A new method for qualitative and quantitative evaluation of tooth displacement under the application of orthodontic forces using magnetic sensors

The purpose of this study was to develop a new method for the quantitative and qualitative measurement of tooth displacement under load and to clarify the relationship between the force system acting on a tooth and a resultan t movement. A combination of eight magnetic sensors and a magnet was employ ed to measure three-dimensional displacement. Two sets of sensors and a mag net were placed in front and at the back of a front tooth subjected to orth odontic forces. Magnets and sensors were fixed to the subject tooth and pos terior teeth, respectively. Sensors detected displacements of two magnets e xtended from the subject tooth separately in real time. The tooth trajector ies projected on the sagittal plane were studied. From displacements of two magnets, angle of tooth rotation, the position of center of rotation and t he amount and direction of displacement of an arbitrary point on the tooth could be calculated with high accuracy. Also, the location of center of res istance could be determined. It was found that the center of rotation is mo ving substantially even with a small difference in the level of force appli cation. Furthermore, a small amount of displacement of the center of resist ance was observed with varying the force magnitude. (C) 2000 IPEM. Publishe d by Elsevier Science Ltd. All rights reserved.