic brackets.178 Tearouts may be related at least in part to the type of filler particles in the adhesive resin

used for bonding and to the location of bond breakage. When comparisons were made between tooth surface appearance after debonding metal brackets attached with macrofilled (10 to 30 µm) or microfilled (0.2 to 0.3 µm) adhesives, a difference occurred when the resin was scraped off with pliers. Possibly small filler particles may penetrate into the etched enamel to a greater degree than macrofillers may penetrate. For instance, the holes corresponding to the dissolved enamel prism cores in the central etch type (see Figure 14-5, A) are 3 to 5 µm in diameter. On debonding the small fillers reinforce the adhesive tags. The macrofillers, however, create a more natural break point in the enamel-adhesive interface. Similarly, with unfilled resins there is no natural break point. Ceramic brackets using chemical retention cause enamel damage more often than those using mechanical retention.32,178 This damage occurs probably because the location of the bond breakage is at the enamel-adhesive rather than at the adhesive-bracket interface.13,178 The clinical implications are (1) to use brackets that have mechanical retention and debonding instruments and techniques that primarily leave all or the majority of composite on the tooth (see Figure 14-39, A) and (2) to avoid scraping away adhesive remnants with hand instruments.

Enamel Cracks Cracks, occurring as split lines in the enamel, are common but often are overlooked at clinical examination because most are difficult to distinguish clearly without special technique; generally they do not show up on routine, intraoral photographs (Figure 14-46). Thus finger shadowing in good light or, preferably, fiberoptic transillumination is needed for a proper impression of the crack268 (see Figure 14-46). The origin of cracks is multicausal. Different forms of mechanical and thermal insult may fracture the enamel cap after eruption; this results from the significant difference in rigidity between enamel and dentin. A distinct possibility is that the sharp sound sometimes heard on removal of bonded orthodontic brackets with pliers is associated with the creation of enamel cracks. The occurrence of cracks in debonded, debanded, and orthodontically untreated teeth was discussed in a study by Zachrisson et al.268 Using fiberoptic light technique, the researchers examined more than 3000 teeth in 135 adolescents. The prevalence of cracks, their distribution per tooth, their location on the tooth surface, and the type (pronounced versus mild, horizontal versus vertical) were described. The most important findings were that (1) vertical cracks are common (in fact, more than 50% of all teeth studied had such cracks), but individual variation is great; (2) few horizontal and oblique cracks are observed normally; (3) no significant

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Figure 14-46 Enamel cracks generally are not visible on intraoral photographs. Several cracks clearly seen on the left central incisor with fiberoptic transillumination (A) are undetectable by routine photography (B). Note the vertical orientation of the cracks.

difference existed between the three groups regarding prevalence and location of cracks; and (4) the most notable cracks (i.e., those invisible under normal office illumination) are on the maxillary central incisors and canines. The clinical implication of these findings is that if an orthodontist (1) observes several distinct enamel cracks on the patient’s teeth after debonding, particularly on teeth other than maxillary canines and central incisors or (2) detects cracks in a predominantly horizontal direction, this is an indication that the bonding or debonding technique used may need improvement. With ceramic brackets, the risk for creating enamel cracks is greater than for metal brackets. The lack of ductility may generate stress in the adhesive-enamel interface that may produce enamel cracks at debonding.13 Another clinical implication may be the need for pretreatment examination of cracks, notifying the patient and the parents if pronounced cracks are present. The reason for this examination is that patients may be overly inspective after appliance removal and may detect cracks that were present before treatment of which they were unaware. They may question the orthodontist about the cause of the cracks. Without pretreatment diagnosis and documentation (most cracks are not visible on routine intraoral slides), proving that such cracks are indeed unrelated to the orthodontic treatment is almost impossible.

Abrasive wear depends on the size, type, and amount of reinforcing fillers in the adhesive. When at the time of debonding, varying amounts of adhesive purposely were left on the teeth assumed to be the most exposed to toothbrushing forces (i.e., the maxillary left canine and one neighboring tooth), the abrasion over a 12-month period was almost insignificant in clinical terms.41 Only thin films of residual adhesive showed any reduction in size. The clinical implications of leaving residual adhesive after debonding are not clear. Gwinnett and Ceen103 reported that small remnants of unfilled sealant did not predispose to plaque accumulation and did begin to wear away with time. However, this finding cannot be transferred automatically to different types of filled adhesives, some of which have much greater wear resistance and accumulate plaque more readily.263 The presence of extremely thin films of adhesive may not be of esthetic or other concern because any color change in the films probably cannot be perceived. In some instances, to seal surface irregularities such as pits and grooves may even be advantageous to protect against demineralization. Nonetheless, in light of Brobakken and Zachrisson’s findings,41 it seems too optimistic to believe that residual filled adhesive will disappear quickly by itself after debonding; it appears irresponsible to leave large accumulations of adhesive.

Adhesive Remnant Wear

Reversal of Decalcification

Frequently, adhesive has been found on the tooth surface, even after attempts to remove it with mechanical instruments.45,56,73,104 Because of color resemblance to the teeth, particularly when wet, residual adhesive easily may remain undetected.83 In other instances, adhesive may be left on purpose because the operator expects that it will wear off with time.

White spots or areas of demineralization are carious lesions of varying extent. The incidence and severity of white spots after a full term of orthodontic treatment have been studied by several authors.* The general conclusion was that individual teeth, banded or bonded, *References 97, 153, 162, 269, 270, 271.

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B

Figure 14-47 Extreme degree of enamel demineralization after orthodontic treatment in a caries-prone patient (A). Note that white spot lesions can occur on multiple teeth. B, The contour of the bonded brackets is visible on several teeth.

may exhibit significantly more white spot formation than may untreated control teeth (Figure 14-47). In a multibonded technique (with lack of any preventive fluoride program), Gorelick et al.97 found that 50% of the patients experienced an increase in white spots. The highest incidence was in the maxillary incisors, particularly the laterals. This obvious degree of iatrogenic damage suggests the need for preventive programs using fluoride associated with fixed appliance orthodontic treatment. Extensive overviews of the different methods of orthodontic fluoride administration have been presented.44,249 Daily rinsing with dilute (0.05%) sodium fluoride solution throughout the periods of treatment and retention, plus regular use of a fluoride dentifrice, is recommended as a routine procedure for all orthodontic patients.249 The weak fluoride mouth rinse is effective yet has few risks, and most patients can manage to use it easily for 1 to 2 years. Definite responsibility also must be given to the patient to avoid decalcifications during treatment. In addition, painting a fluoride varnish41 or new effective anticaries agents such as titanium tetrafluoride47 over caries-susceptible sites at each visit may be useful in patients with hygiene problems. Much evidence now exists from in vivo and in vitro studies to support the claim that small carious lesions can heal, a process usually referred to as remineralization.18,164,199,200 Dental caries may not be a process of simple continuing demineralization. Rather caries may be the result of a dynamic series of events, with remineralization occurring naturally during the formation of a carious lesion. Fluoride ions greatly enhance the degree of remineralization (incorporation of calcium and phosphate from the saliva) and reduce the time required for this mechanism to occur. Only lower levels of fluoride are required to trigger the mechanism; raising the fluoride level further does not result in a greater degree of remineralization.80,199 Other fluoride effects may be on

plaque adhesion (quantitatively and qualitatively),185 although the more traditional theory that fluoride increases enamel resistance is probably not too significant. Thus fluoride ions may be concentrated into demineralized areas, which thereby act as reservoirs promoting remineralization from the saliva. Although sufficient clinical evidence proves that the process of white spot formation can be reversed at least in part, more information is necessary before an optimal remineralization program for orthodontic patients can be established. Årtun and Thylstrup18 found that removal of the cariogenic challenge after debonding results in arrest of further demineralization, and a gradual regression of the lesion at the clinical level takes place primarily because of surface abrasion with some redeposition of minerals. However, Øgaard et al.164 observed that remineralization of surface softened enamel (such as under a loose band or bracket from one visit to another) and subsurface lesions are completely different processes. The surface-softened lesions remineralize faster and more completely than subsurface lesions, which remineralize slowly, probably because of lesion arrest by widespread use of fluoride. Visible white spots that develop during orthodontic therapy therefore should not be treated with concentrated fluoride agents immediately after debonding because this procedure will arrest the lesions and prevent complete repair. In the future, orthodontists can expect more effective methods for caries reversal to become available.47 At present it seems advisable to recommend a period of 2 to 3 months of good oral hygiene but without fluoride supplementation associated with the debonding session. This procedure should reduce the clinical visibility of the white spots. More fluoride may tend to precipitate calcium phosphate onto the enamel surface and block the surface pores, which limits remineralization to the

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B

Figure 14-48 White spot lesions before (A), and after (B), microabrasion. See text for details.

superficial part of the lesion, and the optical appearance of the white spot is not reduced.

