Prior to final cementation, ceramic restorations may require minor adjustments using rotary instruments. The use of these instruments on highly polished and glazed ceramic surfaces results in roughness. A study by Ghazal and Kern published in the May issue of the Journal of Prosthetic Dentistry evaluated the relationship between wear of enamel as well as nanofilled composite resin when opposing the surface roughness of ceramic material. Three sets of zirconia ceramic balls with different amounts of surface rougness were tested in vitro against 3 groups of 8 human teeth each (enamel) and 3 groups of 8 nanofilled composite resin teeth, using a mastication simulator. Volume loss and depth of wear of the enamel and resin were measured using a laser scanner. It was found that a significant increase in wear of both enamel and composite resin occurred as the roughness of the opposing ceramic increased. The enamel showed less wear than the nanofilled composite resin. Eliminating surface roughness has other clinical implications. An irregular surface results in increased retention of plaque, intraoral irritation, and possibly a decrease in aesthetics. The ceramic roughness should be highly polished before cementing any restoration. The study concludes that irregular, roughened ceramics will wear human enamel and nanofilled composite restorations at a different rate. After adjusting any ceramic restoration, it must be highly polished.
(Source: Oakstone Review, June 30, 2009)
