Comparison of the transfer accuracy of two digital indirect bonding trays for labial bracket bonding

Abstract

Objectives To compare the transfer accuracy of two digital transfer trays, the three-dimensional printed (3D printed) tray and the vacuum-formed tray, in the indirect bonding of labial brackets. Materials and Methods Ten digital dental models were constructed by oral scans using an optical scanning system. 3D printed trays and vacuum-formed trays were obtained through the 3Shape indirect bonding system and rapid prototyping technology (10 in each group). Then labial brackets were transferred to 3D printed models, and the models with final bracket positioning were scanned. Linear (mesiodistal, vertical, buccolingual) and angular (angulation, torque, rotation) transfer errors were measured using GOM Inspect software. The mean transfer errors and prevalence of clinically acceptable errors (linear errors of ≤0.5 mm and angular errors of ≤2°) of two digital trays were compared using the Mann-Whitney U-test and the Chi-square test, respectively. Results The 3D printed tray had a lower mean mesiodistal transfer error (P < .01) and a higher prevalence of rotation error within the limit of 2° (P = .03) than did the vacuum-formed tray. Linear errors within 0.5 mm were higher than 90% for both groups, while torque errors within 2° were lowest at 50.9% and 52.9% for the 3D printed tray and vacuum-formed tray, respectively. Both groups had a directional bias toward the occlusal, mesial, and buccal. Conclusions The 3D printed tray generally scored better in terms of transfer accuracy than did the vacuum-formed tray. Both types of trays had better linear control than angular control of brackets.

Accurate Bracket Placement with an Indirect Bonding Method Using Digitally Designed Transfer Models Printed in Different Orientations—An In Vitro Study

“…Torque showed the worst transfer accuracies of all angular dimensions, and the same result was found in previous studies [ 5 , 7 , 14 , 16 ]. Nui et al refer to an excess of bonding material or the transfer tray design to explain the outcome for torque [ 16 ]. Most investigations though, lack an explanation for these results.…”

“…In our, and in previous studies, the greatest transfer inaccuracies in the linear dimension were found in the vertical direction [ 5 , 6 , 7 , 8 , 16 ]. Inconsistent pressure on the tray during the bonding process is often mentioned as an explanation for this [ 5 , 6 , 7 , 16 ]. Most authors found that the deviation was towards the occlusal direction.…”

“…Significant differences between the tooth groups and jaws were found in our study, as well as in others testing IDB workflows [ 5 , 16 ]. The shape of the tooth seems to play an important role for the transfer accuracy, as well as the accessibility that is worse in the posterior direction [ 6 , 7 , 25 , 26 ].…”

“…For the angular dimensions torque, rotation and tip, Niu et al found that they were generally less accurate than the linear dimensions [ 16 ]. This supports our results.…”

“…The 3D printing of IDB trays was investigated in only a few in vitro studies. The testing of different materials and designs endorses their clinical usability [ 12 , 13 , 14 , 15 , 16 ].…”