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Indirect Bonding with a Thermal Cured Composite
Indirect Bonding with a Thermal Cured Composite Elliott M. Moskowitz Clinicians have sought an alternative to the traditional direct bonding of orthodontic attachments in their quest to attain more accurate and precise bracket positioning while simplifying chairside procedures. An indirect bonding technique of orthodontic attachments is presented. A thermal cure composite resin is used along with a flexible but sturdy inner and outer trays. The thermal cured composite provides a virtually unlimited working time for the placement of orthodontic attachments. This technique has been shown to be predictable and highly reproducible. (Semin Orthod 2007;13:69-74.) © 2007 Elsevier Inc. All rights reserved.
he placement of orthodontic attachments remains one of the most fundamental and important procedures in clinical orthodontics. Indeed, whether the clinician uses any of the many variations of either preadjusted or standard Edgewise attachments, accuracy and precision of orthodontic attachment placement and predictable in-treatment orthodontic attachment retention are indispensable elements in the quest to attain superior individual tooth position as part of the overall orthodontic treatment effort. To that end, orthodontists have developed numerous direct and indirect techniques of orthodontic attachment placement. Proponents of indirect bonding cite advantages that include a greater accuracy of attachment placement and reduced chair time. Kalange1 has presented an extensive review of the clinical and technical advantages of indirect bonding techniques in orthodontic practice. Optimal use of clinical time and better staff use represent some of the collateral benefits also cited by Kalange. The author’s interest in indirect bonding was generated as a consequence of the recog-
T
Department of Orthodontics, New York University College of Dentistry, New York, NY. Address correspondence to Elliott M. Moskowitz, DDS, MSd, 11 Fifth Avenue, New York, NY 10003. Phone: 212-477-3871; E mail: [email protected] © 2007 Elsevier Inc. All rights reserved. 1073-8746/07/1301-0$30.00/0 doi:10.1053/j.sodo.2006.11.009
nition of some of the generic problems associated with direct bonding techniques. Difficulty in intraoral vertical and horizontal visualization of notably malposed teeth that frequently results in less-than-ideal bracket placement position, time restraints associated with composite cure (light-cured direct techniques have only modestly addressed this problem), clinician fatigue during a comprehensive bonding clinical session, and patient comfort issues were some of the more remarkable problems associated with direct bonding. An indirect method of orthodontic attachment placement is presented in this article that effectively eliminates or greatly minimizes many of the limitations of current direct and indirect bonding techniques. One of the unique features of this technique is the use of a thermally cured composite resin (ThermaCure, trademark of Reliance Orthodontic Products, Itasca, IL). The use of such a composite material has the advantage of creating a virtually unlimited working time so that orthodontic attachment placement can be performed in a contemplative stress-free environment thereby promoting more accurate and precise positioning of orthodontic brackets and other attachments.
The Technique The Thomas technique was an important advancement in contemporary indirect bonding.2
Seminars in Orthodontics, Vol 13, No 1 (March), 2007: pp 69-74
69
70
E.M. Moskowitz
In this procedure, the brackets, with filled composite on their bases, are bonded directly to the working casts. After bracket positions are accurately recorded with a plastic template, the unfilled resin (sealant) is added to both the tooth surfaces and the composite bases. The entire tray, with the brackets encased, is seated in place, resulting in minimal flash and relatively easy cleanup. The following indirect bonding technique3 is a modification of the Thomas technique and uses the following: 1. Thermally cured composite material. 2. Reprosil (trademark of L.D. Caulk Division, Dentsply International, Milford, DE)—a vinyl polysiloxane impression material (PVS) as a highly accurate but flexible inner tray that can be easily removed. 3. Vacuum-form Essix (Raintree Essix Inc., New Orleans, LA) 0.020 inch (0.5 mm) clear material tray that covers the PVS inner tray, which directly encases the brackets and other attachments.
Fabrication and Preparation of the Indirect Working Casts 1. Prophy the facial surfaces of the teeth with a rubber cup and pumice. 2. Take alginate impressions with either perforated or rim-lock metal trays. 3. The patient should be scheduled for the bonding procedure within a few weeks to minimize the chance that the teeth may drift. Procedures such as air-rotor stripping or extractions should be postponed until after bonding. If molar bands are used instead of bonded attachments, then the
Figure 2. (A and B) Brackets with ThermaCure composite resin on bases, positioned on casts. (Color version of figure is available online.)
4. 5.
6.