Microabrasion When the remineralizing capacity of the oral fluids is exhausted and white spots are established (Figure 14-48 see also Figure 14-47), microabrasion is the optimal way to remove superficial enamel opacities. By the use of this technique, one can eliminate enamel stains with minimal enamel loss. Clinical procedure: A custom-made abrasive gel is prepared with 18% hydrochloric acid, fine powdered pumice, and glycerin. The active mixture is applied as follows94: 1. The gingiva is isolated using blockout resin or rubber dam. Dental floss may be useful to prevent soft tissue contact and injury from the acid. 2. The abrasive gel is applied using an electric toothbrush for 3 to 5 minutes. The original toothbrush tip is modified by cutting the peripheral bristles to create a smaller brush tip to fit on tooth surfaces better. 3. Rinse for 1 minute. To prevent enamel pitting, the acid should not be left on the tooth for an extended time. For best results, and depending on the severity of the lesions, the procedure can be repeated monthly 2 to 3 times. This makes stains disappear gradually. The microabrasion technique is effective in removing white spots and streaks and brown-yellow enamel discolorations. In cases of more extensive mineral loss, however, grinding with diamond burs under water cooling or composite restorations are inevitable.

BONDED RETAINERS Permanent maintenance of the achieved result after successful treatment of malocclusion is undoubtedly

a great, if not the greatest, problem for orthodontic clinicians. This is especially true for adult patients. Therefore the relative scarcity of literature on the subject is surprising. The use of fixed bonded retainers is increasing,128 and the various forms allow more differentiated retention than before. Bonded retainers also have other advantages: 1. Completely invisible from the front132 2. Reduced need for long-term patient cooperation 3. Long-term (up to 10 years) and even permanent retention when conventional retainers do not provide the same degree of stability The term differential retention, as introduced by James L. Jensen,117 implies that special attention is directed toward the strongest or most important predilection site for relapse in each case. Thus the most appropriate mode of retention for the postorthodontic situation in question should be used and should be based on a careful evaluation of the pretreatment diagnostic records, habits, patient cooperation, growth pattern, and age. Implicit in the introduction of the acid-etch technique for direct-bonded retainers is the provision of a variety of new methods for retention. This discussion reviews the current level of technical expertise regarding bonded retainers. Because the technique is comparatively new, any discussion of it is weakened by the evident lack of published clinical and long-term research findings with various types of retainers and splints.26 For this reason, the discussion in a large part is based on the authors’ own experiences. The following subdivisions are used: • Mandibular canine-to-canine (3-3) retainer bar • Direct contact splinting • Flexible spiral wire retainers • Hold retainers for individual teeth In the following pages, two different types of retainer wire are discussed—a thick one (0.030 or 0.032 inch) and a thin one (0.0215 inch)—with entirely different indications and modes of bonding.

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B

C

D

Figure 14-49 A, First-generation bonded mandibular lingual 3-3 retainer. B, Second-generation 3-3 retainer. C and D, Third-generation 3-3 retainer in stainless steel and gold-coated bar, respectively.

Bonded Lingual Canine-to-Canine Retainer Bar Lingually bonded 3-3 retainers can provide excellent results11,16,26,31,252 (Figure 14-49) if meticulous construction and bonding techniques are followed, along with some modifications of the original design. In differential retention philosophy the purpose of a bonded 3-3 retainer bar is (1) to prevent incisor recrowding, (2) to hold the achieved lower incisor position in space, and (3) to keep the rotation center in the incisor area when a mandibular anterior growth rotation tendency is present. The retainer bar may be indicated particularly in persons with a flat functional occlusal plane,117 open bite, Class II with rotation center in the premolar area (Björk’s anterior rotation Type III36), or Class III growth tendency. The standard appliance is bonded to the lingual surfaces of the canine teeth. The bar, which originally was constructed from plain blue Elgiloy wire with a loop at each terminal end for added retention252 (see Figure 14-49, A) was replaced by a similar-diameter multistrand wire (see Figure 14-49, B). For some patients, this wire proved not solid enough and distorted, and the wire was difficult to bend to optimal fit. These drawbacks are eliminated in the third-generation design (see Figure 14-49, C and D), in which the bar is made from round

0.032-inch stainless steel or 0.030-inch gold-coated wire,259 sandblasted on the ends for improved micromechanical retention. Bonding is done with a chemically or light-cured composite resin because such adhesives provide the strongest bonds257and show comparatively little abrasion over extended periods.27,41 In selected cases when the lower first premolars at the start of treatment are blocked out labially, severely rotated, or tipped, extention of the 3-3 bar to include also the first premolars (43-34 retainer) is useful. This is done simply by adding and bonding a small piece of thin wire between the premolar and canine (Figures 14-50 and 14-51). The 43-34 design also may be used when after orthodontic leveling of the six anterior mandibular teeth the orthodontist desires to prevent their reerupting above the functional occlusal plane. Some companies supply preformed lingual 3-3 retainers with bonding pads. These may be more difficult to fit and bond tightly. At the same time, obtaining maximal contact on the lingual surfaces of all four incisors also may be more difficult.

Failure analysis Initial failures with first-generation bonded lingual 3-3 retainers were classified into two types.252 Type I failure

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Figure 14-50 A, A 43-34 retainer can be used when the first premolars are blocked out labially or tipped mesially pretreatment. B, The 0.030-inch 3-3 retainer bar is extended by means of a thin (0.0215-inch coaxial) goldcoated wire between the canine and first premolar.

B

A

Figure 14-51 A, Adult patient with pretreatment blocked-out right second and left first premolar treated with extraction of the second premolar on the right side. B, Final result is retained by means of a short labial gold-coated retainer in the closed extraction site and a 3-34 retainer.

was related to separation at the tooth-adhesive interface and occurred with the highest frequency. Type I failure most commonly resulted from moisture contamination or movement of the lingual bar during the initial polymerization of the composite. Type II failure occurred at the adhesive–retainer wire interface and resulted from inadequate bulk of adhesive for sufficient strength (or abrasive wear of the adhesive). An important note is that with adequate technique, one can avoid both types of failure. In other words, a clinician who experiences discouraging failure rates should reevaluate and improve the technique of making bonded lingual retainers.

Lingual retainer adhesives Different composite resins have been advocated for bonding retainer wires.26 Unlike the adhesive under a bracket,

the lingual retainer resins remain exposed to the oral cavity and therefore require some specific physical properties. Several specific lingual retainer adhesives may offer ease of application, optimal handling, improved patient comfort, and minimal abrasive wear. Recent findings228 indicate that light-activated composites may have these properties. The amount of total light energy delivered to the composite resin determines hardness,21,81,187 wear resistance,82 water absorption,171 residual monomer171 and its biocompatibility.57 Recent studies have tested the surface hardness228 and conversion rate230 of some different lingual retainer adhesives. Two light-cured adhesives (Transbond LR, 3M/Unitek; and Light Cure Retainer, Reliance Orthodontics) were cured with conventional halogen (Ortholux XT), fast halogen (Optilux 501), and plasma arc (PowerPac, American Dental Technologies,

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Corpus Christi, Texas) light sources and were compared with autopolymerizing diluted or undiluted Concise resin.70 The following conclusions emerged: 1. Plasma arc and fast halogen lights are quicker alternatives than conventional halogen lights without compromising final hardness values of the lingual retainer adhesives. 2. Some adhesives may need unexpectedly long curing times with fast curing lights (Light Cure Retainer with PowerPac in this study). 3. Transbond LR yielded significantly higher surface hardness than Concise and Light Cure Retainer, with Concise being significantly harder than Light Cure Retainer. 4. The dilution of Concise resin decreased the in vitro surface hardness, which in turn may decrease its clinical abrasion resistance and longevity. The authors’ ongoing clinical study on lingual retainers bonded with a split-mouth design using Transbond LR on one side and diluted Concise on the other so far has demonstrated equal and excellent success rates. After 2 years, only one bond failure occurred in the Concise group. The heat caused by rapid curing with high-intensity lights160 and shrinkage of the composite resin138 probably are of little clinical concern for the small amount of resin used when bonding lingual retainers.

