Potential for bracket bonding errors based on tray accuracy and fit: Evaluation of 6 photopolymer resins for indirect bonding trays

Introduction: We assessed the accuracy and fit of 3-dimensional (3D)-printed indirect bonding (IDB) trays fabricated using various photopolymer resin materials.

Methods: A maxillary plaster model and 60 plaster replicas were created. IDB trays with arbitrary bracket configurations were 3D-printed using 3 hard resins (Amber [AB], TC85DAC [TC], Orthoflex [OF]) and 3 soft resins (IBT [IT], IDB2 [ID], and MED625FLX [MD]). A reference plaster model with a computer-aided design-designed IDB tray attached with nonfunctional, arbitrary bracket configurations on the buccal surface serving as reference points for measurement was superimposed on scanned plaster replicas holding 3D-printed trays to assess transfer accuracy and clinically acceptable error. Printing accuracy was assessed by comparing computer-aided design trays to printed trays, and tray fit was measured by the gap volume between the tray and plaster replica using a Fit-Checker (GC Corp, Tokyo, Japan).

Results: Six tray groups showed significant linear transfer errors, particularly in the vertical direction (0.15 mm [95% confidence interval {CI}, 0.10-1.15]; P = 0.004). The OF group exhibited the largest vertical error (0.27 mm [95% CI, 0.19-0.35]), whereas the ID group had the smallest (0.10 mm [95% CI, 0.06-0.14]). Angular errors did not exhibit significant differences across the groups. Linear precision error was the highest in OF, followed by ID, TC, and MD, then AB and IT (P <0.001). Of all tray groups, 90.1% and 68.8% met the clinically acceptable linear (<0.25 mm) and angular errors (1°).

Conclusions: Linear errors, particularly vertical errors, are more material-dependent than angular errors. Gap volume alone was not a reliable predictor of IDB tray accuracy. Therefore, material-specific designs are needed to control the optimal fit and facilitate precise bracket placement.