7.
banding should be done before impression taking or after the indirect bonding procedure. Pour the impressions immediately in a hard stone. After set, separate the casts from the impression trays. Voids in the casts should be filled with a light-cured adhesive gel (Triad, trademark of Dentsply/York Division, York, PA) and cured for 20 to 30 seconds. Bubbles or excess should be removed carefully because too zealous removal of such excess can interfere with the accuracy of transfer trays that will be fabricated on these casts. The long axis and the mesiodistal center points of the teeth to be bonded should be marked with a pencil as well as the preferred inciso-gingival positions of the bracket slots (Fig 1). Apply 1 or 2 coats of liquid separating medium to the facial surfaces of the teeth on the cast and allow to dry.
Bracket Placement Figure 1. Pencil marks drawn along the incisal edges, mesiodistal center points, and long axes of teeth to ensure proper bracket placement. (Color version of figure is available online.)
1. Place the ThermaCure composite resin on the pad of each bracket, taking care to cover all of the pad surfaces. 2. Place the brackets on each of the cast teeth with firm pressure and position them accord-
Thermal Cured Composite
71
ing to the pencil marks (Fig 2A and B). The ThermaCure provides virtually unlimited working time. 3. If assistants are placing the brackets, the orthodontist should check bracket positions and that excess adhesive around the bracket and molar attachments is removed. When mandibular arch attachments are placed, occlusal interferences should also be checked. The composite is now ready to cure.
Curing of Composite Resin 1. Place the casts in a heated oven (Fig 3) to cure (a toaster oven works well). ThermaCure requires 15 minutes at 325°F. It is important to use an oven thermometer, because temperatures may vary from oven to oven, especially when multiple casts are cured. 2. Allow the casts to cool, and remove them from the oven.
Figure 4. Light bodied polyvinylsiloxane (PVS) impression material applied with syringe over all brackets, extending onto occlusal or incisal surfaces and onto lingual surfaces. (Color version of figure is available online.)
Fabrication of Transfer Trays 1. Apply the Reprosil impression material with a syringe over the thermally cured brackets (Fig 4). Start with the facial surfaces, and be certain to cover each bracket. Extend the material onto the occlusal or incisal surfaces and onto the lingual surfaces, but do not make the undertray unnecessarily thick. 2. Vacuum-form Essix (trademark of Raintree Essix, Inc., New Orleans, LA) 0.020 inch (0.5 mm) or 0.030 inch (0.75 mm) clear thermoplastic material over the cast, brackets, and undertray complex (Fig 5A). After cutting away the excess thermoplastic mate-
Figure 3. Casts placed in toaster oven for curing at 325°F for 15 minutes. (Color version of figure is available online.)
Figure 5. (A and B) Essix 0.020-inch clear thermoplastic material vacuum-formed over casts, brackets, and undertray. Trays separated from casts and trimmed to final form. (Color version of figure is available online.)
72
E.M. Moskowitz
Figure 6. Inside of bracket-tray complex after washing and lightly abrading composite surfaces. (Color version of figure is available online.)
rial, soak the assembly in warm water for about 5 minutes, then separate both trays from the cast. The brackets will easily release from the stone and remain seated in the flexible undertray. Trim the trays with crown-and-bridge scissors (Fig 5B). Rinse away residual solidified material and other debris from the undertray and brackets. Inspect the composite pads, and trim off any flash.
Figure 8. (A and B) After an enamel bonding booster (Enhance) is applied to both the tooth surfaces and composite bases and allowed to dry, the unfilled bonding resin is mixed and quickly applied to the composite bases of the brackets and the teeth. (Color version of figure is available online.)
Chairside Bonding Procedure 1. To remove the air-inhibited layer of adhesive, lightly abrade the composite back of each bracket base with a Micro Etcher (trademark of Danville Engineering, Danville, CA), or simply scrape the composite base with a cleioid instrument (Fig 6).
Figure 7. The dental arches isolated, enamel surfaces etched, and etchant rinsed off. (Color version of figure is available online.)
2. Isolate a single arch, etch the enamel, and rinse off the etchant (Fig 7). 3. Mix 2 drops each of Enhance (Reliance Orthodontic Products, Itasca, IL) A and B primer. Apply the mixture to the composite bases and the tooth surfaces.
Figure 9. The trays are seated immediately and held in place for approximately 1 minute. They are allowed to remain undisturbed for 4 more minutes. (Color version of figure is available online.)
Thermal Cured Composite
Figure 10. The Essix outer tray is removed. (Color version of figure is available online.)