Bonding 3-3 retainer bar with chemically cured composite resin The following clinical recommendations (Figure 14-52) represent the authors’ present approach. The basic principles have been tested clinically over several years. Although it may seem possible to take shortcuts, this is strongly discouraged; strict adherence to a meticulous technique has been found to be the key to long-term success. The clinical procedure with a two-paste chemically cured composite resin is as follows: 1. While the orthodontic appliances remain in place, take a snap impression of the patient’s teeth and pour a working model of hard stone (plaster is inadequate because it may abrade during wire fabrication, and then the retainer will not fit in the mouth). 2. Using the working model as a guide, bend a plain round stainless steel or gold-coated wire of 0.030- to 0.032-inch diameter with a fine, straight three-jaw or similar pliers so that the wire precisely contacts the lingual surface of all mandibular incisors (see Figure 14-52, A and B). 3. Sandblast the ends with 50-µm aluminum oxide powder for about 5 seconds from different directions, using the Microetcher (see Figure 14-52, B) in a dust cabinet. 4. Clean the lingual surfaces of both canines with a tungsten carbide bur (#7006). 5. Check the position of the wire in the mouth. When optimal, fix with three or four steel ligatures around

6.

7.

8.

9.

10.

11.

the bracket wings of the incisors (see Figure 14-52, C and D). The high lingual saliva evacuator–bite block–tongue holder provides a dry working field with good overview (see Fig 14-52, C). One to three cotton rolls can be placed in the labial lower incisor region (but the lip expander is not used). With retainer wire in place, etch the lingual surfaces of the canines with colored phosphoric acid gel (Ultraetch 35% or Etch-Rite 38% [Pulpdent];) (see Figure 14-52, E) for 30 seconds. Rinse and dry completely. Use a high-speed vacuum evacuator. Sealant is not needed on lingual surfaces, partly because of the reduced risk of decalcification. This fast and efficient procedure reduces the risk of moisture contamination. Bond the retainer using a two-step procedure: a. Tacking: Tack the wire to both canines with a small amount of a flowable light-cured composite resin (e.g., Revolution, Kerr) and cure for 5 seconds (see Figure 14-52, G). This initial tacking is vital for strength. Because the wire now cannot be displaced, the bulk of adhesive can be added with a totally undisturbed setting. b. Bulk of adhesive: Bond the retainer wire to the right and left canines, applying resin from the gingival margin to the incisal edge with a composite-placement instrument.257 Check with a mouth mirror to see that enough adhesive is used, and add more composite resin wherever required (often in the mesiogingival and distogingival corners). Having enough adhesive in the mesiodistal and incisogingival directions is important (see Figure 14-52). Trim along the gingival margin and contour the bulk with an oval tungsten carbide bur (#7408; see Figure 14-52, I) so that it has a smooth contour in an incisogingival direction. Use a smaller bur (#2) interdentally. Instruct the patient in proper oral hygiene and use of dental floss or Superfloss (Oral-B, South Boston, Massachusetts) beneath the retainer wire and along the mesial contact areas of both canines (Figure 14-53). Instruct patients to floss once daily to prevent accumulation of calculus and plaque.

Bonding 3-3 retainer bar with light-cured composite resin When using a light-cured composite resin (i.e., Transbond LR), the previous steps 1 to 7 are identical. The procedure continues as follows: 8. Following the rinse and drying, use a fine brush and apply a thin coat of moisture insensitive primer (Transbond MIP) on the sandblasted ends of the retainer wire and on the etched enamel. This will reduce the risk of moisture contamination.

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F

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H

Figure 14-52 Making the bonded 3-3 retainer bar. A, Careful adaptation of retainer wire on stone model using fine threejaw pliers. B, Sandblasting terminal ends of retainer bar. C, Lingual saliva ejector with high bite block (3M/Unitek) secures an optimally dry working field with no interfacing appliances. D, The 0.030-inch goldcoated wire is positioned by means of three steel ligatures. E, Ultraetch 35% phosphoric acid gel for acid etching. F, Treated area clearly indicated. G, Initial tacking with small amount of flowable light-cured composite resin. H, Bulk of adhesive added to tacked retainer. Continued

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I

J

Figure 14-52, cont’d I, Trimming adhesive with #7408 tungsten carbide bur. J, Final appearance.

A

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Figure 14-53 Interdental cleaning under a bonded 3-3 retainer. A, If a floss threader is not available, a loop is formed over two incisors and moved under the retainer bar. B, When one end of the floss is pulled in, the other will snap free and can be grabbed with the fingers. Patients are instructed to move the floss over the interproximal surfaces once daily.

9. Using the adhesive dispensing barrel and capsules, apply the Transbond LR adhesive to the right and left canines. Shape the resin bulk with fine brush strokes from the gingival margin to the incisal edge. A small amount of Transbond MIP on the brush tip will dilute the composite resin and make it flowable, and this will create a smooth, gentle contour in an incisogingival direction. It takes some experience to find the right consistency. If too much primer is added, the adhesive will drift away from where it is placed and may flow interdentally and contact the gingiva. Optionally, the adhesive may be transferred from a mixing pad. The adhesive on the mixing pad should have a light-impermeable cover. 10. Same as the previous step 9. 11. Light cure the composite resin according to instructions for light source used (e.g., 5 seconds

with the plasma arc light or 40 seconds with conventional halogen light). Cut the ligature wires. 13. Same as the previous steps 10 (trim whenever necessary) and 11.

Long-term experience Experience with bonded 3-3 retainer bars over 10 to 15 years is generally excellent, provided careful bonding technique is used.17,26,253,254,257 Particularly, the third-generation 3-3 retainer is a fine mandibular retainer. Not only is the retainer solid, easy to place, and hygienic, but also it appears to be safer than mandibular retainers in which all six anterior teeth are bonded, which is equally important. A patient notices immediately whether a retainer comes loose when it is bonded only to the canines. The patient then can call for a rebonding appointment to remove the retainer if necessary. For several years, a mandibular bar

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TABLE 14-1

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Hierarchy of Success Rate for Different Types of Bonded Lingual Retainer

Type of Retainer

Wire Diameter

Mandibular 3-3 Mandibular 321-123 Maxillary 21+12 Maxillary 321+123

0.030 inch 0.0215 inch 0.0215 inch 0.0215 inch

Number of Patients

Success Rate (No Loosening or Wire Breakage)

381 191 323 186

96.5% 94.7% 93.8% 78.5%

Data refer to gold-coated retainers bonded from May 1994 to May 2004. Mean observation time is 4.2 years (range 1 to 10 years). Success rate refers to intact retainers (without bond failure or wire fracture) throughout the follow-up period. All retainers were bonded in the same office by one orthodontist (B Zachrisson).

bonded only to the canines has been the authors’ preferred retention method in adolescent and many adult patients. However, occasional cases of slight relapse anteriorly may occur when using retainers bonded only to the canines.17 For this reason, an flexible spiral wire (FSW) retainer bonded to all six anterior teeth (see the following discussion) may be indicated for adult patients with considerable pretreatment crowding. The senior author’s long-term (up to 7 years) experience with third-generation stainless steel and gold-coated 3-3 retainer bars show excellent outcomes with few loosenings (Table 14-1). The failure rates are considerably lower than those reported by others,16,26 which probably is explained by careful bonding procedure (see Figure 14-52). Some initial problems with corrosion caused by microleakage around the gold-plating have made it advisable to extend the sandblasting slightly beyond the area of composite bonding (see Figures 14-50 to 14-52).259 Many patients apparently have difficulties keeping the retainer area really clean, despite patient instruction in hygiene. Accumulations of supragingival calculus and stain often are noted along and beneath the retaining wire,106 whereas decalcification and caries are observed only exceptionally.17,26,97 Clinical data indicate no significant difference in plaque and calculus accumulation between round and spiral retainer wires.11,16,17 However, the presence of even large amounts of calculus around mandibular retainers is not alarming in young, healthy patients with no periodontal pockets.89,238 Gaare et al.89 compared the effect of toothbrushing after professional prophylaxis in patients with large amounts of calculus (removal requiring an average time of 1 hour per patient) with the effect of toothbrushing as the sole hygiene method. The authors found no significant benefit of the calculus removal, which supports the hypothesis that it is not the calculus but the plaque that forms on it that has pathogenic potential. The effects of calculus accumulations on retainers in adults with existing periodontal problems are unknown at present.238

Because the retainers are invisible, a problem may exist in deciding when to remove them. Extended retention periods (up to 10 years) now are recommended by most clinicians.30,98,190,259 For adolescent patients, Behrents30 recommended retention into the mid-20s for males and until the early 20s for females. The long retention periods are favorable in many patients while waiting for the patient’s third molars to erupt259; long retention counters the effects of postpubertal growth activity and maxillomandibular adjustments,30 which may continue well into the second decade and longer.30,259 As an alternative, the bonded retainer may be replaced after several years with a removable one for long-term or permanent nighttime wear.

