Anaap Sandhi, DDS, MS'

Aim: To develop a cohesive and complete system for fabricating bonding trays and an effec-tive indirect bonding procedure. Material and Methods: A new resin designed specifically forindirect bonding has been developed. Previous problems with indirect bonding systems,which were partly related to the fact that resins designed for direct bonding had to be used,have been addressed. Conclusion: A cohesive and complete system for fabricating bondingtrays and for the indirect bonding procedure is presented. World J Orthod 2001;2:106-114.

DIRECT BOND1NGT he transition from removable to fixed appliancesmade greater precision in tooth movement possi-

ble. However, the initial fixed appliances attachedbrackets and tubes to the patient's teeth with bands,and there were significant limitations in the degreeof accuracy possible with these cemented bands.During the 1970s, two parallel developments had aprofound impact on orthodontic treatment with fixedappliances. The development of pretorqued and pre-angulated brackets permitted a more sophisticateddegree of detail in finishing the occlusion. Further,the development of direct bonding made greater pre-cision in the placement of these preadjusted brack-ets an achievable goal. It remains possible to moveteeth, and to achieve a good orthodontic result, with-out preadjusted appliances. However, a substantialimprovement in both the efficiency and the effective-ness of fixed appliance mechanics can now beachieved with the accurate placement of preadjustedbrackets. It has always been important that the fin-ished orthodontic result be esthetically and function-ally the achievable optimum, and our enhancedunderstanding of occlusion and occlusal functionhas been coupled with the efficient application ofbiomechanics in the design of increasingly advanced

preadjusted edgewise appliances.

The transition from banded attachments to directbonded attachments has significantly improvedorthodontists' ability to attain accurate bracket posi-tions. However, with chemically cured bondingresins, working time is fairly limited, and this pre-sents an additional challenge in trying to bond pos-terior teeth. The introduction of light-cured resins likeTransbond (3M Unitek, Monrovia, CA, USA) allowsincreased working time, thereby permitting signifi-cant latitude in positioning the brackets before theresin is cured. Despite this increased flexibility,achieving accurate and consistent bracket positionson posterior teeth continues to present a problem,due to poor access. Since rebonding brackets andtubes on posterior teeth is no easier than bondingthem the first time, bracket repositioning is bestkept to a minimum. Most clinicians direct bondbrackets on anterior teeth and premolars but avoiddirect bonding on molars. Indeed, some cliniciansprefer to band not only the molars, but also the sec-ond premolars.

INDIRECT BONDING

The concept of indirect bonding was first mentioned inthe literature during the mid- to late 1970s, and vari-ous modifications of the process have beenreported.1-6 In the initial efforts at indirect bonding,taffy candy was used to position brackets on the teeth,and filled chemically cured resins were employed to

1Private Practice of Orthodontics, Indianapolis, Indiana, USA.

REPRINT REQUESTS/CORRESPONDENCEDr Anoop Sandhi, 9333 North Meridian, Suite 301, Indianapolis,IN 46260, USA. E-mail: asondhi@ameritech.net

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Advantages of indirect bonding

There are significant advantages to indirect bonding:1-7

1. Bracket placement is accurate2. Use of the orthodontist's time is optimized.3. Band fitting on posterior teeth is avoided.4. Need for separators is eliminated.5. Ability to bond posterior teeth is improved.6. Patient comfort and hygiene are improved.

Disadvantages of indirect bonding

1. Indirect bonding is technique sensitive.2. Additional set of impressions is needed.3. Posterior attachments are more likely to fail if the

patient abuses the appliance by chewing ice, etc.

bond the brackets to the teeth. Although this methodwas effective, it generated a significant amount offlash, and cleaning up the resin presented a definiteproblem. The technique also was awkward and

I involved a significant amount of clinical and laboratory

time. Alternative adhesives have been tried over theyears, but all have proved only moderately successful.

