External and Internal Reliability of Digital Indirect Bonding Technique Using Three Dimensional Models and Double Transfer Trays

Abstract

Introduction: Digital technology invaded all branches of orthodontics such as diagnostic aids, treatment planning, manufacturing of appliances and printing 3D models. there were many CAD programs to facilitate bracket placement more precisely and efficiently. there were many studies evaluated the efficacy and precision of digital indirect bonding approach and they found that it is effective strategy in general. However, there were limited research on the external reliability of digital indirect bonding approaches in literatures. Aim of the Study: To evaluate digitally the amount of discrepancy happened in bracket positions during transferring them by indirect bonding tray inside the patient’s mouth and external reliability of the measurements. Materials and Methods: Ten patients (4 males and 6 females), ranging from 15.9 to 23.4 years of age (mean 19.647 years, SD± 2.232), PVS impressions was taken for the upper arch of the patients and scanned by laboratory scanner to produce STL files to create digital models. digital indirect bonding of 100 American Orthodontic minimaster braces were performed on upper arch by positioning brackets on digital models using Ortho Analyzer (3Shape) software. Then, printing 3D model with braces and constructing the double transfer tray to be loaded with braces to bond it inside the patient’s mouth. After that, scanning of the bonded brackets was done by CEREC omnicam. Geomagic Control X software was used to measure the deviations happened in the bracket position on the patient’s mouth and the bracket position in Orthoanalyzer (3Shape) software. Results: Overall linear measurements were ranging from (-173.1±131.65 μm) to (200.2±132.86 μm). These deviations were related to occlusogingival and in-out directions and denoted to upper right first premolars and upper left canines respectively. Overall angular measurements were ranging from (0.51±0.03 degree) to (1.94±0.03 degree). These deviations were related to mesiodistal tip and denoted to upper right canines and upper left central incisors respectively. Discussion: The overall angular differences in the present study ranged from 0.51° to 1.94° and overall linear differences ranged from 0.1731 mm to 0.2002 mm, which agreed with those observed in the literature, confirming the reliability of the technique. Conclusion: Indirect bonding with a dual transfer tray can correctly replicate the position of brackets on digital models.