Stress Distribution in Periodontal Tissue at Initial Tooth Mobility.

Abstract

Initial movements of a lower first premolar were analyzed by a three dimensional elastic finite element method. When the elastic constants of the periodontal ligament were the following : Young's modulus Ep=0.2 MPa, Poisson's ratio νp=0.47, the calculated mobility values almost agreed with measured ones. In these case where the ratio of Young's modulus in alveolar bone Ep to Eb, Eb/Ep, became greater than 104, only the periodontal ligament was subjected elastic deformation whereas the tooth and the alveolar bone hardly deformed. Stress values calculated by the two dimensional plane strain model were about the half of the three dimensional case, because the stiffness of the alveolar socket decreases. Assuming that the tooth and the alveolar bone were rigid bodies, the initial movements and the stress distributions in the periodontal ligament were able to calculate simply. The results calculated by the simple method almost agreed with those by the finite element method.