[Tooth movement by biomechanical technique in orthodontic treatment]

The purpose of this study was to analyze tooth movement by measuring the electric impedance of the wire and by using the nonlinear finite element analysis. In this study, the HP4338A Milliohmmeter was used and the model consisted of a metal tooth, silicone bath, bracket, and orthodontic wire. Then, the two-dimensional finite elements were used and the model consisted of tooth, periodontal ligament, alveolar bone, bracket, and orthodontic wire. There were two analyses. The first was the contact nonlinear finite element analysis of elastic deformation in the displaced tooth at the slide points between the bracket and wire where two gap element areas existed, and the second was the material nonlinear finite element analysis of the stress relaxation in bone at the fixing points between the bracket and wire where two rigid element areas, differing from the gap element areas, existed. The results were as follows: 1. The linear proportion between the electric impedance and the orthodontic wire was found. Therefore very minute tooth movements became measurable with changes of the wire electric impedance. 2. During tooth movement, the stick between the bracket and the wire altered with the slip ones repeatedly. 3. The movement of the displaced tooth at the center of rotation was counterclockwise. 4. The movement of the displaced tooth at the bracket position was clockwise.