The next major improvement in methodologyoccurred during the 1980s, when heat-cured resinsentered the market. However, there were reports ofclinicians experiencing problems with bracket floatduring the heating required to cure the resin. Castshad to be heated to 250°F to 300°F for approxi-mately 15 to 20 minutes to cure the resin (Therma-cure, Reliance Orthodontic Products, Itasca, IL, USA).Some nonceramic esthetic brackets could not beexposed to such heat, and had to be placed sepa-rately, after the metal brackets had been heatcured-a cumbersome procedure.

When the bracket bases are constructed withheat-cured resin, bonding placement is generallyaccomplished with chemically cured sealants orbonding resins. However, if a transparent tray isused, a light-cured resin with cure-on-demand bene-fits is an alternative.7

ACCURACY INBRACKET PLACEMENT

Orthodontic appliances are now engineered withincreasingly sophisticated computerized design anda vast array of tips, torques, labiolingual offsets, androtations are available to the clinician. However,some of this precision is lost when brackets areapplied to the teeth in an indiscriminate manner.

A number of bracket placement systems havebeen proposed over the years. To realize the fullpotential of a preadjusted edgewise appliance, thesystem for bracket placement must be reliable andconsistent. The orthodontist must be prepared toincorporate variations in bracket placement dictatedby the malocclusion. The positioning of bracketsclearly would be different in treatment of patientswith open bites versus patients with deep anterioroverbites. Kalange has proposed, for example, thatthe incisal edges of anterior teeth be recontouredprior to bracket placement.8 It is precisely this sortof variation that maximizes the efficiency of bracketplacement with indirect bonding.

Previous resins used inindirect bonding

With the increasing popularity of indirect bonding overthe past two decades, different methods of bondingthe brackets to the teeth have been developed. Ini-tially, brackets were positioned on the casts and thebonding was accomplished with a filled resin. Theindirect transfer trays were usually formed with sili-cone tray materials. The bond strength achieved withfilled resins was adequate, but the technique, particu-larly the clean-up, was difficult. It became apparentthat one of the deficiencies in the available systemsarose from the fact that all the resins and procedureshad been designed for direct bonding and had subse-quently been adapted for indirect bonding.

A generous window of working time is an impor-tant property in a resin designed for direct bonding.This property has no advantage in indirect bonding,since there is no need for an extended cure timeonce the tray has been placed in the mouth. There-fore, a resin designed specifically for indirect bond-ing was needed. After innovation, laboratory testing,and clinical trials, an efficient and effective indirectbonding procedure was created. One benefit of thisprocedure is that it does not require heating thecasts, since a custom base of the bracket is devel-oped with light-cured resin.

DEVELOPING A CUSTOMIZEDRESIN BASE

In an effort to determine the best method for prepar-ing a custom resin base, a number of clinical trialswere completed. It was the author's finding thatlight-cured resin is a quick and efficient material forplacing brackets on models and for forming a cus-tom resin base. Using adhesive precoated (APC)brackets. contamination is eliminated and laboratory

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Fig 1 (a) Anterior view of the working cast. (b) Occlusal view of the working cast. Note the detail of dental andsoft tissue structures, and an absence of any bubbles or voids. (c) Separating medium being applied to the maxillaryworking cast.

LABORATORVPROCEDURE

Preparation of the bonding traysby the technician

time is cut to a minimum, since individual bracketsdo not need to be sorted or have resin applied to thebase before placing on the model. If APC bracketsare not used, the author recommenps Transbond XTfor preparation of the resin bases. Other resins, withlighter viscosities, have proven to be ineffective dueto bracket float.

For the indirect bonding procedure, this cliniciannow uses the new indirect resin, with APC brackets(or Transbond XT adhesive applied in the lab), for thecustom base. This article provides a step-by-stepexplanation of the indirect bonding procedure.

