Translucency, flexural strength, fracture toughness, fracture load of 3-unit FDPs, Martens hardness parameter and grain size of 3Y-TZP materials

Abstract

Objective: This investigation tested pre-shaded 3Y-TZP materials on optical, mechanical and structural properties and calculated correlations between these properties.

Methods: Seven A2-shaded 3Y-TZP zirconia materials were investigated on translucency (T) via UV-vis-spectrophotometer, fracture load of 3-unit FDPs (FL), biaxial flexural strength (FS), Chevron-Notch Beam (CNB), fracture toughness (K_IC) and Martens parameter (hardness: HM and indentation modulus: E_IT). FL, FS and K_IC were measured in a universal testing machine. The grain size was evaluated by scanning electron microscopy (SEM). Data was analyzed using one-way ANOVA followed by post hoc Scheffé, Kruskal-Wallis-, Mann-Whitney-U- and Pearson-test (p<0.05).

Results: For translucency, negative correlations were found with results of facture load (R=-0.444, p<0.001) and K_IC (R=-0.503, p<0.001). While a positive correlation was found between translucency and flexural strength (R=0.238, p=0.019), between fracture load and E_IT (R=0.227, p<0.029), between fracture load and K_IC (R=0.362, p<0.001) as well as between fracture load and the grain size (R=0.598, p=0.007). While the grain size positively correlated with E_IT (R=0.534, p=0.017) as well as E_IT with HM (R=0.720, p<0.001).

Significance: Despite of being based on the same raw material, tested zirconia materials significantly differed regarding optical, mechanical (except biaxial flexural strength and Martens hardness) and structural properties. Materials with highest optical properties were those with lowest mechanical properties (CER, COP).

Keywords: Biaxial flexural strength; Fracture load; Grain size analysis; Indentation modulus; Martens hardness; Mechanical properties; Optical properties; Pre-shade zirconia; Translucency.