有限要素法による維持装置こう腕のこう歯歯根膜への影響についての力学的研究 第２報 維持力およびきっ抗力について

Abstract

A direct retainer's arm is placed on an abutment tooth when an edentulous space is restored by the prosthetic treatment with a removable partial denture. Few analyses, however, have been reported about the effects of retainers on the abutment teeth when the denture base rotates toward and away from an edentulous ridge. A lower second premolar tooth was focused on, and the effects of an extracoronal direct retainer's arm to the periodontal ligament of the abutment tooth were analyzed utilizing the three-dimensional finite element techniques.The results were as follows:1. In case the retentive force is located on one side of a tooth and the reciprocal force on the other side, 1) the smallest von Mises stress (relative stress) on periodontal membrane was observed when the reciprocal force appears on the survey line rather than on the proximal surface, on the proximal-buccal corner and on the proximal-lingual corner, 2) and when the value of the reciprocal force is one-third of the retentive force, reciprocal force works appropriately.2. The proper retentive force is suggested to be lower than 205 g, considering the yield stress of periodontal membrane.3. It is desirable to make the guiding plane which limits the take-off direction of the denture by producing the reciprocal force on the neck of the retainer's arms when they are located on both sides of atooth.