A NEW INDIRECT BONDING RESIN

A resin designed specifically for indirect bonding wasdeveloped with the help of 3M Unitek (Sondhi Rapid-Set Indirect Bonding Resin, 3M Unitek). This materialwas designed with several objectives in mind. Anunfilled resin lacks any significant viscosity, and isnot capable of filling the small imperfections in thecustom base formed with light-cured resin or anyimperfections in the fit of the custom base againstthe enamel. The viscosity of this resin has beenincreased with the use of a fine-particle fumed silicafiller (approximately 5%), so that it is capable of fill-ing in such voids without compromising bondstrength. The resin was developed with a quick settime of 30 seconds, thereby significantly decreasingthe time needed to hold the bonding tray in place.The resin is completely cured in 2 minutes, allowingrelatively rapid removal of the bonding tray. Thisresin has been specifically designed for indirectbonding and would not be useful for direct bonding.

The complete indirect bo'nding procedure, fromthe laboratory process to clinical delivery of theappliance, is described and illustrated below.

1. Working casts in orthodontic stone, preparedfrom accurate alginate impressions, are neces-sary. Care should be taken to ensure that there isno distortion of the impressions. The workingcasts should be prepared with careful trimming,removal of bubbles, and filling of small voids. Ifthere are large bubbles or voids, it will affect thefit of the bonding tray (Figs 1a and 1b).

2. A thin layer of diluted AI-Cote (Dentsply Interna-tional, York, PA, USA) separating medium (1 to 4with water) should be applied to the model andallowed to dry for approximately 1 hour (Fig 1c).

3. If APC brackets are used, the preoriented bracketsmay be removed directly from the sealed blisterpack and positioned on the individual teeth. Theexcess adhesive should be removed, and the posi-tion of the bracket should be carefully checkedwith a bracket gauge. If noncoated brackets areused, Transbond XT Light Cure Adhesive should beplaced on the mesh pad of individual bracketsbefore they are positioned on the cast (Fig 2).

4. Once all brackets have been placed, a final checkof the bracket positions can be completed andthe excess resin removed. The casts should beplaced in the black plastic box provided with theresin, and left for final approval and positioningby the doctor (Figs 3 and 4).

5. When all the bracket positions have beenchecked, the maxillary and mandibular castsshould be placed in the TRIAD (TRIAD 2000,Dentsply International) curing unit and cured for10 minutes. Although the resin will cure morequickly, extra time is allowed to ensure complete

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Fig 2 APC brackets being placedon the teeth. If APC brackets arenot used, then Transbond XTshould be applied to the bracketbases.

Fig 3 Final bracket placement.checked by the orthodontist. Indi-rect bonding permits viewing thebrackets and casts in all threedimensions for optimal rotation andangulation.

Fig 4 Detail of the bonding set-up, which demonstrates the abilityto control axial inclinations of sec-ond molars with the initial arch-wire.

Fig 5 (Left) Indirect bonding casts placedin the TRIAD 2000 light-curing chamber. Therotating tray table permits light exposure tobracket bases from all directions.

Fig 6 (Below) Brackets are sprayed with alight cooking spray prior to forming the indi-rect bonding tray. This permits easier trayremoval following bonding of the brackets.

tics). The Bioplast layer is vacuformed onto thecast first, and the excess material is trimmed off(Figs 7a and 7b). The Bioplast surface should besprayed with a silicone spray or a light cookingspray before the Biocryl is adapted, which willpermit easier separation of the two layers. Thehard outer shell should be trimmed away from allheights of contour for patient comfort and closerfit, since its purpose is only to permit firm seatingof the soft tray. The outer layer provides rigidity tothe bonding tray, and the inner layer permits eas-ier removal of the tray (Figs 7c and 7d).

8. When a bonding tray made with a silicone transfermaterial is used, the Biostar unit is not necessary(Fig 8). A bonding tray can be made with a suit-able silicone transfer material. Once the putty hasbeen mixed with the activating agent, a small but-ton of the silicone material can be placed aroundindividual brackets, followed by the placement ofthe remaining material, which is rolled into the

curing because the access to light between theplaster cast and the bracket base is limited. Theamount of time for light curing is substantiallyreduced with clear esthetic brackets, and 1minute of exposure to the light should be ade-quate (Fig 5). Curing can be done with a chairsidelight-curing unit if a light chamber is not available.

