Transfer accuracy of 3D printed trays for indirect bonding of custom 3D printed orthodontic brackets

Abstract

Objectives: To evaluate the transfer accuracy of custom orthodontic brackets using 3D printed transfer trays in a fully digital workflow. Methods and Materials: Twenty-one participants who were treated with LightForce (LightForce, Burlington, MA, USA) brackets were bonded using 3D printed transfer trays. Intraoral scans (iTero, Align Technology, San Jose, CA, USA) were taken after brackets were bonded. The virtual bracket setup was compared to post-bonding scans using digital model superimpositions. Discrepancies in bracket position were assessed, and one-sided t-tests were used to determine if the mean transfer discrepancies were within clinically acceptable limits of 0.5 mm in linear dimensions and 2° for angular dimensions. Results: The mean bracket position differences were 0.21 mm, 0.39 mm and 0.38 mm for mesiodistal, buccolingual, and occlusogingival directions, respectively. The frequency of bracket positions within 0.5 mm ranged from 73% to 95%. Mean bracket position differences were 1.69°, 1.09° and 1.70° for torque, tip, and rotation, respectively. The frequency of bracket positions within 2° ranged from 69% to 84%. P-values ranged from 0.00 to 0.694. The mean differences were statistically significant (p<0.05) and within clinically acceptable limits for all teeth in mesiodistal and tip dimensions. Conclusion: 3D printed transfer trays have high transfer accuracy in many dimensions. Bracket position discrepancies in angular dimensions are more frequent than in linear dimensions. A digital workflow using virtually planned bracket positions and 3D printed transfer trays, as judged from this study, may be implemented with clinical confidence in indirect bonding of orthodontic bracket.