Contamination of dental zirconia before final firing: Effects on mechanical properties

Abstract

Plate-like specimens were prepared, using a diamond saw, from Cercon —a pre-sintered yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) block. These specimens were treated with 10 kinds of dental materials which acted as contaminants, and then sintered at 1,350°C or 1,450°C. After the final firing, specimens were subjected to a three-point flexural test and Vickers hardness test. Their surfaces were also characterized by scanning electron microscopy and X-ray diffractometry. Phosphorus-containing contaminants reduced the three-point flexural strength and hardness of final sintered zirconia due to the formation of YPO₄ and phase transformation from tetragonal to monoclinic zirconia. Gypsum also reduced both mechanical properties due to the formation of CaZrO₃ and phase transformation from tetragonal to cubic zirconia. Other contaminants showed no adverse effects on the mechanical properties of final sintered zirconia.