Despite the accuracy and clinical time salvage, 90% of orthodontists do not use indirect bonding.1  Many reasons exist for this choice: materials expense, required laboratory technique, training of personnel, difficulty in achieving consistent and predictable bracket adhesion to the teeth and others.

Many clinicians feel that insufficient pressure causes the failure of brackets to bond to teeth with the indirect method. Polyvinylsiloxane and vacuum transfer trays often have excessive flexibility that prevents tight contact between brackets and teeth.

Two previous articles 2,3  described alternative indirect bonding methods that use a transfer tray made from a polymer of ethylene vinyl acetate applied with a hot-glue gun.Although this system provides less flexibility than previous ones, some orthodontists continue to feel that the hot glue transfer tray, like previous ones, does not place sufficient pressure against individual teeth.

The indirect bonding system described in this article has the advantage of accuracy and low cost, but additionally offers clinicians a method that allows them to bond teeth one by one, while placing individual pressure on each tooth.

Accurate alginate impressions taken with a mechanically spatulated mixture will give the laboratory smoother impressions to work with. Fill the impressions with vacuum-mixed stone, not plaster and rough-trim the models to allow access to the teeth, which should also be thoroughly cleared of bubbles and voids.

Traditionally, orthodontists have aligned brackets by measuring from the incisal edges or occlusal cusp to the middle of the selected teeth. Nevertheless, since molar cusp tips wear more than newly erupted premolars, that strategy guarantees super-eruption of the molars during leveling of the arches. Alignment of the marginal ridges rather than cusp tips holds the key to good posterior occlusion. 4

After the models have thoroughly dried, mark the vertical long axes of the teeth with a thin pencil line. Next, draw horizontal lines connecting the marginal ridges of each posterior tooth (Figure 1).

Figure 1

Since the second premolar is usually the last tooth to erupt, use it as the main reference to select a slot site near the middle of the tooth. Then use a compass to measure from the marginal ridge line to the middle of the second premolar, and that mark will become the slot site of all posterior teeth (Figure 2).

Transfer that measurement to all of the posterior teeth. Use the distance from the mandibular premolar cusp tip to its slot line to mark the mandibular central and lateral incisors. In the maxillary arch use the premolar cusp tip to slot line measurement to mark the central incisor. The maxillary lateral incisor will be set .25mm more incisally. The maxillary and mandibular canine slot lines are placed .5mm more gingivally than the premolars. When the bite needs opening, reduce the slot line to incisal edge anterior teeth distances; when closing the bite increase them (Figure 3).

Figure 3

After marking all of the teeth on the cast, apply two thick coats of separating liquid to all of the tooth surfaces and allow the separator to dry. This prevents the pencil marks from transferring to the transfer tray and ultimately to the patient’s teeth.

When the stone models are thoroughly dry, the laboratory technician can then place the brackets on the casts with a small amount of Aleene’s Tacky Glue,* (Aleene’s, Buellton, CA). It is an inexpensive, water-soluble adhesive often used by hobbyists (Figure 4).

Figure 4

The glue sets quickly and must be manipulated immediately to position brackets properly. The orthodontist can reposition any misplaced brackets with a small amount of fresh Tacky Glue (Figure 5). Painting the brackets with Pam or a silicone liquid lubricates them and makes it easier to remove the transfer trays after composite polymerization in the mouth.

Figure 5

Use the glue gun to form a molten matrix or transfer tray over the entire lingual and occlusal surfaces of the stone teeth and also on the brackets. Care should be taken not to extend the glue into the gingival tie wings; this will make it more difficult to remove the matrix and adds little to the transfer tray’s stiffness (Figure 6). The laboratory technician can pat the molten glue into a closer conformation using a wet finger before the glue hardens (Figure 7).

Figure 6	Figure 7

After the glue hardens submerge the trays and brackets in water for 30 – 60 minutes to dissolve the Tacky Glue and separate the matrix and brackets from the cast. Additional soaking of the separated matrices will allow easy brushing away of the remaining cement with a soft-bristle toothbrush and cold water (Figure 8).

Figure 8

The excess glue is trimmed from the matrix with scissors (Figure 9). A microetcher (Figure 10) will increase the surface area of the bracket mesh and subsequently increase the bond strength slightly,5  but care must be exercised to thoroughly clean all of the aluminum oxide powder out of the bracket mesh, since leaving powder will weaken the bond strength.

Figure 9	Figure 10

The transfer tray is now divided with scissors to make individual trays for each tooth (Figure 11).

Figure 11

Individual transfer trays have been made in a variety of ways,6,7  but fabricating them from hot glue matrices has proven simple, quick, effective and inexpensive. Separate trays offer several advantages:

• Bracket placement occurs one tooth at a time, and total attention can be focused on that tooth to the exclusion of others;
• The matrices are easily saved and can be used to recement broken brackets;
• Firm pressure can be applied to the designated tooth without affecting adjacent bondings.
• Separators can be applied to posterior teeth without fear of tooth movement that will render the transfer tray inaccurate.

Each matrix should have the number of the tooth written on it so as not to confuse them when cementing the brackets (Figure 12).

