Influence of fracture strength of zirconia ceramic restoration on thickness of veneer porcelain

The purpose of this study was to examine fracture strength of zirconia ceramic restoration on thickness of veneer porcelain. Specimens were made from zirconia core and veneering ceramic 0.5 mm (ZR5), 0.7 mm (ZR7), and 1.0 mm (ZR10), respectively. Metal ceramic restorations (PFM) with metal core and veneering porcelain in thickness 0.5 mm and 1.0 mm, respectively were used as control. Fracture strength of the specimens was measured using a universal testing machine (UTM). Fracture surface of the specimens was observed. The fracture strengths of each specimen group were 2627.1 (± 559.4) N (ZR5), 3476.1 (± 116.6) N (ZR7), 3821.3 (± 594.1) N (ZR10), and 5273.5 (± 538.4) N (PFM). As a result, the fracture strength of zirconia ceramic group increased as the thickness of veneering porcelain increased. The fracture strength of zirconia ceramic group (2627.1-3821.3 N) was lower than that of metal ceramic group (5273.5 N). Failure pattern of each specimen was perpendicular fracture lines directly of the lingual slope of the buccal cusp. The entire fracture was observed in zirconia ceramic group and the partial fracture only showed in metal ceramic group.