Effect of different surface treatments on the surface roughness and hardness of dental porcelain

Traditionally, glazing has always been advocated as the last surface treatment before final cementation. However, occasions will arise when porcelain restorations require adjustment in circumstances that preclude reglazing. Roughness created by adjusting the porcelain must be smoothed. The objective of this study was to compare the surface roughness (Ra) and Vickers hardness number (VHN) of porcelain (Ceramco) applied different surface treatments and to determine efficiency of the silicone polishers (Ceramiste polishers) under the simulated laboratory and clinical circumstances, with the use of scanning electron microscopy (SEM), surface profilometry and microhardness indentation tester. 48 porcelain specimens were prepared They were divided into six groups The following various surface treatments were applied. 8 specimens in each group were unglazed (GI); mechanically polished (GII); mechanically polished then glazed (GIII); glazed (GIV); glazed and then mechanically polished (GV); glazed, ground with fine grade diamond bur and then mechanically polished (GVI). Unglazed surface of porcelain was the roughest surface while the porcelain surface obtained by mechanic polishing after glaze was the smoothest surface. Glazed, ground and polished surface of porcelain was significantly smoother than glazed surface. SEM photomicrographs was compatible with the mean Ra values. The highest mean VHN value was measured on the porcelain surface achieved polishing. Mean VHN value for porcelain surface polished after glazing was not significantly different from that of unglazed surface.