4. Mix unfilled bonding resin, and quickly apply it to the composite bases of the brackets and to the teeth (Fig 8A and B). 5. Seat the tray immediately (Fig 9). Hold the tray in place for 1 minute, then allow the tray to remain in place for about 4 more minutes. 6. Remove the clear overtray material (Fig 10). 7. Tease the flexible undertray from the teeth with an explorer or scaler (Fig 11) using a gentle, rolling motion from the lingual surface of the flexible tray to avoid dislodging the brackets. 8. Inspect the brackets. Floss interproximally to remove any bridging of the unfilled resin. There should be virtually no flash of filled bonding resin around the bracket bases (Fig 12).
Figure 11. The flexible undertray is teased away with an explorer or scaler without dislodging the brackets. (Color version of figure is available online.)
73
Figure 12. Any remaining unfilled resin can be removed by a scaler and dental floss interproximally. Wires are ready to be inserted. (Color version of figure is available online.)
Discussion The thermal-cured bonding composite, flexible undertray, and thermoplastic overtray all contribute to an indirect bonding technique that is highly predictable and consistently reproducible. The thermal cured adhesive allows precise bracket positioning in the laboratory without the time constraints associated with chemically and light-cured resins. The undertrays are accurate, stable, and compact, and will not dislodge the brackets from the teeth when removed. The Essix type of outer tray is flexible enough to be removed effortlessly while providing the needed strength and rigidity throughout the clinical procedures. This particular technique has considerable value in orthodontic postgraduate training programs. Residents, under the watchful eye of experienced faculty, can appreciate the merit of accurate orthodontic attachment placement performed in a contemplative manner using casts and panoramic radiographs before the actual intraoral placement of orthodontic attachments. With the sophistication of bracket design and the use of CAD/CAM technology, it is highly likely that the future of individualized and custom bracket fabrication will also include an equally sophisticated method of indirectly placing these attachments intraorally. As such, the clinician will be compelled to include the indirect bonding of orthodontic attachments in his/ her routine treatment protocols.4-6
References 1. Kalange J: Indirect bonding: a comprehensive review of the advantages. World J Orthod 5:301-307, 2004
74
E.M. Moskowitz
2. Thomas R: Indirect bonding: simplicity in action. J Clin Orthod 13:93-106, 1979 3. Moskowitz E, Knight D, Sheridan J, et al: A new look at indirect bonding. J Clin Orthod 30:277-281, 1996 4. Reichheld S, Ritucci R, Gianelly A: An indirect bonding technique. J Clin Orthod 24:21-24, 1990
5. Read JJF: Indirect bonding using a visible light cured adhesive. Br J Orthod 14:137-141, 1987 6. 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
he placement of orthodontic attachments remains one of the most fundamental and important procedures in clinical orthodontics. Indeed, whether the clinician uses any of the many variations of either preadjusted or standard Edgewise attachments, accuracy and precision of orthodontic attachment placement and predictable in-treatment orthodontic attachment retention are indispensable elements in the quest to attain superior individual tooth position as part of the overall orthodontic treatment effort. To that end, orthodontists have developed numerous direct and indirect techniques of orthodontic attachment placement. Proponents of indirect bonding cite advantages that include a greater accuracy of attachment placement and reduced chair time. Kalange1 has presented an extensive review of the clinical and technical advantages of indirect bonding techniques in orthodontic practice. Optimal use of clinical time and better staff use represent some of the collateral benefits also cited by Kalange. The author’s interest in indirect bonding was generated as a consequence of the recog-
T
Department of Orthodontics, New York University College of Dentistry, New York, NY. Address correspondence to Elliott M. Moskowitz, DDS, MSd, 11 Fifth Avenue, New York, NY 10003. Phone: 212-477-3871; E mail: [email protected] © 2007 Elsevier Inc. All rights reserved. 1073-8746/07/1301-0$30.00/0 doi:10.1053/j.sodo.2006.11.009
nition of some of the generic problems associated with direct bonding techniques. Difficulty in intraoral vertical and horizontal visualization of notably malposed teeth that frequently results in less-than-ideal bracket placement position, time restraints associated with composite cure (light-cured direct techniques have only modestly addressed this problem), clinician fatigue during a comprehensive bonding clinical session, and patient comfort issues were some of the more remarkable problems associated with direct bonding. An indirect method of orthodontic attachment placement is presented in this article that effectively eliminates or greatly minimizes many of the limitations of current direct and indirect bonding techniques. One of the unique features of this technique is the use of a thermally cured composite resin (ThermaCure, trademark of Reliance Orthodontic Products, Itasca, IL). The use of such a composite material has the advantage of creating a virtually unlimited working time so that orthodontic attachment placement can be performed in a contemplative stress-free environment thereby promoting more accurate and precise positioning of orthodontic brackets and other attachments.