6. Before forming the indirect bonding trays, a lightseparating spray should be used to facilitateeasy removal of the tray from the brackets. A sili-cone spray or a light cooking spray, such as Pam(International Home Foods, Parsippany, NJ, USA),may be used. The brackets should be sprayedlightly and for less than 1 second (Fig 6).

7. The indirect bonding trays can now be placedover the brackets. The author uses a Biostar(Great Lakes Orthodontics, Tonawanda, NY, USA)unit to vacuform a 1.5-mm-thick layer of Bioplast(Great Lakes Orthodontics) overlaid with a 0.75-mm-thick layer of Biocryl (Great Lakes Orthodon-

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I Sandhi WORLD JOURNAL OF ORTHODONTICS

Fig 7 (8) Cast with first layer of Bioplast. (b) The excess material around the base of thecast being trimmed. (c,d) Occlusal and lateral views of the indirect bonding tray. The hardouter shell of Biocryl provides rigidity to the tray.

Fig 8 (a) Superior view of an indirect bonding tray formed with Express silicone impressionmaterial. A putty tray of this kind can be used if a vacuformed tray is not desired or a Biostaris not available. (b) Posterior view of a silicone transfer tray, demonstrating bracket positionsand tray trimming around the hooks.

shape of a cylinder. The occlusal and lingual sur-faces of the teeth should also be covered with thetray material, as has been described by Kalange.8

9. The casts are soaked for approximately 1 hour topermit the separating medium to dissolve. Thisallows easier separation of the bonding trays. Thebonding trays are now removed from the casts andshould be sectioned off with a bur (Fig 9a). It maybe necessary to tease the tray off with a scaler.Any excess material should be trimmed with crownand bridge scissors or a scalpel. Once the bonding

trays have been trimmed, they should be placed inthe TRIAD unit for an additional minute to ensurethat any uncured resin is cured (Fig 9b).

10. The trays should now be cleaned with a dish-washing detergent (eg, Dawn, Proctor & Gamble,Cincinnati, OH, USA) in an ultrasonic cleaner for10 minutes. The trays are then run through theultrasonic cleaner, in water only, for an additional5 minutes. They are then rinsed and dried thor-oughly (Fig 10 shows external and internal viewsof the maxillary bonding tray).

11n

Fig 9 (a) Vacuformed indirect bonding tray is removed from the cast. (b) Trimmed indirectbonding trays in the TRIAD chamber for additional curing. One minute of additional curing isrecommended to ensure complete curing of the resin base.

Fig 10 External and internal views of a maxillary bonding tray.

CLINICAL PROCEDURE 5. If there are bands to fit. this should be doneafter the indirect bonding procedure has beencompleted. The resin used in this indirect bond-ing system has a fast set time, and the band fit-ting can be started immediately.

Preparing the patient

1. Seat the patient and place a napkin around hisneck. The author recommends the use of ananti-sialagogue, such as Sal-Tropine (Hope Phar-maceuticals, Scottsdale, AZ, USA). Patientsshould be instructed to remove contact lenseswhen they take the anti-sialagogue tablet. Inaddition, the orthodontist should be familiar withall contraindications prior to recommending ananti-sialagogue.

2. Pumice all teeth. Explain to the patient that thisis one of several procedures in preparation forbonding.

3. Rinse the mouth and suction well with water.4. Show the bonding trays to the patient and

explain the procedure-from taking the impres-sions to placing the brackets in proper positionand forming the tray. It is important to stress thetime the orthodontist takes to position the brack-ets and supervise the entire process. There issignificant value in emphasizing the importanceof proper bracket placement, and the doctor'sinput on appliance design, to the patient.

Placement of bonding trays

1. Whether the indirect bonding procedure can becompleted with a single tray for the entire arch,or whether the tray needs to be sectioned intotwo segments, is a decision based primarily onthe degree of isolation that is feasible. If there issignificant crowding and imbrication of the teeth,it may be easier to section the tray. Since theworking time with the indirect bonding resin isvirtually unlimited, as the adhesive does notneed to be mixed, the degree of isolation andease of tray placement are the determining fac-tors. On rare occasions, it may be advisable tosection the tray into thirds, in which case thetrays may be sectioned as follows:. Teeth 13 to 23 or 33 to 43 (anterior segment). Teeth 14 to 17 or 24 to 27; 34 to 37 or 44 to

47 (posterior segment)

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ance is not apparent, repeat the etching processfor 15 seconds.

