Comparison of 1- and 3-piece directly 3-dimensional printed indirect bonding trays: An in vitro study.

INTRODUCTION: This study aimed to compare the transfer accuracy of indirect bonding trays of different thicknesses and numbers of pieces. METHODS: Digital indirect bonding was performed on 56 printed resin models, divided into 4 groups with 14 models in each: 1-mm 1-piece tray (OPT), 2-mm OPT, 1-mm 3-piece tray (TPT), and 2-mm TPT. The trays were designed using Appliance Designer (3Shape A/S, Copenhagen, Denmark). Angular (torque, tip, or angulation) and linear (mesiodistal, buccolingual, occlusogingival, or vertical) differences were compared by using open-source GOM Inspect software (GOM GmbH, Braunschweig, Germany). RESULTS: In the buccolingual direction, the 1-mm TPT (0.180 +/- 0.041 mm) was significantly more accurate than the 1-mm OPT (0.240 +/- 0.032 mm). In the vertical direction, significant differences were seen between the 1-mm and 2-mm OPTs (1-mm OPT: 0.220 +/- 0.043 mm; 2-mm OPT: 0.428 +/- 0.143 mm; P = 0.003) and between the 1-mm and 2-mm TPTs (1-mm TPT: 0.210 +/- 0.072 mm; 2-mm TPT: 0.340 +/- 0.062 mm; P = 0.004) in the total region. In the tip angle, significant differences were seen between the 1-mm and 2-mm OPTs and between the 1-mm OPT and TPT. In the torque angle, a significant difference was seen between the 1-mm TPT (2.815 degrees +/-0.350 degrees )and 2-mmTPT (2.368 degrees +/- 0.245 degrees ; P = 0.017). CONCLUSIONS: Both the thickness and the splitting of the trays impacted the bracket bonding accuracy. The 1-mm trays were more accurate than the 2-mm trays. Despite a few statistically significant differences between the 1-mm OPT and TPT, the 1-mm OPT was recommended for clinical use, considering the designing and placing of the trays.