Direct Contact Splinting In the late 1970s several preliminary and short-term clinical reports were published on direct contact splinting of segments of teeth. The reports appeared mostly in the orthodontic and periodontic literature and represented attempts to prevent postorthodontic space reopening between teeth and provide stability against traumatic jiggling (so-called periodontal splints). A variety of techniques and adhesive resins were used.186 Although some degree of clinical success was experienced, follow-up results indicated a high percentage of bond breakage.14,186,210,250 Bond breakage was illustrated clearly in some experiments on postorthodontic splinting (Figure 14-54). Careful technique involved the use of rubber dams for moisture control, toothpicks to avoid interdental flow of adhesive, and bonding adhesive applied in a wide incisogingival area. A number of clinical situations calling for specific retention were addressed, using two different restorative-type composite resins and one lightpolymerized sealant.250 The results were consistently discouraging; breakage or fracture of the adhesive occurred within a few weeks or months whenever segments larger than two teeth were splinted.

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Figure 14-54 Direct contact splinting. A, Working field with rubber dam, toothpicks, dental floss, and clamp. B, Contact splint using light-cured sealant. Note the wide contact area in the apicoincisal direction. C, Break after 2 months of splinting. D, Breaks in mandibular canine-to-canine splint where composite resin was used. Dental floss is inserted to show location of the failures. Note that the splint broke into segments of one or two teeth.

These results are in clear contrast to the authors’ experience with the FSW retainers. The apparent reason for the bond breakage is the need for independent physiologic tooth movement during function. Unfortunately, the rigidity of the contact splints does not facilitate individual tooth movements and therefore is not recommended as a mode of bonded retention. Based on the foregoing and other studies, one generally can state that contact splinting without some form of wire reinforcement should not be considered a method of choice. When contact splinting on pontics is used for missing maxillary lateral incisors or to hide empty spaces after extractions of premolars or lower incisors in adults, reinforcement of the splint with a small piece of braided wire is recommended (Figures 14-55 to 14-57). If the splint breaks, the wire will keep the pontic in position.

Flexible Spiral Wire Retainers Clinical experience and differential retention philosophy have demonstrated the need for two types of bonded

wire retainer: 1. Thick wire (0.030- or 0.032-inch diameter) 2. Thin wire (0.0215-inch diameter) The thick wire is used for the mandibular 3-3 retainer bar bonded on the terminal dental units only, whereas the thin spiral wire is used for various retainers in which all teeth in a segment are bonded. In discussing the FSW retainer, the following subdivisions are used: 1. Advantages and disadvantages 2. Long-term experience 3. Technical procedure 4. Repair 5. Indications 6. Conclusions and clinical recommendations In 1977 the authors’ results indicated that bonded retainers using thin multistrand flexible wire (0.015to 0.020-inch diameter) appeared to be suitable for preventing space reopening in different clinical situations.252 Long-term (up to 15 or more years) results are now available for different wire types (see Table 14-1), verifying that the combination of thin spiral wire

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Figure 14-55 A, Missing lateral incisor case where an acrylic pontic was direct splinted to the central incisor during the orthodontic treatment. B, Note braided rectangular wire reinforcement.

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Figure 14-56 A, Direct contact splinting of extracted mandibular left central incisor in an adult woman (B), where the protruding lower incisors had caused multiple spacing of maxillary incisors.

with wear-resistant bonded composite can provide a useful mode of retention for a variety of postorthodontic situations70,253,254,255,258 (Figure 14-58).

Advantages and disadvantages Flexible spiral wire retainers have several advantages: 1. They may allow safe retention of treatment results when proper retention is difficult or even impossible with traditional removable appliances.

2. They allow slight movement of all bonded teeth and segments of teeth. Apparently this is the main reason for the excellent long-term results. 3. They are invisible. 4. They are neat and clean. 5. They can be placed out of occlusion in most instances. If not, the possibility remains of hiding the wire under a slight groove in the enamel.

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Figure 14-57 A, Direct contact splinting of acrylic pontic to hide the premolar extraction spaces in an adult male patient concerned not to show empty spaces. B, Both contact splints were reinforced with a braided rectangular wire, which kept the pontics in place during the canine retraction period despite resin fracture in both contact points. The pontics were ground on the distal surfaces to accommodate to the space conditions.

6. They can be used alone or with removable retainers. However, FSW retainers have some disadvantages. Good oral hygiene of patients is mandatory. Daily flossing in each interdental space is recommended with the use of a dental floss threader or Superfloss gingival to the wire. The gingival reaction of course also depends on careful removal of excess adhesive at the time of retainer bonding.254 Side effects in the form of undesirable movement of bonded teeth may occur if the wire is too thin or not entirely passive while bonding.18,70 Finally, FSW retainers are more subject to mechanical stress and are thus less indicated in deep overbite cases when the wire cannot be placed out of occlusion.19

Long-term experience Experiments in the late 1970s and early 1980s used different sizes (0.015- to 0.020-inch diameter) and types of multistranded wires.252,254,256 Early findings included the following: 1. The incidence of wire breakage appeared to decrease with increasing wire diameter.

2. Undesirable side effects and tooth movements occurred when short segments of 0.015-inch wire were used. 3. An unacceptable incidence of bond failures occurred when the wires were bonded to the lingual surfaces of premolars.251,252,256 Bond failures and other clinical features of lingually bonded retainers were reported in 1991 by Dahl and Zachrisson.70 The observation periods were then an average of 6 years for maxillary and mandibular 0.0215-inch three-stranded wire* and 3 years for the same diameter five-stranded wire. The failure rates were considerably lower than those reported in other recent studies of lingual retainers over periods of 2 to 3 years.17,19,26 The results with the fivestranded Penta-One wire (Masel Orthodontics, Bristol, Pennsylvania) were particularly encouraging. The failure rates for loosening were 8% in the maxilla and 6% in the mandible; for wire fracture the failure rates

*Tri-Flex wire (Rocky Mountain Orthodontics, Denver, Colorado) and Wildcat wire (GAC International).

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Figure 14-58 Four different clinical situations in which a lingual flexible spiral wire retainer is used for improved retention. The cases represent significant midline diastema of maxillary central incisors (A and B), bilaterally missing maxillary lateral incisors (C and D), one lower incisor extraction in Class III plus open-bite tendency case (E and F), and two palatally impacted maxillary canines (G and H). In D the six-unit retainer is bonded in the occlusal fossa of the first premolars, whereas in H a short labial retainer is used bilaterally to stabilize the mesially rotated and palatally displaced canines and the distally rotated first premolars.

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were 3% in the maxilla and were nonexistent in the mandible.70 Since May 1994 the senior author has used a goldplated version (Gold’n Braces) of the five-stranded Penta-One wire exclusively and has observed few failures (see Table 14-1). The mechanical properties of the stainless steel and gold-coated wires are identical, but the latter is preferred because it is (1) more elegant and (2) gives less darkening shine-through effect on transparent incisors. The discrepancies between the authors’ experience and that of other studies probably can be explained by fewer occlusal interferences (with less contact with opposing teeth to allow for more wear) and by technical factors (such as adequate buccolingual width of composite over the wire, smooth contouring of the adhesive, completely undisturbed setting of the adhesive in every case, and careful adaptation of the wire to the lingual contours of the teeth). The reduction of wire breakage compared with earlier results is related to the increased flexibility of five smaller wires occupying the same diameter as the three larger wires in previous retainers. Because a common mode of failure with bonded FSW retainers is abrasion of composite and subsequent loosening of bonds between wire and composite,19 one is advised to avoid occlusal contact or to add a thick layer of adhesive over the wire. Even in the absence of tooth contact, such as in the mandible, mechanical forces (tongue activity, toothbrushing) may cause notable abrasion over the years. Patient acceptance of the FSW retainer is excellent.23,70 In addition, adults especially appreciate that the stability of the treatment result does not depend on their cooperation, which is the case when removable retainers are worn continuously or are worn at night. When patients with previous multiple spacing of anterior teeth were in the retention phase of treatment, it often was found that after about 6 months small spaces (1 to 2 mm) opened distal to the terminal ends of the retainer wire. Because these spaces apparently did not open further, it was concluded that they illustrated a settled occlusion with the FSW retainer in place in a new state of physiologic equilibrium.23,70,252 Depending on the occlusion and the patient’s dental awareness, such spaces could be filled with mesiodistally extended fillings or crowns or could be allowed to remain. At present, little is known about the length of time that the bonded FSW retainer should be left in place. The type of original malocclusion and the patient’s age and ability to keep the retainer clean may be decisive factors. As long as the retainer is intact, the treatment result is maintained; and as long as the patient performs adequate plaque control, no real reason exists to remove the retainer.