Figure 12

If the clinician feels that the patient’s teeth contain excessive concentrations of fluoride, the enamel should be microetched before acid etching. Microetching alone has little clinical effect,8  but microetching followed by a chemical etch greatly enlarges the bondable surface area of fluorosed enamel.9

I prefer to use a light-cured composite because a faster more thorough polymerization occurs with that material than with auto-cure materials, 10  and my clinical impression is that fewer immediate bond failures happen with these composites. Clinicians can select one of several light sensitive composite adhesives. Nevertheless, I prefer one that flows easily and offers little resistance to seating of the transfer tray such as Transbond** ( Registered trademark of 3M Unitek, 2724 S. Peck Road, Monrovia, CA 91916) or Ultra Band Lock*** ( Reliance Orthodontic Products, P.O. Box 678, Itasca, IL 60143) or Enlight**** (Ormco/A Company, 1717 Collins Ave. Orange, CA 92867).

The brackets in the individual matrices are loaded with composites and placed under amber protective plates to prevent premature polymerization of the light-cured composites from ambient light (Figure 13).

Figure 13

Teeth are cleaned of all plaque and microetched if necessary, and the teeth are then isolated with retractors. Although orthodontic clinicians can use a water-based, all-in-one, self-etching adhesive,11  a recent study has shown that traditional etch and bond techniques offer stronger bond strengths.12   I etch teeth with 37 percent phosphoric acid for 20 seconds and then rinse them thoroughly with water and dry them with dry, warm air. This prevents enamel contamination from oil or water in the compressed air supply.

The prepared teeth are then coated lightly with Transbond Moisture Insensitive Primer**** (MIP) (Registered trademark of 3M Unitek, 2724 S. Peck Road, Monrovia, CA 91016), and the brackets applied to the teeth one by one in their individual trays. The clinician seats the tray on the tooth and then holds firm pressure against the bracket, while the assistant cures the composite with the light. If regular visible light is used, 30-40 seconds is usually enough; however if a Power Slot tip***** (Reliance Orthodontic Products, P.O. Box 678, Itasca, IL 60143) (Figure 14) is used, then only 10-20 seconds per tooth is required for thorough curing.

Figure 14

By removing the single tooth transfer trays from the lingual, clinicians will have fewer instances of binding than if they approach removal from the facial surface of the teeth. Since the trays are numbered, they may be stored in the patient’s model box and used again to rebond a broken bracket. This insures that the bracket will return to its original position on the tooth and obviates changes in tooth position, which is particularly helpful when recementing lingual brackets.

Single tooth transfer trays have most of the advantages of all indirect bonding techniques, but they retain some small disadvantages:

• They are slower than bonding all of the teeth in one tray;
• They require more time and labor in the laboratory;
• The trays have more flexibility than a full-arch tray;
• The molars are sometimes difficult to access with the small trays; but if bands are used on the molars, separators can be placed without altering the positions of adjacent teeth.

Nevertheless, for those clinicians who prefer the certainty of adequate bonding pressure, single-tooth transfer trays offer an accurate and preferable method of bracket placement.

1 Gottlieb, E.L.; Nelson, A.H.; and Vogels, D.S.III: 1996 JCO Study of Orthodontic Diagnosis and Treatment Procedures, Part I: Results and trends. J. Clin. Orthod. 30:615-630, 1996.

2 White, L.W.: A new and improved indirect bonding technique. J. Clin. Orthod. 33:17-23, January 1999.

3 White, L.W.: An expedited indirect bonding technique. J. Clin. Orthod. 35: 36-41, January 2001.

4 Kalange, J. T.: Ideal appliance placement with APC brackets and indirect bonding. J. Clin. Orthod. 33: 516-526, September 1999.

5 Grabouski, J.K.; Staley, R.N.; Jakobsen, J.R.: Am. J. Orthod and Dentofacial Orthop. The effect of microetching on the b ond strength of metal brackets when bonded to previously bonded teeth: an in vitro study, 114: 452-460, October 1998.

6 Kim, T.; Bae, G.; Cho, J.: New indirect bonding method for lingual orthodontics. J. Clin. Orthod. 34: 348-350, June 2000.

7 Andreiko, C.: JCO interviews Craig Andreiko, D.D.S., M.S., on the Elan and Orthos systems. J. Clin. Orthod. 28: 459-472, August 1994.

8 Olsen, M.E.; Bishara, S.E.; Damon, P.; and Jakobsen, J.R.: Comparison of shear bond strength and surface structure between conventional acid etching and air-abrasion of human enamel, Am. J. Orthod. 112: 502-506. 1997.

9 Miller, R.A.: bonding fluorosed teeth: New materials for old problems, J. Clin. Orthod. 24: 424-427, 1995.

10 Eliades,T.; Eliades, G.; Brantley, W.A.; Johnston, W.M.: Polymerization efficiency of chemically cured and visible light-cured orthodontic adhesives: degree of cure, Am. J. Orthod. and Dentofacial Orthop. 108: 294-301, September 1995.

11 White, L.W.: Ibid.

12 Bishara, S.E.; Gordan, V.V.; VonWald, L; Olson, M.E.: Effect of an acidic primer on shear bond strength of orthodontic brackets, Am. J. Orthod. and Dentofacial Orthop. 114: 243-247, September 1998.