ポスト先端部の不適合が歯根歯質に及ぼす力学的影響

Abstract

Reconstruction of the crowns of non-vital teeth with posts can be a very useful technique. However, there are many cases where the length of the posts are insufficient, resulting in a poor fit and dead space at the apex of the post. The purpose of this study was to compare the post length to the depth of the post preparation using parallel X-ray films of 31 teeth (incisors, canines and premolars) and to locate the dead space at the apex of the post. In addition, stress analysis of the post-reconstructed upper central incisor models having five types of posts with dead space at the apex and two levels of supporting conditions were calculated using the finite element method. The results obtained were as follows: 1. From the roentogenographic survey, the depth of the post preparations averaged two thirds of the remaining root length, and one half the length of the root in bone. However, lengths of the posts were on the average 20% shorter than the depth of the post preparation. 2. As the dead space increased and supporting levels diminished, stresses of post-reconstructed teeth were found to increase gradually and to concentrate in the remaining dentin near the apex of the post.