Technical Overview
for Indirect Bonding

We believe practices can better utilize the technique when they have an understanding of what processes occur in our laboratory to prepare and complete a case for Indirect Bonding. The following illustrate the detailed laboratory process used at Specialty Appliances Indirect Bonding Lab.

Incoming Quality Control on Models When we receive a case from your practice, we immediately perform a quality-control process on the models. Small bubbles and minor artifacts can usually be managed as we compensate for them in the model-preparation stages. If anything seems likely to jeopardize accuracy, we will telephone the practice to discuss the exact issue. In some cases, it may be necessary to obtain a new set of models. Click Any Photo for a Larger Image, Use Back Button to Return

Reference Lines on Models After we have verified the accuracy of the models, we place reference lines on the models for bracket placement. First, we mark the incisal and occlusal edges of all the teeth to receive brackets. These lines serve as visual references in aligning the brackets on the teeth with respect to the long axis and rotation. We then add the long axis lines on each tooth. This is best accomplished by viewing the models from several angles. Typically, the long axis line starts from the center of the incisal edge and follows up through the crown along a line reflecting the greatest curvature of the dental surface. Some practices prefer to mark the long axis in their office, using a panoramic radiograph as a reference.

Vertical Height Standards Followed We next add the vertical height reference lines to the models. Many practices have given us standard guidelines for their typical vertical heights used in placing brackets, and we mark the models in increments of _ mm for various heights. We also gauge and mark the vertical height of the teeth for bracket placement with regard to the overall size of the teeth. For patients with overall larger or smaller teeth, we will adjust the vertical heights on all teeth in proportion to the average measurements.

In the laboratory at Specialty Appliances the brackets are placed using several different methods depending on the clinicians’ preference. Our standard Indirect Bonding cases are processed using the "custom base" technique, however we also offer the "clean base" option. The clean base method can also be used with a light-cured clinical adhesive if you request the two-part clear transfer tray. The two-part clear transfer trays are not a standard with the clean base technique, so it is very important that you make a note on the prescription form when submitting the case.

The Custom Base Technique In our standard custom-base Indirect Bonding system, the brackets are placed on the models using a direct bonding adhesive such as "Phase II" from Reliance Orthodontic Products. We also provide systems in which light-cure or thermal cure composites are used to place the brackets. Only a thin film of bonding adhesive (light cure or auto cure) is necessary because of the precise fit of the custom base pads to each tooth.

Custom Base Adhesive Fit This is a close-up view of the custom base technique with its final base against the laboratory model. Note the exact fit of the adhesive to the dental surfaces. The two-tray bonding system ensures that the custom base pads will be in complete contact with the tooth surfaces during the clinical bonding process. This close adaptation once again emphasizes the need for absolute accuracy in impressions and models. Since the custom base pads fit the teeth on the laboratory model as shown, there is little room for error in the system.

The "Clean Base-Sugar Daddy" Technique The clean base method with a single silicone delivery tray is the original technique used in Indirect Bonding. Success with this approach depends on the clinical application of the paste (the precise amount) used to bond the brackets to the teeth. In this option, we use a water-soluble bracket adhesive. After the final trays have been completed, the water-soluble material is removed from the back of each bracket base and the mesh pads are exposed for bonding in the clinic.

Model Preparation for Tray Fabrication After the brackets are secured on the model, a small amount of silicone putty is used to block out any rotational wings, ball-hooks, or self-ligating clips to facilitate bracket removal from the tray after bonding; the pressure-forming machines such as the Biostar will force the material into any undercut areas left unattended in the model-preparation phase. If you are doing Indirect Bonding in your office, this critical step must be done. Also, when processing the second outer tray (described below) separating medium must be used over the inner tray to prevent them from fusing together in the Biostar.

The "Two-Tray" Transfer System Over many years at Specialty, we have refined a well-proven system using a "two-tray" method. In the first step, a flexible "inner tray" made from pressure-formed vinyl material covers the brackets. Next, a hard acrylic material is processed directly over the inner tray to act as a "carrying and simultaneous seating tray" exerting positive pressure to help set the brackets. This system also lets the clinician easily position and seat the trays while maintaining a clear field of view. All transfer trays are sectioned according to the doctor’s preference.

The "Inner" Transfer Tray This photograph shows the inner tray on the model. Note the block-out material in the inner tray. The inner tray is cut to extend slightly below the general line along the gingival border and extends over all dental surfaces on the lingual. An alternative inner tray design adds a vertical slit on both sides of each tooth in this tray. The resulting tabs can be peeled up individually to release the brackets from the tray. In some instances during clinical seating, the inner tray may be separated from the outer tray and seated first with a slight "flexing" as needed due to crowding or rotation of the teeth. The outer tray is then seated immediately over the inner tray.