Preparation of Glass-Ceramic Containing Crystalline Apatite and Magnesium Titanate for Dental Crowns

Abstract

Glass-ceramics that are useful for castable dental crown were searched for in the systems based on 3CaO⋅P2O5, MgO⋅TiO2 and CaO⋅MgO⋅2SiO2 (see Fig. 1 and Table 1). A glass composed of MgO 16.9, CaO 24.8, SiO2 16.3, TiO2 22.8, P2O5 15.7, CaF2 2.0, Al2O3 1.0, ZrO2 0.5, and MnO 0.01wt% which was melted at 1350°C could be shaped into a dental crown free from any defect, such as pores, devitrification products and chemical reaction products with a mold, by a conventional lost-wax process using a centrifugal casting machine (see Fig. 2). The glass in the shape of a dental crown was converted into a glass-ceramic similar to natural teeth in color and translucency without any deformation by heat treatment up to 940°C (see Figs. 3 and 4). The glass-ceramic contained crystalline apatite and magnesium titanate in fine grains (see Figs. 5 and 6). It was confirmed to accurately reproduce the original wax pattern (see Fig. 4). The glass-ceramic showed a density and thermal expansion coefficient similar to natural teeth; and the mechanical strength, Young's modulus and hardness were higher than those of the natural teeth. It also possessed excellent fracture toughness and chemical durability (see Table 2).