Effect of feldspar porcelain coating upon the wear behavior of zirconia dental crowns

Opposing dental surfaces, both natural teeth and restoration materials, are submitted to wear. The effect of the presence of feldspar porcelain coating upon the wear properties of dental zirconia opposing human teeth was evaluated using pin-on-plate test geometry. Human molar cusps performed as pins, coated and uncoated commercial zirconia performed as plates. Tests were carried out at room temperature in citric acid solution during 21,600 cycles, using 1 Hz, 1.96 N and 5 mm amplitude. Wear loss was measured by weighing the cusps before and after testing. The material loss of the plates was assessed by profilometry. Surface roughness and hydrophilicity of the plates' surfaces were evaluated by roughness and contact angle measurements.Results show higher mass loss for teeth tested against feldspar veneered plates, together with higher friction coefficient. No wear was detected on unveneered zirconia surfaces. Contact angle results show distinct affinity of veneered (25°) and unveneered zirconia (70°) surfaces towards distilled water.Porcelain coating of zirconia dental crowns affects tooth/crown wear behavior, resulting in increased wear of both the artificial crown and the opposing natural teeth. Coating should therefore be avoided in occlusal crown surfaces.