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

Julia Süpple,Paul-Georg Jost-Brinkmann,Petra Julia Koch,Julius Von Glasenapp,Eva Hofmann

doi:10.3390/jcm10092002

Abstract

Objective: A digital workflow opens up new possibilities for the indirect bonding (IDB) of brackets. We tested if the printing orientation for bracket transfer models on the build platform of a 3D printer influences the accuracy of the following IDB method. We also evaluated the clinical acceptability of the IDB method combining digitally planned and printed transfer models with the conventional fabrication of pressure-molded transfer trays. Materials and Methods: In total, 27 digitally planned bracket transfer models were printed with both 15° and 75° angulation from horizontal plane on the build platform of a digital light processing (DLP) printer. Brackets were temporarily bonded to the transfer models and pressure-molded trays were produced on them. IDB was then performed using the trays on the respective plaster models. The plaster models were scanned with an optical scanner. Digitally planned pre-bonding and scanned post-bonding bracket positions were superimposed with a software and resulted in three linear and three angular deviations per bracket. Results: No statistically significant differences of the transfer accuracy of printed transfer models angulated 15° or 75° on the 3D printer build platform were found. About 97% of the linear and 82% of the angular deviations were within the clinically acceptable range of ±0.2 mm and ±1°, respectively. The highest inaccuracies in the linear dimension occurred in the vertical towards the gingival direction and in the angular dimension in palatal crown torque. Conclusion: For the IDB method used, the printing orientation on the build platform did not have a significant impact on the transfer accuracy.

Highlights

The scans were saved as standard tessellation language (STL) files and imported to the treatment simulation software OnyxCeph3TM
The linear mixed model shows no significant difference between Groups H and V in the linear or angular dimensions (Table 1)
We investigated the transfer accuracy within the clinical requirements for the indirect bonding (IDB) method

Summary

Introduction

F. Andrews introduced the straight-wire appliance and, ever since, accurate bracket placement has been an important objective for orthodontists. Tooth movement was no longer achieved by time-consuming wire-bending, but integrated into the bracket design with a predetermined slot angulation. Accurate bracket positioning of the straight-wire appliance is supposed to result in a correct slot angulation causing the intended tooth movement and treatment outcome [1,2]. Direct bonding is the most frequently used method to attach a straight-wire appliance to the patients’ teeth. Every bracket is bonded separately [3]. To accelerate and facilitate this process and to increase the comfort for patient and orthodontist, Silverman et al developed indirect bonding (IDB) in 1972. A laboratory-made transfer tray containing the brackets allowed to simultaneously bond them to a group of teeth

Methods

Results

Discussion

Conclusion