Accumulations of calculus in mandibular FSW retainers may not be alarming.17,89,231 In selected cases retainers may be used for permanent stabilization (see Chapter 27). Advanced periodontal cases probably also need permanent retention (see Figure 14-59). Further follow-up research is needed for semipermanent and permanent use of bonded retainers. As discussed for the 3-3 retainers, in some cases it may be practical to use the bonded lingual retainer for a prolonged retention period and then to replace it with a removable retainer for nighttime wear on a more permanent basis.

Bonding flexible spiral wire retainer with chemically cured composite resin Based on clinical experience with the FSW retainer over the past 20 years, the following clinical direct-bonding procedure is advocated for its fabrication and bonding70 (Figure 14-60): 1. Toward the end of orthodontic treatment, take a snap impression and pour a working model in stone. 2. Using fine, three-pronged wire-bending pliers and marking pen, adapt the 0.0215-inch Penta-One steel or gold-coated wire (Gold’n Braces) closely and passively to the crucial areas of the lingual surface of the teeth to be bonded. Cut the wire to the required length. 3. When making a maxillary retainer, tilt the patient into a horizontal position to allow direct view and facilitate working on the lingual aspects of the incisors (Figure 14-61). 4. Check the retainer wire in the mouth for good fit in an entirely passive state and adjust if necessary. 5. Clean the surfaces to be bonded with a tungsten carbide bur180,257 and etch with phosphoric acid gel (Ultraetch or Etch-Rite) (Figure 14-62; see also Figure 14-60) for 30 seconds. 6. Use a four-handed approach (or similar) for initial tacking (see Figure 14-60, C, and 14-63, B). Hold the wire by hand in the optimal position while tacking it to one incisor with a small amount of flowable light-cured composite resin (e.g., Revolution). Check the wire for passive tension after tacking (see Figure 14-62, E). If the wire is passive, tack the remaining teeth; if not, remove the wire and start over. 7. The initial tacking (see Figure 14-60, E) is vital to securing wire passiveness and optimal bond strength because the tacked wire cannot be displaced and cause disturbed setting when the bulk of adhesive is added. Check with a mouth mirror to be sure that enough adhesive is used. Add more adhesive whenever it is required. That the adhesive cover a large buccolingual area over the wire is important for strength.

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Figure 14-59 Adult female patient with advanced hard and soft periodontal tissue destruction and pathologic migration of the maxillary anterior teeth before (A to E), during (F), and after (G to J) orthodontic treatment. The improved dental result is retained by means of six-unit bonded lingual retainers in both dental arches (H and I). Some interdental gingival recession was unavoidable in the maxillary anterior region, but it does not show much clinically (J). The radiographs after treatment showed no progression of periodontal tissue destruction compared with the initial films (C). Continued

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Figure 14-59, cont’d For legend see p. 633.

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Figure 14-60 Fabrication of four-unit flexible spiral wire retainer with chemically cured composite resin. A gold-coated Penta-One wire is adapted carefully on a model with fine three-jaw pliers to fit the lingual contours of the incisors passively. A and B, Acid etching of the lingual surfaces of the upper incisors. C and D, The initial tacking to one incisor is made with flowable light-cured resin, with the wire held in the optimal position by a finger. This initial tacking to one tooth allows direct checking of position and fit of the retainer wire and is the key to avoid unwanted tooth movement as a side effect during the retention period. When correct and passive, the remaining teeth are tacked next with a small amount of light-cured flowable resin (E) before the bulk of adhesive is added in a gingival-occlusal movement (F). Continued

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Figure 14-60, cont’d A thin mix of composite resin then is added with an explorer to fill in the bond mesially and distally on each tooth. Trimming is made with tungsten carbide burs (G to I). The #7006 bur is ideal incisal to the wire to avoid occlusal interference, whereas the contour gingival to the wire is made with the #7408 bur. J shows the final result.

8. Contour the bulk of adhesive and remove any excess along the gingival margin. Use oval tungsten carbide burs (#7006 and #7408) to obtain correct amount and contour of adhesive (see Figure 14-60, G and H), and remove adhesive interdentally with small, round burs (#1 and #2; see Figure 14-60, I) 9. Instruct the patient in proper oral hygiene and use of dental floss and in each interdental area with a floss threader or Superfloss.

Bonding flexible spiral wire retainer with light-cured composite resin When using a light-cured composite resin (e.g., Transbond LR), follow the foregoing procedure for steps 1 to 5 (see Figures 14-62 and 14-63). The procedure continues as follows: 6. Use a four-handed approach (or similar) for the initial tacking. Hold the wire by hand in the optimal position while tacking it to one incisor with a small amount of Transbond LR

(see Figure 14-62, B). Check the wire for passive tension after tacking. If the wire is passive, add more adhesive and light cure the remaining teeth; if it is not, remove the wire and start over again. 7. Contour the bulk of adhesive with the brush dipped into the primer (Figure 14-61, D). Optionally, transfer the adhesive from a mixing pad, which should have a light-impermeable cover. That the adhesive cover a large labiolingual area over the wire is important for the strength and wear resistance. Trim with burs when necessary. 8. Same as the previous step 9.

Indirect bonding of flexible spiral wire retainer The fixed lingual retainer also can be fabricated with an indirect technique as described elsewhere.24,28,125 A practical approach for lingual retainers is to use indirect bonding with a 2-mm thick polyethylene thermoplastic transfer tray and Transbond LR and Sondhi Rapid Set as adhesive resins.125

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Figure 14-61 A, Working position when making a bonded retainer in the maxilla. B, Tacking. C, Adding composite resin. D, Trimming.

Repair

Indications

The most common problem following wire fracture or the loosening of the bonding site(s) in FSW retainers is unwanted movement of one or more teeth. At this stage, the teeth are not seated firmly in their sockets and therefore generally can be forced back into position using techniques such as heavy pull with one or two steel ligatures (Figure 14-64, A and B). When the repair is made, a temporary contact \splint using composite resin or a temporary bonded labial wire have proved to be of considerable value. The latter normally provides better stability and allows a good working area with undisturbed setting of the repair adhesive (Figure 14-64, C and D). After the repair the temporary labial wire (or contact splint) is removed with tungsten carbide burs.

At least two indications or suggestions are useful for using bonded FSW retainers: 1. Prevention of space reopening a. Median diastemas b. Spaced anterior teeth c. Adult periodontal conditions with the potential for postorthodontic tooth migration d. Accidental loss of maxillary incisors requiring the closure and retention of large anterior spaces e. Mandibular incisor extractions 2. Holding of individual teeth a. Severely rotated maxillary incisors b. Palatally impacted canines In these and other situations the bonded thin spiral wire retainer can be used alone or with a removable

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Figure 14-62 Instruments (A) and method (B to G) for fabrication of six-unit lingual flexible spiral wire retainer with lightcured composite resin. After an 0.0215-inch stainless steel or gold-coated Penta-One wire is adapted for optimal fit on the lingual surfaces of all teeth (B), the teeth are acid etched with phosphoric acid gel (C). Composite resin is added to one incisor (D and E) and light cured. After a check that the wire is passive and has a good fit to the remaining teeth, composite resin is added, shaped with the aid of liquid resin and fine brush (F), and is light cured (G). H shows the final result.