10. Small amounts of the Resin A and Resin B liq-uids should be poured into the wells (Figs 12aand 12b). Take care to keep liquids separate.Resin A can be painted onto the tooth surfacewith a brush, and Resin B can be painted on theresin pads in the indirect bonding tray (Figs 12cand 12d).

11. If too much resin has been placed on theenamel, gently remove the excess with a brush.The overall method of painting the resin on theenamel and the custom bases is similar to paint-

ing fingernails.12. Position the tray over the teeth and seat the tray

with a hinge motion. With the fingers, apply equalpressure to the occlusal, labial, and buccal sur-faces. Hold for a minimum of 30 seconds (Fig13a). Figure 13b shows the maxillary and man-dibular bonding trays in place. Allow 2 more min-utes of curing time before removing the trays. Dueto the rapid set time of this adhesive, removal ofthe first tray can begin once the opposing tray isplaced (Fig 14). Figure 15 shows the completedappliance placement.

13. Remove the tray by using a scaler to peel thetray from the lingual to buccal. Use extremecare when removing the tray from aroundbracket wings. Scale the excess resin aroundthe brackets and from the interproximal con-tacts. Use dental floss to check that all contactsare open.

14. Repeat steps 4 to 13 for the remaining trays.15. The initial archwire can now be inserted (Fig 16).

RESULTS

2. Carefully examine the trays for any remainingseparator or tray material that may be coveringthe adhesive custom base on the bracket. Use amicroetching unit to lightly sandblast the adhe-sive custom bases. A fine aluminum oxide parti-cle (50 ~m) is recommended. Be careful not toabrade the resin base.

3. If there is any contamination of the adhesivecustom bases, especially if you touch them withyour fingertips, the trays should be cleaned witha detergent, rinsed, and dried. The application ofacetone to adhesive bases is not recommended,since recent research has indicated that thismay have a degrading effect on the resin.

4. Isolate the teeth that are to be bonded, using theNola (Nola Specialties, Hilton Head, SC, USA)dry-field system. If necessary, plastic cheek

retractors, Tongue Away (TP Orthodontics,laPorte, IN, USA), cotton rolls, and Dri-Angles(Young Dental, Earth City, MO, USA) may beused.

5. Dry teeth thoroughly with an air syringe.6. Dab (do not rub) etching solution onto teeth and

set stopwatch for 15 seconds. The etching solu-tion should be applied with extreme care; do notallow it to contact skin or gingiva. The etchshould be applied in the general area that is tobe covered by the bracket. Do not allow the etchto flow into the interproximal contacts. The clean-up will go more smoothly if this is kept in mind

(Fig 11a).7. Wait 15 seconds and then rinse with a steady

stream of water for 15 seconds. Rinse with asteady spray of water and air for another 30 sec-onds. Suction excess water and do not allowsaliva to come into contact with the etchedenamel (Fig 11b and 11c).

8. Replace cotton rolls and Dri-Angles; again, mak-ing sure that saliva does not contact the etchedenamel.

9. If the clinician chooses to use a moisture insen-sitive primer, such as Transbond MIP, on theenamel surface for the indirect bonding proce-dure, then the air syringe should be used toremove excess moisture. Complete desiccationof the teeth is optional. A liberal coat of Trans-bond MIP should be painted onto the enamelsurface. Air dry for approximately 2 seconds.Light curing of this primer is not necessary forindirect bonding. If Transbond MIP moistureinsensitive primer is not used, and the bondingis accomplished with the indirect bonding resin,then all visible moisture should be removed. Theetched teeth should have a frosty appearance,and be completely desiccated. If a frosty appear-~

This system has been used by thousands of clini-cians internationally, and several thousand patientshave been treated. Communication with orthodon-tists who have used this system indicates that thebonding is relatively consistent and efficient. Occa-sional bond failures do occur, of course, and areusually related to contamination or improper tech-nique. In those cases, it is a simple matter to sectionthe bonding tray, reapply the adhesive, and reseatthe brackets.

