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: Soundness of stomatognathic system can be achieved with a functionally adequate occlusal contact.A study on this occlusal morphology requires the analysis of micro tooth movement as well as analysis of jaw movement. The purpose of this study was to investigate micro upper first premolar movement under several occlusal loading conditions. Our jaw tracking device was modified to develop the new motion analyzer in six-degree-of-freedom that can perform simultaneous measurement of tooth and jaw movements.The results were as follows :1. The resolution of the recording system was improved up to 1.3 pm for translation and 0.00017 for rotation.2. Three male adult volunteers were selected as the subjects. Movements of right upper first premolars against left upper first premolars of these subjects were measured with this device. Occlusal load was provided perpendicularly on buccal cusp, central fossa, palatal cusp and canine cusp. Directions of tooth movements of these subjects were almost the same under the same loading conditions.3. In some loading conditions, the rotation centers of tooth movement were found.

Abstract:The purpose of this research was to evaluate tooth movement in six degrees of freedom under occlusal force loading. The right side upper first premolar movement of an adult volunteer without any signs or symptoms of periodontal disease was studied. A small occlusal table mounted on a force transducer was clipped between the upper and lower dentition. Occlusal force was applied to the buccal cusp, palatal cusp or central fossa of the first premolar and also to the right side canine aspect by clenching this occlusal table.The right side first premolar movement relative to the left side first premolar was measured by means of a highresolution six degrees of freedom motion detector. The three-dimensional shape of the first premolar was measured with following methods. A 3-D digitizer with a touch sensor probe was used to measure the coronal part of a cast stone model of the tooth. Computerized tomography data were used to obtain the root shape of the tooth. These movement and configuration data were combined to perform computer graphics analysis of the three-dimensional tooth movements. The range and direction of tooth movement were varied by altering the position and amplitude of occlusal force loading. Since the magnitude of the tooth movements was relatively small, we adapted the screw axis (helical axis) concept to emphasize tooth movement on the computer graphics representations.

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