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Figure 14-63 Fabrication of four-unit flexible spiral wire retainer with light-cured composite resin. A, Etching with phosphoric acid. B, Finger-holding of wire while tacking one incisor. C, Light curing the remaining teeth. D, Final result. See text for details.

retainer. Some details of specific interest relative to the retention in this list of treated malocclusions are discussed briefly. Closed Median Diastemas. The bonded FSW retainer is ideal for short- or long-term retention of closed median diastemas. The 0.0215-inch five-stranded wire should be bonded preferably over four units (Figures 14-65 and 14-66) to reduce the risk of untoward side effects.70,254 Multiple Spacing of Anterior Teeth. Unimaxillary or bimaxillary spacing of teeth in adolescents and adults is generally easy to treat but difficult to retain. The tendency for space reopening may be great, even despite long periods of retention with conventional appliances. For this reason, a number of experimental approaches have been reported recently, including the use of splints,76 staples,60,63 and mesh.93,186

None of these methods seems to have gained a wide acceptance, however. Although good conditions for adequate plaque removal are definitely necessary in any type of dental replacement therapy, this principle does not seem to have been adhered to in several of the suggested bonded splinting appliances. Compared with the neat FSW retainer, the splinting appliances may appear unnecessarily bulky and complicated. As discussed70,254,256 and illustrated (see Figures 14-58 and 14-59), the bonded FSW retainer is preferrable.

Periodontal Conditions with Tooth Migration. The bonded FSW retainer is well suited for stabilizing and maintaining teeth into their new position after orthodontic treatment of adults with periodontal problems256,261 (see Figure 14-59). The main advantage over removable retainers worn part time is that jiggling is avoided. The FSW also may be used for periodontal

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Figure 14-64 Repair of broken retainer (fatigue fracture of wire between left central and lateral incisor), using labial temporary wire for stabilization during rebonding. When the loose teeth have been pulled together with steel ligatures (A and B) to close a small space, the temporary wire is bonded labially with adhesive after a 5-second etch. After setting, the steel ligatures can be removed to provide a nice working field (C), where the repair wire can be bonded with no disturbed setting gingival to the main retainer wire (D).

splinting when teeth exhibit increased mobility or when the mobility is of a magnitude that disturbs masticatory function or patient comfort.96 Recently, extracoronal splinting using acid etching and composite resins has been suggested, alone or incorporating ligature wire, a perforated cast form, fiberthread or fiberglass,169 or grid material.186 Direct contact splinting is not durable enough; composite over wire ligation creates unnecessary bulk and compromises esthetics; and the cast splints require expensive and time-consuming techniques. Rosenberg186 reported that the use of orthodontic grid-material splints is a completely reversible procedure. The splints are easy to construct and are inexpensive, and they require minimal chairside time. However, all these advantages are also present in the bonded FSW retainer, which in addition has a considerably neater and more hygienic appearance.261 To reduce failures in terms of wire fracture (Figure 14-67) or loosening, it is important that the patient try to avoid biting on a bonded maxillary retainer.

In some instances, a deep overbite will result only in abrasive wear of the composite and wire without loosening. However, several studies indicate that direct biting on the retainer wire is the most common reason for retainers coming loose.19 Following abrasion of the adhesive, loosening occurs between composite and the wire. Thus in cases of deep overbite, bonding the retainer wire gingivally to the contact line (Figure 14-68) or, if this is not possible, hiding the wire in a small groove in the enamel is recommended. Accidental loss of Maxillary Incisor(s). Most accidents in which maxillary central incisors are knocked out of the mouth occur in the age period from 8 to 10 years.9 When orthodontic space closure is selected as the treatment alternative (a discussion on indications is presented elsewhere68,209,253), the canines and premolars frequently have not yet erupted, and a two-stage orthodontic treatment is indicated. In the first stage the lateral incisors are brought mesially to prevent bone

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Figure 14-65 Recommended version of removable plate to be used with a four-unit bonded lingual retainer. The rectangular (0.019 × 0.026 inch) labial wire of this plate extends distal to the lateral incisors and has a soldered extension wire to prevent flaring of the canines. A holding clasp of 0.8-mm round wire is distal to the second molars.

resorption and allow mesially directed eruption of the canines. Then 1 to 3 years must pass until all permanent teeth have erupted, at which time the second stage of orthodontics can be performed. When removable retainers are used in the waiting period between the two stages, more often than not the patient perceives the experience as a prolonged and tiring orthodontic treatment over too many years. The FSW retainer is excellent in these situations. When the FSW retainer is bonded to the lingual surfaces of the approximated lateral incisors, the patient soon forgets about its existence, and consequently the patient is fresh and cooperative when the final stage of orthodontics begins. Of course, a similar approach can be chosen in other two-stage operations. Mandibular Incisor Extractions. As discussed by Joondeph (see Chapter 27), Tuverson,227 and others78, sometimes one or two lower incisors are extracted as part of orthodontic treatment. This may be true in some adult patients and in patients with an open-bite Class III tendency or a periodontal problem involving excessive gingival recession on the most protruding incisor. Whatever the reason for the extraction, clinical experience indicates a high risk for space

reopening with conventional retainers, whether removable plates or fixed 3-3 retainers. By contrast, an FSW retainer bonded to the three remaining incisors (or extended farther distally; see Figure 14-58, F) safely maintains the treatment results for as long as it is kept in place. Rotation of Maxillary Incisors. A well-known clinical problem is that severely rotated maxillary incisors in different types of malocclusion have a great tendency to relapse. This is particularly undesirable because the upper anterior region is the most esthetically important one for the patient. Several techniques can be used to improve the stability, including overrotation, fiberotomy, and extended retention periods. Still another aid may be the placement of a bonded FSW retainer. Whenever a removable plate is used in the maxilla together with a bonded six-unit retainer, the version shown in Figure 14-69 is recommended. 21-12 Retainer. The FSW retainer also can be bonded to the four mandibular incisors as an alternative to a bonded 3-3 retainer. The indications are primarily when the operator is uncertain of the optimal

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Figure 14-66, cont’d For legend see opposite page.

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Figure 14-66 Recommended routine retention for adolescent patients. Young girl with unilateral crossbite (A to C) after orthodontic treatment involving four premolar extraction (D and E). F, After treatment. Retainers include an upper four-unit flexible spiral wire retainer (G), a lower 3-3 bar (H), and a removable plate (see Figure 14-65 for design).

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Figure 14-67 Fatigue fracture of a lingual retainer wire. A, A wire fracture has occurred between the right lateral and central incisors. B, Significant abrasive wear of a bonded lingual retainer in the maxillary left canine area caused by occlusal contact with the mandibular canine. The round wire has been worn flat. When a state of equilibrium is reached, such retainers still may be kept in place for several years because of the retentive potential of the wire spirals.

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Figure 14-68 A, If a deep overbite situation remains after treatment, the risk of loosening of a bonded lingual retainer is obvious. B, To avoid occlusal interference, the retainer wire may be bonded gingival to the contact line.

intercanine distance or wants to canines to settle undisturbed for other reasons. However, because the longterm results are excellent for six-unit mandibular retainers,70 little reason exists to use the four-unit solution.128 Palatally Impacted Canines. Canines that have erupted into the palate also may display great relapse tendency in a lingual direction, particularly when no interlocking lateral overbite is present. In such instances an FSW retainer bonded to the lingual or buccal of the teeth has proved to be an excellent retainer

(see Figure 14-58, G and H). The main advantage of the FSW retainer is that it allows more undisturbed bone and soft tissue healing over long periods than can be obtained with removable retainers.

Conclusion and clinical recommendations When it comes to finding simple, reliable, and neat retainers and splints for a variety of clinical situations, the bonded FSW retainer opens up a range of new possibilities. The one limitation to its design and use in difficult or unusual circumstances is the imagination

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Figure 14-69 A and C, Recommended version of removable plate to be used with a six-unit bonded lingual retainer. The labial wire of this plate extends distal to the bonded retainer to avoid the risk of retainer wire fracture. The acrylic of the plate can be ground away from the teeth involved in the bonded retainer, B and D.

and alertness of the operator. Clinical experience with the FSW retainer over the past 20 years has been excellent when meticulous technique was used62,223; otherwise, results can be discouraging. Because the failure rates increase significantly when the canines (and first premolars) are included in a maxillary FSW retainer (see Table 14-1), use of a fourunit design combined with a removable plate (see Figures 14-65 and 14-66) rather than a six-unit bonded retainer (Figure 14-70, see also Figure 14-69) is safer for routine retention in children and adults. The 3-3 bar and the 321-123 retainer show excellent and similar success rates (see Table 14-1). The 3-3 bar is a safe retainer, and this design may be recommended for most children. For adults and adolescent patients with pretreatment spacings and similar malocclusions, the bonding of all six anterior teeth may be preferable.

