光・加熱重合による臼歯部硬質レジンクラウン内面の形状変化

Abstract

In order to clarify changes in the inner surface of posterior resin crowns in response to polymerization, changes in the contour of the inner surfaces of these crowns (1.0, 1.5 and 2.0 mm in thickness) under conditions of light polymerization or light and heat polymerization (heat polymerization) were determined by a three-dimensional measurement system, and changes with light polymerization were compared with those of heat polymerization. The results are summarized as follows:1. Under conditions of both light and heat polymerization, the inner surface shrank at all measurement sites and the amount of shrinkage with heat polymerization was greater than that with light polymerization.2. Under conditions of both light and heat polymerization, the amount of shrinkage was decreased in the region ranging from the occlusal surface to the dental neck, showing a claviform pattern. This tendency was marked under the light polymerization condition.3. Dimensional changes were observed, i.e., -16μm with light polymerization and -28μm with heat polymerizaiton, at a site 6 mm from the occlusal surface, -11μm with light polymerization and -30μm with heat polymerizaiton at a site 8 mm from the occlusal surface, and -8μm with light polymerization and -27μm with heat polymerization at the dental neck. There were significant differences in dimensional changes between light and heat polymerization at the site near the dental neck on the axial wall.4. When the thickness of the resin crown was 1.0, 1.5 or 2.0mm, the inner surface shrank at all of measurement sites. With the increase in thickness, the amount of constriction was increased.5. When the thickness of the resin crown was 1.0 or 1.5mm, the amount of shrinkage was decreased in the region ranging from the occlusal surface to the dental neck, showing a claviform pattern. When the thickness was 2.0mm, the amount of shrinkage was almost fixed. The ten-dency to form a claviform pattern with the 1.0mm-thick crown was greater than that with the 1.5 mm-thick crown.6. There were significant differences in all dimensional changes except height, at all measurement sites on the axial wall, between the 1.0mm-and 1.5 mm-thick crowns, and at all of measurement sites, except the occlusal surface, between the 1.0mm-and 2.0mm-thick crowns. There was a significant difference in the dimensional change of height between the 1.5mm-and 2.0mm-thick crowns.