ＩＰＳ Ｅｍｐｒｅｓｓクラウンの寸法変化と適合性に関する研究

Abstract

Various new ceramics available for all-ceramic crowns have been developed recently. More esthetic and stranger materials are demanded. IPS Empress (Ivoclar AG) is developed to realize these requirements. To fabricate this material, a vacuum-pressure pressing machine was developed, and the used technique is the conventional lost wax process. Since the system was produced for dental restoration, it is important to understand dimensional change of this material to obtain restorations with a good fit. A metal die with cylindrical tooth preparation was used to determine the rate of expansion/contraction of the restorations. The dimensional change of this material was measured after pressing and firing. Ceramic ingots for the staining technique tend to expand (0.08%) after pressing, but shrink (0.12%) after first firing and (0.18%) after fifth firing. Ceramic ingots for the layering technique tend to expand (0.10%) after pressing, but shrink (0.13%) after first firing and (0.21%) after fifth firing. Furthermore, anterior IPS Empress crowns were made on epoxy resin models of abutment with clinical shape and dimensions. The crowns and abutments were embedded in epoxy resin and sectioned to allow measurement of the space between crown and abutment tooth. Precementation cross-sectional measurement of internal adaptation without spacer ranged between 14.8 and 190.6μm. After firing, the distance between crown and die increased. Based on this in vitro study, the following conclusions can be made. It is important to obtain a good fit of IPS Empress crowns, to which application of the die spacer is indispensable, and to keep the number of firing cycles as few as possible.