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Transfer accuracy of vinyl polysiloxane trays for indirect bonding
Thorsten Grünheid1, Michael S Lee2, Brent E Larson3
1a Assistant Professor, Division of Orthodontics, School of Dentistry, University of Minnesota, Minneapolis, MN.
Objective:
To elicit the magnitude, directional bias, and frequency of bracket positioning errors caused by the transfer of brackets from a dental cast to the patient's dentition in a clinical setting.
Materials And Methods:
A total of 136 brackets were evaluated. The brackets were placed on dental casts and scanned using cone beam computed tomography (CBCT) to capture 3-D positioning data. The brackets were then transferred to the patient's dentition with an indirect bonding method using vinyl polysiloxane (VPS) trays and later scanned using CBCT to capture the final bracket positioning on the teeth. Virtual models were constructed from the two sets of scan data and digitally superimposed utilizing best-fit, surface-based registration. Individual bracket positioning differences were quantified using customized software. One-tailed t tests were used to determine whether bracket positioning was within limits of 0.5 mm in the mesiodistal, buccolingual, and vertical dimensions, and 2° for torque, tip, and rotation.
Results:
Individual bracket positioning differences were not statistically significant, indicating, in general, final bracket positions within the selected limits. Transfer accuracy was lowest for torque (80.15%) and highest for mesiodistal and buccolingual bracket placement (both 98.53%). There was a modest directional bias toward the buccal and gingival.
Conclusion:
Indirect bonding using VPS trays transfers the planned bracket position from the dental cast to the patient's dentition with generally high positional accuracy.
