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Surface roughness of zirconia for full-contour crowns after clinically simulated grinding and polishing

2014; Springer Nature; Volume: 6; Issue: 4 Linguagem: Inglês

10.1038/ijos.2014.34

2049-3169

Rim Hmaidouch, Wolf‐Dieter Müller, Hans‐Christoph Lauer, Paul Weigl,

Orthodontics and Dentofacial Orthopedics

The aim of this study was to evaluate the effect of controlled intraoral grinding and polishing on the roughness of full-contour zirconia compared to classical veneered zirconia. Thirty bar-shaped zirconia specimens were fabricated and divided into two groups (n=15). Fifteen specimens (group 1) were glazed and 15 specimens (group 2) were veneered with feldspathic ceramic and then glazed. Prior to grinding, maximum roughness depth (Rmax) values were measured using a profilometer, 5 times per specimen. Simulated clinical grinding and polishing were performed on the specimens under water coolant for 15 s and 2 N pressure. For grinding, NTI diamonds burs with grain sizes of 20 µm, 10 µm, and 7.5 µm were used sequentially. The ground surfaces were polished using NTI kits with coarse, medium and fine polishers. After each step, Rmax values were determined. Differences between groups were examined using one-way analysis of variance (ANOVA). The roughness of group 1 was significantly lower than that of group 2. The roughness increased significantly after coarse grinding in both groups. The results after glazing were similar to those obtained after fine grinding for non-veneered zirconia. However, fine-ground veneered zirconia had significantly higher roughness than venerred, glazed zirconia. No significant difference was found between fine-polished and glazed zirconia, but after the fine polishing of veneered zirconia, the roughness was significantly higher than after glazing. It can be concluded that for full-contour zirconia, fewer defects and lower roughness values resulted after grinding and polishing compared to veneered zirconia. After polishing zirconia, lower roughness values were achieved compared to glazing; more interesting was that the grinding of glazed zirconia using the NTI three-step system could deliver smooth surfaces comparable to untreated glazed zirconia surfaces. Non-veneered zirconia crowns respond well to clinical polishing leaving a smooth finish to help combat decay, research from Germany states. Zirconia (zirconium oxide) is a high-strength material commonly used for all-ceramic tooth restoration. Zirconia crowns are often veneered with dental porcelain but the veneer is prone to chipping, particularly during the clinical polishing and grinding carried out after dental restoration procedures. The resulting rough surfaces can wear down opposing teeth and attract plaque. Rim Hmaidouch and co-workers at the Johann Wolfgang Goethe University in Frankfurt tested the effect of polishing and grinding on zirconia crowns with and without veneers, aiming to find the best quality finish. They found that, after grinding and polishing procedures, glazed zirconia with no porcelain veneer had fewer defects and less surface roughness than veneered zirconia.