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In The SA Lab
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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.
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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.
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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.
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