Date of Award
Master of Science (MS)
Introduction: Mechanical vibration (MV) possesses anti-resorptive properties that can possibly enhance the stability of the dentition during retention, lessening the potential for relapse of teeth to their initial positions. In this project, we established a mouse model and investigated the effects of MV on bone modeling during orthodontic retention. Materials and Methods: Thirty-two 14-week-old inbred strain C57BL/6 male mice were randomly assigned into four groups: 1) Control (N=6); 2) Mechanical Vibration (MV) (N =6); 3) Orthodontic Retention (OR) (N=9); and 4) Orthodontic Retention and Mechanical Vibration (ORMV) (N=11). All mice in OR and ORMV groups received approximately 10g of orthodontic force by a coil spring to move maxillary right 1st molar mesially for 10 days, followed by a retention period of 2 weeks. In MV and ORMV groups, the mice received MV (60 Hz, 0.3g) for 5min/day on the maxillary right 1st molar throughout the retention period. Micro-focus computed tomography (micro-CT) was used to quantify new bone formation through bone volume fraction (BVF), crestal bone heights and intermolar distances post-orthodontic retention. For each of the parameters, one-way ANOVA was used to examine whether there is a statistically significant difference among the 4 experimental groups, with Tukey comparison being used to determine the significant difference between each 2 groups (p < 0.05 is considered significant). Results: In general, mechanical vibration produced significant changes of alveolar bone height and bone volume fraction among the experimental groups. For the alveolar bone height (mm) at distal buccal root, the order from least to greatest was MV (0.23±0.021) < Control (0.24±0.045) < ORMV (0.31±0.073) < OR (0.33±0.092). For the BVF (%) at furcation of M1, the order from least to greatest was OR (0.49±0.134) < ORMV (0.52±0.078) < Control (0.62±0.072) < MV (0.66±0.082). For the BVF (%) at interproximal between M1 and M2, the order from least to greatest was OR (0.43±0.149) < ORMV (0.49±0.115) < Control (0.69±0.051) < MV (0.74±0.028). Conclusion: Mechanical vibration (60Hz, 0.3g, 5min/day) is able to increase the bone volume at furcation and interproximal and the crestal bone heights, indicating its potential clinical application to enhance the stability of orthodontic treatment.