Tracking orthodontic tooth movement and associated biomechanics using an integrated clinical and in vitro mechanical approach

Abstract

The objective of this study was to establish an integrated clinical and in vitro experimental approach to track tooth positions and replicate digital tooth positions in vitro for biomechanical load measurement over orthodontic treatment. Patients between 11–14 years were recruited to collect four digital intraoral scans in 4–6-week intervals. Patients were treated for mild anterior crowding using 0.022″ Damon Q2 brackets and CuNiTi round archwires sized up at each treatment interval (T1-T2: 0.014″, T2-T3: 0.016″, T3-T4: 0.018″). Scans were superimposed and clinical tooth movement was tracked using bracket-slot midpoint position differences. An in-house workflow was developed using MATLAB and SolidWorks to replicate digital bracket positions on an Orthodontic Simulator (OSIM) with custom-dimensioned jigs. Mechanical experiments for the sample arches were performed at 37°C for 3D force measurements at each tooth upon wire insertion (n = 5/archwire size). The average superimposition error between T2-T4 and T1 scans was 0.19 mm. Average errors in bracket position replication across all directions was 0.41 mm in the local X-, Y-, and Z-direction, respectively. The initial force and tooth movement range was 0.00–1.43 N and 0.01–1.81 mm in the Y-direction, and 0.01–2.17 N and 0.00–1.45 mm in the Z-direction. Tooth movement ranged from 0.00–0.30 mm/week in the Y-direction and 0.00–0.24 mm/week in the Z-direction over treatment. This study developed a process to measure clinical tooth movement and existing force/moment systems for sample arches over orthodontic braces treatment. Future work will involve an expanded data set to establish fundamental relationships between force systems and clinical tooth movements.