Bond strength tests have also proved the efficacyof the resin. Bond strength compares favorably withindirect bonding using Concise Enamel Bond (3MUnitek) and Custom IQ (Reliance). Figure 17 (shownon the web edition of the Journal at http://www.

quintpub.com) provides important bond strengthdata. The indirect resin shows substantially greater

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VOLUME 2, NUMBER 2, 2001 Sandhi I

Fig 11 (a) Enamel surfaces are etched with a gel etching material in preparation for bonding. (b,c) Enamel is rinsedafter removal of the etching gel. Note that the entire arch can be etched and dried to permit bonding of the com-plete dental arch.

Fig 12 (a,b) Dispensing wells are supplied with the indirect resin. Resin A is app)ied to thetooth surface and should be placed in the well identified with the tooth icon. Resin B isapplied to the bracket base and should be placed in the well with the bracket icon. (c) Resin Ais applied to the etched tooth surface. (d) Resin B being applied to the bracket base.

Fig 13 (a) Placement of the bonding tray. (b) Maxillary and mandibularbonding trays in place.

Fig 14 Removal of the outer shellof the mandibular bonding tray. TheBiocryl layer will lift off easily if thetwo layers were separated duringlaboratory preparation. The softBioplast layer is then remo,!ed.

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.

Fig 15 (a) Lateral view of right buccal segments of the indirect bondedappliance. (b) Anterior view of complete indirect bonded appliance. (c) Lat-eral view of the left buccal segments of the indirect bonded appliance. (d)Maxillary occlusal view of the indirect bonded appliance. (e) Mandibularocclusal view of the indirect bonded appliance.

Fig 16 Initial archwires engaged.Note the control over second molarpositioning with the initial levelingarchwire.

bond strength immediately after curing than theother resins, which is of critical importance duringtray removal and initial archwire insertion. Althoughthe final bond strength is not significantly different,the clinical efficiency of this resin is enhanced by itshigher bond strength at the 5-minute level, sincethat is when the indirect bonding tray would beremoved and the archwire inserted.

ACKNOWLEDGMENTThe step-by-step procedure outlined in this article originally

appeared in the April 1999 issue of the American Journal ofOrthodontics and Dentofacial Orthopedics.

REFERENCES

CONCLUSION

A new method for effective and efficient indirect bond-ing of orthodontic brackets has been presented. Thecustom adhesive bases are easily formed with Trans-bond XT or APC brackets, and the indirect bonding isaccomplished using a resin developed specifically forthis purpose. Bond strength has proven to be excellent,and this system for the indirect bonding of completedental arches, from second molar to second molar, hasbeen used in pediatric, adult, and orthognathic cases.

Bond strength tests have also proved the efficacyof this resin.9 Although the eventual bond strength iscomparable to that of other resins, the clinical effi-ciency of this resin is greatly enhanced by the higherbond strength developed within the first 2 minutes.Tray removal is therefore possible within 2 minutes,and archwire insertion can be immediate.

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5. Scholz R. Indirect bonding revisited. J Clin Orthod 1983;17:

529-536.6. Moskowitz EM, Knight LD, Sheridan JJ, Esmay T, Kruno T. A

new look at indirect bonding. J Clin Orthod 1996;30:

277-281.7. Kasrovi P, Timmins S, Shen A. A new approach to indirect

bonding using light-cure composites. Am J Orthod DentofacialOrthop 1997;111:652-666.

8. Kalange J. Ideal appliance placement with APC brackets and

indirect bonding. J Clin Orthod 1999;33:516-526.9. Sondhi A. Efficient and effective indirect bonding. Am J

Orthod Dentofacial Orthop 1999;115:352-359.

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