The Technique The Thomas technique was an important advancement in contemporary indirect bonding.2
Seminars in Orthodontics, Vol 13, No 1 (March), 2007: pp 69-74
69
70
E.M. Moskowitz
In this procedure, the brackets, with filled composite on their bases, are bonded directly to the working casts. After bracket positions are accurately recorded with a plastic template, the unfilled resin (sealant) is added to both the tooth surfaces and the composite bases. The entire tray, with the brackets encased, is seated in place, resulting in minimal flash and relatively easy cleanup. The following indirect bonding technique3 is a modification of the Thomas technique and uses the following: 1. Thermally cured composite material. 2. Reprosil (trademark of L.D. Caulk Division, Dentsply International, Milford, DE)—a vinyl polysiloxane impression material (PVS) as a highly accurate but flexible inner tray that can be easily removed. 3. Vacuum-form Essix (Raintree Essix Inc., New Orleans, LA) 0.020 inch (0.5 mm) clear material tray that covers the PVS inner tray, which directly encases the brackets and other attachments.
Fabrication and Preparation of the Indirect Working Casts 1. Prophy the facial surfaces of the teeth with a rubber cup and pumice. 2. Take alginate impressions with either perforated or rim-lock metal trays. 3. The patient should be scheduled for the bonding procedure within a few weeks to minimize the chance that the teeth may drift. Procedures such as air-rotor stripping or extractions should be postponed until after bonding. If molar bands are used instead of bonded attachments, then the
Figure 2. (A and B) Brackets with ThermaCure composite resin on bases, positioned on casts. (Color version of figure is available online.)
4. 5.
6.
7.
banding should be done before impression taking or after the indirect bonding procedure. Pour the impressions immediately in a hard stone. After set, separate the casts from the impression trays. Voids in the casts should be filled with a light-cured adhesive gel (Triad, trademark of Dentsply/York Division, York, PA) and cured for 20 to 30 seconds. Bubbles or excess should be removed carefully because too zealous removal of such excess can interfere with the accuracy of transfer trays that will be fabricated on these casts. The long axis and the mesiodistal center points of the teeth to be bonded should be marked with a pencil as well as the preferred inciso-gingival positions of the bracket slots (Fig 1). Apply 1 or 2 coats of liquid separating medium to the facial surfaces of the teeth on the cast and allow to dry.
Bracket Placement Figure 1. Pencil marks drawn along the incisal edges, mesiodistal center points, and long axes of teeth to ensure proper bracket placement. (Color version of figure is available online.)
1. Place the ThermaCure composite resin on the pad of each bracket, taking care to cover all of the pad surfaces. 2. Place the brackets on each of the cast teeth with firm pressure and position them accord-
Thermal Cured Composite
71
ing to the pencil marks (Fig 2A and B). The ThermaCure provides virtually unlimited working time. 3. If assistants are placing the brackets, the orthodontist should check bracket positions and that excess adhesive around the bracket and molar attachments is removed. When mandibular arch attachments are placed, occlusal interferences should also be checked. The composite is now ready to cure.
Curing of Composite Resin 1. Place the casts in a heated oven (Fig 3) to cure (a toaster oven works well). ThermaCure requires 15 minutes at 325°F. It is important to use an oven thermometer, because temperatures may vary from oven to oven, especially when multiple casts are cured. 2. Allow the casts to cool, and remove them from the oven.
Figure 4. Light bodied polyvinylsiloxane (PVS) impression material applied with syringe over all brackets, extending onto occlusal or incisal surfaces and onto lingual surfaces. (Color version of figure is available online.)
Fabrication of Transfer Trays 1. Apply the Reprosil impression material with a syringe over the thermally cured brackets (Fig 4). Start with the facial surfaces, and be certain to cover each bracket. Extend the material onto the occlusal or incisal surfaces and onto the lingual surfaces, but do not make the undertray unnecessarily thick. 2. Vacuum-form Essix (trademark of Raintree Essix, Inc., New Orleans, LA) 0.020 inch (0.5 mm) or 0.030 inch (0.75 mm) clear thermoplastic material over the cast, brackets, and undertray complex (Fig 5A). After cutting away the excess thermoplastic mate-
Figure 3. Casts placed in toaster oven for curing at 325°F for 15 minutes. (Color version of figure is available online.)
