MECHANICAL PROPERTIES OF VENEERING PORCELAINS FOR ZIRCONIA CORE
Keywords:
veneering ceramic, all-ceramic, zirconia, flexural strength, biaxial test, tensileAbstract
Аll-ceramic prosthetic restorations are developed for better esthetic and higher biocompatibility, and their clinical performances are not sufficiently investigated, yet. Zirconium dioxide ceramic materials posses excellent strength and chemical stability, they come in different dentine colors for achieving natural aesthetics after veneering of the core. Smaller fractures of the veneering ceramic “chippings” are most common complications, but the reasons for their appearance are not yet clarified. The aim of the investigation was to evaluate flexure strength of three different zirconium veneering ceramics and one metal-ceramic to provide data for mechanical properties of the materials. Thirty ceramic discs from four different ceramic veneering materials were prepared. Ceramic specimens were then loaded with symmetrical forces and maximal loading on the central surface in Piston-on-three-ball biaxial bending test. Statistical analysis of the results showed different flexure strength of all four examined ceramic materials. Results showed the highest values for biaxial flexure strength test in Cercon Ceram Kiss 84.9 ± 13 MPa, VITA VM 9 80.2 ± 8 MPa, and the lowest strength for IPS e.max Ceram 73.0 ± 10.6 MPa. However, all veneering ceramics for zirconium showed lower values than veneering ceramic VMK Master for metal core. Tested veneering ceramics are strong materials with high compressive strength, but they are brittle and sensitive to tensile stresses. Tensile ceramic strength is very important for clinical success of the restorations. Improvement of the mechanical properties of the veneering ceramic for zirconium such as flexure strength is imperative for further investigations.
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