Indirect bonding of orthodontic Brackets: an evaluation of transfer accuracy and reliability

Abstract

Background: Indirect bonding of orthodontic brackets has been viewed as a method of achieving greater accuracy and effectiveness in orthodontic treatment. Although the concept of indirect bonding has been widely studied, the accuracy of the transfer between the indirect stone model-set of the brackets to the patient's dentition has not been investigated in a clinical setting. The goal of the present study is to elicit the frequency, directional bias, and magnitude of bracket positioning errors due to this transfer.Methods: A total of 163 brackets were initially placed on indirect stone model set-ups and scanned using a cone-beam computed tomography system to capture 3-D bracket positioning data. These brackets were then transferred to the patient's dentition and later scanned using CBCT to capture the final 3-D bracket positioning on the teeth. Virtual models of the teeth and attached brackets were constructed from the scanned data. Initial and final pairs of models were digitally superimposed. Differences in bracket positioning were measured using customized software. One-tailed t-tests were used to compare measurement data with the pre-determined acceptable ranges of +/- 0.5 mm linearly and 2.0 degrees angularly for differences in each of 6 dimensions studied. Results: The indirect transfer of brackets resulted in accurate positioning (&alpha = 0.05, P < 0.0001). Bracket positioning along mesial-distal, buccal-lingual, and vertical axis most frequently satisfied the accuracy requirements. The indirect bonding transfer of brackets had a modest bias towards the buccal and gingival. The bracket failure (detachment) rate in this study was 9.8%.Conclusions: The indirect bonding transfer is statistically accurate and reliable.