Direct-Bonded Labial Retainers Clinical experimentation with short labial retainers was started in the late 1980s to try to improve the long-term results in some specific retention situations. Typical

problems were the following: 1. Inability to prevent some space reopening in closed extraction sites in adults 2. A tendency for some lingual relapse of previously palatally impacted canines 3. Space reopening when molars and premolars had been moved mesially in cases with excess space Common to these situations was that some support in the premolar area for 1 to 2 years appears advantageous to improve stability. The background for bonding retainer wires labially was based on unsatisfactory results when the orthodontist bonded wires to the lingual surface of premolars.254,256,259 The alternative—bonding the wire occlusally in the premolars—presents other problems. In most instances antagonistic contact cannot be avoided unless a groove is prepared, which is probably not acceptable in routine situations. It was decided therefore to bond short retainer wires labially to examine success rates and patient reactions.

Technical procedure In principle the fabrication of labial retainers is similar to the technique used for direct bonding of lingual retainers.

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Figure 14-70 Combination of six-unit bonded lingual retainer and simplified Crozat appliance for retention in adult female patient with an anteriorly constricted maxillary dental arch and rotated and blocked out lateral incisors and canines (A to C). E, The Crozat is optimal for long-term retention of crossbites in adults. If the appliance is not worn for some time and slight transverse relapse occurs, its flexibility allows for recovery (similar to a spring retainer), in contrast to what is possible with a conventional removable plate. Note improvement of smile fullness (F) compared with the start (A).

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1. A straight piece of 0.0215-inch Penta-One wire (gold-coated or stainless steel) is cut to the desired length. 2. After etching, the retainer wire is tacked on the teeth. 3. After the adhesive sets, a bulk of adhesive is added. 4. Contour trimming of excess is done with tungsten carbide burs (#7408 and #7006) and interdental trimming is done with small round burs (#1 or #2). Care is taken to avoid contact between composite and gingival margin at the bonding sites, as well as contact between the interdental papillae and the retainer wire.

Long-term results The first follow-up study of direct-bonded labial retainers as reported by Axelsson and Zachrisson23 demonstrated excellent results for short segments (two teeth) regarding bond success rate and, surprisingly, for patient acceptance. A gold-coated labial wire (see Figure 14-51, B) is understandably more acceptable than a steel wire, even if some of the plating may wear off over time. The failure rates for retainers of two teeth were about 4% over an average period of 2 years. The retainers were placed over closed extraction sites in adults (Figures 14-71 to 14-73) or for added retention of previously palatally impacted canines (see Figure 14-58, H). When longer retainers (three to four teeth) were placed labially in the mandible, however, the bond failures increased significantly.23

OTHER APPLICATIONS OF BONDING Numerous other clinical possibilities of interest to orthodontists exist in which the acid-etch technique

and bonding has proved useful: • Space maintainers • Semipermanent single-tooth replacements • Trauma fixation • Resin buildups for tooth size and shape problems

Bonded Space Maintainers Several approaches to bonded space maintainers have been described,15,170,201 with varying degrees of shortterm success reported. Long-term results on a group of patients are not available for any design. Analogous to the encouraging results with the bonded 3-3 retainers are the findings of Årtun and Marstrander,15 who compared the durability of 64 space maintainers when a round 0.032-inch wire with terminal loops or a twisted stainless steel wire of 0.032-inch diameter without loops was bonded with composite resin (Concise). A utility wire design was used to reduce the influence of occlusal forces. Although the failure rate after 6 months was significantly higher for the first alternative, it was in the 10% range for the second (an acceptable level). The main reason for the difference was thought to be the fact that the spiral wire allowed less bulk (and thus less occlusal interference) and was easier to individualize. Simonsen201 reported bonding space maintainers on the lingual sides of teeth, apparently with good success. Figures 14-74 to 14-76 show more recent designs of bonded space maintainers made from plain, round 0.032-inch stainless steel wire sandblasted terminally for micromechanical retention or from gold-coated 0.030-inch wire. More studies may be needed on specific designs of bonded space maintainers on the labial or lingual aspects before a variant for routine use can be accepted universally.

B

A

Figure 14-71 A, Adult male patient with Class III malocclusion. B, Short labial retainer after extraction of mandibular first premolars.

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D

Figure 14-72 Slight space reopening distal to a short labial retainer in an adult woman requiring upper first premolar extraction. A and B, Gold-coated labial retainers. C, The reopening evidently reflects a tooth size discrepancy that can be addressed when remaking the amalgam fillings. D, The labial wire is inconspicuous on smiling.

Bonded Single-Tooth Replacements Because of the well-known problems with fixed bridgework and removable appliances of the spoon denture type in young patients, acid etching and bonding offer a range of esthetic techniques for the solution of the problem with anterior teeth.184 The use of resin-bonded bridgework (three-unit or cantilever40) has become accepted as a semipermanent procedure. Failure rates over a 10-year period may be in the 30% range,242 particularly if cases are selected to allow no or only limited occlusal contact on the restoration. Higher failure rates have been experienced with the presence of occlusal contact, particularly in children.

A cheaper, simpler, and perhaps more durable alternative than the cast variants for anterior tooth replacement was proposed in 1984 by Årtun and Zachrisson.20 An acrylic prosthetic tooth was used into which were inserted two flexible braided rectangular wires (0.016 × 0.022 inch) and one round (0.0195-inch) spiral wire for support. The procedure aimed at the following properties: 1. Possibility for physiologic movement of the bridge units within the periodontal tissues 2. Avoidance of direct occlusal contact on metal 3. Avoidance of metal shine through 4. Uncomplicated repair

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B

A

D

C

F

E

Figure 14-73 A to C, Young adult female patient with typical Class II, Division 2 malocclusion before treatment. The maxillary first molar was extracted as part of treatment (C). The second molar and first premolar were held together with a short gold-coated labial retainer. The maxillary third molar is erupting. D to F, Note the improved maxillary canine occlusion and incisor torque.

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A

B

Figure 14-74 Recommended design for bonded space maintainers using round 0.032-inch stainless steel wire sandblasted in the terminal ends for micromechanical retentions (A and B) or using six-stranded 0.032-inch spiral wire with utility wire design.

A

B

C

D

Figure 14-75 A and B, Adult man in whom it was necessary to upright the mesially tipped mandibular left second and third molars. C, Gold-coated 0.030-inch space maintainer. D, Before insertion of a single-tooth implant for the absent first molar.

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A

B

C

D

E

F

Figure 14-76 A, Adult female patient with agenesis of two mandibular incisors and thin periodontal tissues. B to D, Goldcoated space maintainer. The mandibular left first and second premolars were moved one tooth width mesially (B) to regenerate improved alveolar bone thickness to accommodate a single implant (E and F).

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Figure 14-77 Three-wire design for single tooth replacement of a missing right lateral incisor (A) and four-wire version of the resin-bonded bridge, where the two braided wires run continuously through the pontic (B). Note the attempts to achieve clean interdental conditions.

5. Access to the pulp cavity and root canal in cases where endodontic treatment might be indicated Clinical results with the three-wire design in a nonselected material without concern for the degree of overbite in 51 adolescents were promising but not entirely satisfactory.20 Bond failure rates were 26% after 2 years and 39% after 3 years. Most breakage occurred on central incisors in direct occlusal contact during protrusive mandibular movements and were seen as wire fracture. The failure rates were much lower when no antagonistic contact with the pontic occurred during functional movements. None of the lateral incisors had come loose (Figure 14-77, A). Later modifications have included an improved fourwire design, using two rectangular braided wires on either side (Figure 14-77, B). In cases in which direct occlusal contact could not be avoided, a small groove was prepared to hide the incisal wire(s). In a nonselected sample of 36 bridges, the failure rate over 4 years with the fourwire design was about 20%.222 Despite these failure rates, this type of replacement has several advantages for use in children and adolescents. Of particular interest is the fact that similar types of replacement can be used during orthodontic treatment. Porcelain or acrylic teeth can be attached to neighbors to avoid empty-looking spaces in adults when premolar or incisor extractions are needed (see Figures 14-55 to 14-57) and for absent maxillary lateral incisors while waiting for a more optimal time for implant insertion.

