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

Abstract

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 $(2.815°\pm 0.350°)\text{and 2-mm}\text{TP}T$ (2.368° ± 0.245°; 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.