Effect of Varying Frequencies of Mechanical Vibration on the Rate of Orthodontic Tooth Movement in Mice

Objective: The aim of this study is to utilize the Orthodontic Tooth Movement (OTM) model in a mouse in order to study the mechanical vibrational effects in bone. Specifically, we wish to test various frequencies of vibration under an orthodontic force to determine whether or not an increase in OTM is seen. We also intend to further investigate the role of osteoclasts in OTM and how they interplay with increasing tooth movement. Materials and Methods: Fifty-eight male CD1 mice were randomly placed into 1 of 8 groups. Three of these groups were part of the experimental subset which all received an orthodontic force in conjunction with either 5Hz, 10Hz or 20Hz vibration. The 5 control groups consisted of matching vibrations groups without the presence of an orthodontic force, along with a baseline control group and an orthodontic force only group. The orthodontic force application consists of a 10g Ni-Ti closed-coil spring connecting the maxillary right first molar and the maxillary central incisors, which is kept in place with steel ligatures at either end for a total of 14 days. During this time period, any mice that were part of a group that required mechanical vibration were then exposed to a vibratory force from a Bose Transducer to the occlusal surface of the molar every 3 days for 15-minute sessions. All animals were then sacrificed and underwent micro-CT analysis followed by histological staining for identification of osteoclasts in the area surrounding the maxillary first molar. Results: After 14 days of orthodontic force application, there was no difference in tooth movement between the different experimental groups. However, the maximum tooth movement was observed in the spring +5Hz group and was least in the spring only group. Micro-CT analysis showed a statistically significant decrease in bone volume fraction (BV/TV) when control groups were compared with experimental groups; however, differences in bone volume and tissue density were statistically insignificant between different experimental groups. Conclusion: From the findings of this study, we can conclude that mechanical vibration has no statistically significant effects on the amount of orthodontic tooth movement seen in a mouse model. However, we are currently increasing the sample size in hopes that a certain frequency will show a preferential finding.