Figure 5. (A and B) Essix 0.020-inch clear thermoplastic material vacuum-formed over casts, brackets, and undertray. Trays separated from casts and trimmed to final form. (Color version of figure is available online.)
72
E.M. Moskowitz
Figure 6. Inside of bracket-tray complex after washing and lightly abrading composite surfaces. (Color version of figure is available online.)
rial, soak the assembly in warm water for about 5 minutes, then separate both trays from the cast. The brackets will easily release from the stone and remain seated in the flexible undertray. Trim the trays with crown-and-bridge scissors (Fig 5B). Rinse away residual solidified material and other debris from the undertray and brackets. Inspect the composite pads, and trim off any flash.
Figure 8. (A and B) After an enamel bonding booster (Enhance) is applied to both the tooth surfaces and composite bases and allowed to dry, the unfilled bonding resin is mixed and quickly applied to the composite bases of the brackets and the teeth. (Color version of figure is available online.)
Chairside Bonding Procedure 1. To remove the air-inhibited layer of adhesive, lightly abrade the composite back of each bracket base with a Micro Etcher (trademark of Danville Engineering, Danville, CA), or simply scrape the composite base with a cleioid instrument (Fig 6).
Figure 7. The dental arches isolated, enamel surfaces etched, and etchant rinsed off. (Color version of figure is available online.)
2. Isolate a single arch, etch the enamel, and rinse off the etchant (Fig 7). 3. Mix 2 drops each of Enhance (Reliance Orthodontic Products, Itasca, IL) A and B primer. Apply the mixture to the composite bases and the tooth surfaces.
Figure 9. The trays are seated immediately and held in place for approximately 1 minute. They are allowed to remain undisturbed for 4 more minutes. (Color version of figure is available online.)
Thermal Cured Composite
Figure 10. The Essix outer tray is removed. (Color version of figure is available online.)
4. Mix unfilled bonding resin, and quickly apply it to the composite bases of the brackets and to the teeth (Fig 8A and B). 5. Seat the tray immediately (Fig 9). Hold the tray in place for 1 minute, then allow the tray to remain in place for about 4 more minutes. 6. Remove the clear overtray material (Fig 10). 7. Tease the flexible undertray from the teeth with an explorer or scaler (Fig 11) using a gentle, rolling motion from the lingual surface of the flexible tray to avoid dislodging the brackets. 8. Inspect the brackets. Floss interproximally to remove any bridging of the unfilled resin. There should be virtually no flash of filled bonding resin around the bracket bases (Fig 12).
Figure 11. The flexible undertray is teased away with an explorer or scaler without dislodging the brackets. (Color version of figure is available online.)
73
Figure 12. Any remaining unfilled resin can be removed by a scaler and dental floss interproximally. Wires are ready to be inserted. (Color version of figure is available online.)
Discussion The thermal-cured bonding composite, flexible undertray, and thermoplastic overtray all contribute to an indirect bonding technique that is highly predictable and consistently reproducible. The thermal cured adhesive allows precise bracket positioning in the laboratory without the time constraints associated with chemically and light-cured resins. The undertrays are accurate, stable, and compact, and will not dislodge the brackets from the teeth when removed. The Essix type of outer tray is flexible enough to be removed effortlessly while providing the needed strength and rigidity throughout the clinical procedures. This particular technique has considerable value in orthodontic postgraduate training programs. Residents, under the watchful eye of experienced faculty, can appreciate the merit of accurate orthodontic attachment placement performed in a contemplative manner using casts and panoramic radiographs before the actual intraoral placement of orthodontic attachments. With the sophistication of bracket design and the use of CAD/CAM technology, it is highly likely that the future of individualized and custom bracket fabrication will also include an equally sophisticated method of indirectly placing these attachments intraorally. As such, the clinician will be compelled to include the indirect bonding of orthodontic attachments in his/ her routine treatment protocols.4-6
References 1. Kalange J: Indirect bonding: a comprehensive review of the advantages. World J Orthod 5:301-307, 2004
74
E.M. Moskowitz
2. Thomas R: Indirect bonding: simplicity in action. J Clin Orthod 13:93-106, 1979 3. Moskowitz E, Knight D, Sheridan J, et al: A new look at indirect bonding. J Clin Orthod 30:277-281, 1996 4. Reichheld S, Ritucci R, Gianelly A: An indirect bonding technique. J Clin Orthod 24:21-24, 1990
5. Read JJF: Indirect bonding using a visible light cured adhesive. Br J Orthod 14:137-141, 1987 6. 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