Effect of glazing on translucency, color, and surface roughness of monolithic zirconia materials.

OBJECTIVES: To assess the effect of material, thickness and glazing upon the color, translucency, and roughness of monolithic zirconia. MATERIALS AND METHODS: Sixty discs (0.8, 1.5, and 2 mm thickness) were fabricated from A1 translucent zirconia (IPS e.max ZirCAD/MT, Katana/HT, Vita YZ/HT, Cercon/HT) and glazed. Roughness (Ra) was assessed with a profilometer and color coordinates were measured with a spectrophotometer on a black, white, and tooth-shaded background before and after glazing. Relative translucency parameter (RTP), color differences (CIEDE2000) and differences in translucencies between materials, before and after glazing were calculated. RTP, Ra, color differences were statistically analyzed using ANOVA. Any significant interaction between factors was further analyzed using Tukey's HSD. RESULTS: RTP values were significantly different between materials (P < .001) and thicknesses (P < .001), with the interaction effect between material type and thickness, also significant (P < .001). However, glazing did not have a significant effect on RTP values (P = .782). Color differences resulted after glazing were significantly different between materials (P < .001), and thicknesses (P < .001) with the interaction effect also significant (P < .001). Glazing influenced roughness, Ra decreasing for all materials (P < .001). CONCLUSIONS: As a result of glazing, only color changes were statistically significant. Translucency varied among brands of precolored monolithic zirconia; the differences increased for greater thicknesses. CLINICAL SIGNIFICANCE: Glazing is an important step in the technological process of ceramic restorations; however, it can influence the final optical appearance of the restoration as color changes could be expected after the application of the glaze.

Translucency and masking properties of two ceramic materials for heat-press technology.

OBJECTIVES: To assess the translucency of two pressable ceramics and to analyze their masking property when placed on different tooth-shaded backgrounds. MATERIALS AND METHODS: Thirty discs (1-mm thickness) were fabricated using two pressable ceramics (shade/translucency): 1M1T/HT, 1M2T/HT, 2M2T (VITA PM9), and A1LT/HT, B1LT/HT, A2LT (e.max Press). Color measurements of discs were performed with a dental spectrophotometer on tooth-colored backgrounds (A1/A2/A3/A3.5/A4), and black and white backings. The masking property was calculated as the color difference (CIEDE2000) between parameters of discs on control (A1, A2) and test backgrounds (A3, A3.5, A4). One-way ANOVA was used for assessing differences in translucency parameter (TP) between ceramics. Two-way ANOVA was used for detecting differences among groups when measured over tooth-shaded backgrounds (α = 0.05, Bonferroni correction). RESULTS: TP ranged between 14.96 (B1LT) and 25.18 (1M1HT). A significant difference in TP was found between tested ceramics (F = 949.949, P < .001). However, TP did not vary significantly between 1M1HT and 1M2HT (P > .05), 1M1T, A1HT and B1HT (P > .05), 1M2T, 2M2T, and A2HT (P > .05). A significant interaction effect of underlying background on color of ceramic discs was found (F = 107.994, P < .001). CONCLUSION: VITA PM9 demonstrated higher translucency than e.max Press ceramics. Except A1LT, all ceramic materials evaluated showed poor masking properties on A4 background. CLINICAL SIGNIFICANCE: Highly translucent ceramics should be wisely used for restoring the appearance of dental structures since background color has a large effect upon these materials. The more recently introduced pressable ceramics showed high levels of translucency.