THREE-BODY WEAR POTENTIAL OF DENTAL YTTRIUM-STABILIZED ZIRCONIA CERAMIC AFTER GRINDING, POLISHING, AND GLAZING TREATMENTS

Statement of problem. Zirconia complete-coverage crowns are being widely used as restorations because of their improved esthetic characteristics. Data about the enamel wear potential of this ceramic after chair side adjustments are sparse. Purpose. The purpose of this study was to investigate the 3-body wear of enamel opposing 3 types of ceramic (dense sintered yttrium-stabilized zirconia; Crystal Zirconia; DLMS) (Z), a lithium disilicate (IPS e-max CAD; Ivoclar Vivadent) (E), and a conventional low-fusing feldspathic porcelain (VitaVMK-Master; Vita Zahnfabrik) (P), treated to impart a rough, smooth, or glazed surface. Material and methods. Twenty-four specimens of each of the zirconia and the lithium disilicate ceramic were sectioned from computer-aided design and computer-aided manufacturing blocks into rectangular plates (15x12x2 mm). Twenty-four specimens of the feldspathic porcelain were formed into disks (12 mm diameter) from powders compressed in a silicone mold. All specimens (n=72) were prepared according to the manufacturers' recommendations. Specimens of each ceramic group were placed into 1 of 3 groups: group R, rough surface finish; group 5, smooth surface finish; and group G, glazed surface finish. A total of 9 groups with 8 specimens each were placed in a 3-body wear simulator, with standardized enamel specimens (n=72) acting as the substrate. The wear of the enamel specimens was evaluated after 50 000 cycles. The data were analyzed with 2-way ANOVA and the Tukey HSD multiple comparison test (alpha=.05). Results. The data showed that the smooth zirconia group (ZS) was associated with the least amount of enamel wear (1.26 +/- 0.55 mm(2)). The most antagonistic enamel wear was associated with the glazed groups ZG (5.58 +/- 0.66 mm(2)), EG (3.29 +/- 1.29 mm(2)), and PG (4.2 +/- 1.27 mm(2)). Conclusions. The degree of enamel wear associated with monolithic zirconia was similar to conventional feldspathic porcelain. Smoothly polished ceramic surfaces resulted in less wear of antagonistic enamel than glazing.