Compositional characteristics and hardness of acrylic and composite resin artificial teeth

Abstract

New types of artificial teeth are commercially available; however, evidence-based information regarding composition and properties is lacking. The purpose of this study was to qualify the compositional characteristics and hardness of new commercially available types of acrylic resin and composite resin artificial teeth. Twelve brands of 3 types (2 conventional acrylic resins, 3 cross-linked acrylic resins, and 7 composite resins) of artificial teeth were examined. The filler geometry and composition were observed using scanning electron microscopy and energy disperse x-ray analysis, respectively. Vickers hardness was determined for each layer of the polished cross-sectioned teeth. The inorganic content of the enamel layer was determined by thermogravimetric analysis with an ash method. The swelling behavior of the artificial teeth after 12 hours of methyl methacrylate immersion was observed to determine the cross-linking structure. The data were statistically analyzed using 1-way analysis of variance and Tukey's multiple comparison (alpha=.05). Examined teeth were composed of 2, 3, or 4 layers of resin. Different sizes and shapes of filler were found but were composed only of silicon oxide. Vickers hardness ranged from 17.4 to 47.0 kgf/mm(2). The inorganic content ranged from 0 to 42.8 mass%. The enamel layer of all teeth, except for 3 products, produced negligible swelling, and the base layer of all the teeth, except for 2 products, produced obvious swelling. A significant linear correlation was observed between hardness and inorganic content. Within the limitations of this study, differences in size, shape, distribution, and content of the silica filler and the cross-linking nature of the resin matrix were found among the commercial brands of artificial teeth evaluated.