Bilateral Symmetry in a New Three-dimensional Orthodontic Force Measuring System

Objectives: In orthodontic treatment using multi-bracket appliances, it is critical to understand the distribution of force and moment acting on brackets by an archwire. However, few studies have measured the three-dimensional distribution of force and moment in orthodontic treatment. This study evaluated bilateral symmetry in the measurements of a newly developed three-dimensional orthodontic force measuring system in a simulation of mandibular central incisor linguoversion. Methods: A three-dimensional orthodontic force measurement system was developed to measure the three-dimensional distribution of force and moment acting on brackets in simulated orthodontic treatment. The system is comprised of 4 six-axis sensors connected to 4 simulated incisors. In this study, force and moment in a simulated case of 2.0mm mandibular central incisor linguoversion were measured using this system. Self-ligating brackets (DamonQ, Ormco, Orange, CA) were bonded to plastic teeth in a dental arch and the 4 simulated teeth. A 0.015inch twisted wire (Respond, Ormco, Orange, CA) was placed on the brackets. Measurements of force and moment on the artificial teeth were repeated 5 times using new wires for each measurement. Mean ± SD values for force and moment were calculated. Additionally, to examine the accuracy of this system, the correlation coefficient between the mean values in right and left central incisor linguoversion was statistically analyzed. Results: The mean force for the 4 incisors ranged from -185gf to 288gf. The mean moment for the 4 incisors ranged from -534gf-cm to 872gf-cm. A significant correlation coefficient of 0.97 was observed between mean values in right and left central incisor linguoversion (P<0.01). Conclusion: These findings demonstrate the accuracy of this system, and suggested that this system is suitable for measuring force and moment three-dimensionally in simulated 2.0mm central incisor linguoversion cases.