Splinting of Traumatic Injuries The goal of splinting traumatized teeth is to stabilize, allow healing, and prevent further damage to the pulp and periodontal structures. Several types of traumatic splinting devices are used conventionally,9 but for vari-

ous reasons none of these splints is optimal.186 Thus clinical experiments using different bonded wires are interesting. Short-term studies have demonstrated clinical success with bonded plastic wire and stainless steel spiral wire.9 Such splints allow physiologic mobility of the splinted teeth, which has been found to be preferable to rigid splinting (except possibly for root fractures).

Composite Buildups and Porcelain Laminate Veneers The addition of composite resin or porcelain laminates to noncarious teeth during or after orthodontic treatment may be indicated on single or multiple teeth to solve tooth shape and size problems. A range of situations exist in which buildup techniques may provide esthetic improvement of the orthodontic result. For example, small or peg-shaped maxillary lateral incisors (Figure 14-78) and canines brought into contact with maxillary centrals when the laterals are congenitally missing (Figure 14-79) may need such esthetic improvement.65 Occasionally, autotransplanted first premolars in the lateral incisor position also need the addition of resin. More demanding situations require porcelain laminate veneers or veneer crowns, including cases in which premolars have been autotransplanted to the maxillary anterior region.68,69,209 The esthetic result that may be obtained with one or several porcelain veneers bonded to prepared transplanted premolars is outstanding. The combined surgical-orthodontic-prosthetic interdisciplinary effort is an excellent way to solve difficult treatment problems associated with traumatic injuries of the teeth in young patients.

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B

A

C

D

E

F

Figure 14-78 A and B, Young female patient with agenesis of maxillary right lateral incisor and peg-shaped left maxillary lateral incisor. Clinical result of orthodontic space closure (C) was modified by recontouring the canine to the lateral incisor shape by grinding and making a porcelain laminate veneer on the peg lateral (D and E). E and F show final result.

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Figure 14-79 Composite buildup leading to esthetic improvement postorthodontically for a patient in whom the maxillary lateral incisors were missing. A, After space closure. Note the unfavorable appearance of both canines and the traumatically injured right central incisor (arrows). B, Combination grinding of the canines and composite buildup on the mesial aspects of the canines and the incisal edge of the central incisor. C and D, Results of this quick procedure.

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65. Cook DF, Hilgers JJ: Orthodontic treatment veneers, J Clin Orthod 37:650-655, 2003.

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78. Færøvig E, Zachrisson BU: Effects of mandibular incisor extraction on anterior occlusion in adults with Class III malocclusion and reduced overbite, Am J Orthod Dentofacial Orthop 115:113-124, 1999.

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79. Farquhar RB: Direct bonding comparing a polyacrylic acid and a phosphoric acid technique, Am J Orthod 90:187, 1986. 80. Fejerskov O, Thylstrup A, Joost-Larsen M: Rational use of fluorides in caries prevention: a concept based on possible cariostatic mechanisms, Acta Odontol Scand 39:241, 1981.

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105. Harari D, Shapira-Davis S, Gillis I, et al: Tensile bond strength of ceramic brackets bonded to porcelain facets, Am J Orthod Dentofacial Orthop 123:551-554, 2003.

126. Karamouzos A, Anathoasiou AE, Papadopoulos MA: Clinical characteristics and properties of ceramic brackets: a comprehensive review, Am J Orthod 112:34, 1997.

106. Heier EE, De Smit AA, Wijgaerts IA, et al: Periodontal implications of bonded versus removable retainers, Am J Orthod Dentofacial Orthop 112:607, 1997.

127. Katona TR: A comparison of the stress developed in tension, shear peel, and torsion strength testing of direct bonded orthodontic brackets, Am J Orthod 112:244, 1997.

107. Helvatjoglou-Antoniadi M, Papadogianis Y, Koliniotou-Kubia E, et al: Surface hardness of light-cured and self-cured composite resins, J Prosthet Dent 65:215, 1991.

128. Keim RG, Gottlieb EL, Nelson AH, et al: 2002 JCO study of orthodontic diagnosis and treatment procedures. 1. Results and trends, J Clin Orthod 36:553-568, 2002.

108. Hitmi L, Muller C, Mujajic M, et al: An 18-month clinical study of bond failures with resin-modified glass ionomer cement in orthodontic practice, Am J Orthod Dentofacial Orthop 120:406-415, 2001.

129. Klocke A, Korbmacher HM, Huck LG, et al: Plasma arc curing of ceramic brackets: an evaluation of shear bond strength and debonding characteristics, Am J Orthod Dentofacial Orthop 124:309-315, 2003.

109. Hixson ME, Brantley WA, Pincsak JJ, et al: Changes in bracket slot tolerance following recycling of direct-bond metallic orthodontic appliances, Am J Orthod 81:447, 1982.

130. Klocke A, Shi J, Kahl-Nieke B, et al: Bond strength with custom base indirect bonding technique, Angle Orthod 73:176-180, 2003.

110. Hobson RS, Ledvinka J, Meechan JG: The effect of moisture and blood contamination on bond strength of a new orthodontic bonding material, Am J Orthod Dentofacial Orthop 120:54-57, 2001. 111. Hohoff A, Seifert E, Fillion D, et al: Speech performance in lingual orthodontic patients measured by sonography and auditive analysis, Am J Orthod Dentofacial Orthop 123:146-152, 2003.

131. Klocke A, Shi J, Kahl-Nieke B, et al: In vitro investigation of indirect bonding with a hydrophilic primer, Angle Orthod 73:445-450, 2003. 132. Knierim RW: Invisible lower cuspid to cuspid retainer, Angle Orthod 43:218, 1973. 133. Komori A, Ishikawa H: Evaluation of a resin-reinforced glass ionomer cement for use as an orthodontic bonding agent, Angle Orthod 67:189, 1997.

112. Holt MH, Nanda RS, Duncanson MG: Fracture resistance of ceramic brackets during arch-wire torsion, Am J Orthod 99:287, 1991.

134. Koo BC, Chung CH, Vanarsdall RL: Comparison of the accuracy of bracket placement between direct and indirect bonding techniques, Am J Orthod Dentofacial Orthop 116:346-351, 1999.

113. Hong YH, Lew KK: Quantitative and qualitative assessment of enamel surface following five composite removal methods after bracket debonding, Eur J Orthod 17:121, 1995.

135. Kucher G, Weiland FJ: Goal-oriented positioning of upper second molars using the palatal intrusion technique, Am J Orthod 110:466, 1996.

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136. Kusy RP, Whitley JQ, Prewitt MJ: Comparison of the frictional coefficients for selected arch wire-bracket slot combinations in the dry and wet states, Angle Orthod 61:293, 1991.

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190. Sadowsky C, Schneider BJ, BeGole EA, et al: Long-term stability after orthodontic treatment: nonextraction with prolonged retention, Am J Orthod 106:243, 1994.

167. Oliver RG, Griffiths J: Different techniques of residual composite removal following debonding: time taken and surface enamel appearance, Br J Orthod 19:131, 1992.

191. Schaneveldt S, Foley TF: Bond strength comparison of moisture insensitive primers, Am J Orthod Dentofacial Orthop 122:267-273, 2002.

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246. Wood DP, Jordan RE, Way DC, et al: Bonding to porcelain and gold, Am J Orthod 89:194, 1986.

263. Zachrisson BU, Brobakken BO: Clinical comparison of direct versus indirect bonding with different bracket types and adhesives, Am J Orthod 74:62, 1978.

247. Zach L, Cohen G: Pulp response to externally applied heat, Oral Surg Oral Med Oral Pathol 19:515-530, 1965.

264. Zachrisson BU, Büyükyilmaz T: Recent advances in bonding to gold, amalgam, and porcelain, J Clin Orthod 27:661, 1993.

248. Zachrisson BU: Oral hygiene for orthodontic patients: current concepts and advice, Am J Orthod 66:487, 1974.

265. Zachrisson BU, Büyükyilmaz T, Zachrisson YØ: Improving orthodontic bonding to silver amalgam, Angle Orthod 65:35, 1995.

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254. Zachrisson BU: The bonded lingual retainer and multiple spacing of anterior teeth, J Clin Orthod 17:838, 1983.

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257. Zachrisson BU: Third-generation mandibular bonded lingual 3-3 retainer, J Clin Orthod 29:39, 1995.

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