Abstract
Biting force during functional movements reaches over the teeth, periodontal ligament, mandible and maxilla. It produces distortion in each part. This distortion corresponds to the biting force and influences occlusion. Many studies, therefore, have been made on this subject. But it is not necessarily easy to measure the distortion of periodontal tissues during function in man. The purpose of this paper is to clarify the influence of the distortion of periodontal tissues on physiological tooth movements. The horizontal movements of the upper first molar were measured during function. The upper first molar had made preparation for a cast crown. It had no occlusal and proximal contacts with antagonistic and proximal teeth, so that it did not directly recieve the bite force. The following conclusions were obtained:
1. The movements of the upper first molar, caused by the distortion of periodontal tissues, were influenced by the acting point of the bite force.
2. The movements of the abutment tooth during function were similar to the physiological tooth movements.
3. In the prosthodontic treatment, it is very important to reconstruct an occusal contact not to disturb the tooth movements caused by the distortion of periodontal tissues during function.
