Effects of Zirconia Addition on Fracture Toughness and Bending Strength of Dental Porcelains

Abstract

Zirconia dispersed composite porcelains with glass and aluminous porcelain as matrix were prepared as models of dental porcelains. The bending strength and fracture toughness of the composite porcelains were examined. The bending strength and fracture toughness of composite porcelains containing 50wt% zirconia were 20 to 80% greater than in glass alone. However, bending strength and fracture toughness decreased upon the addition of zirconia at more than 50wt%. Moreover, in the case of aluminous porcelain as matrix, fracture toughness increased to a maximum value of 2.6MPa⋅m^1/2 by addition of 23wt% zirconia, twice the toughness of glass alone. On the other hand, no increase of bending strength was observed in this case. Deflection and bowing of cracks as well as microcracking effects were related to these increases of mechanical properties in zirconia dispersed composite porcelains.