Sensitivity of Porcelain Translucency to Powder-Liquid Mixing Ratio

Consistent translucency is desirable for predictable esthetics. Previous researchers found some porcelain to be "technique sensitive" in that varying powder slurry consistency increased variability of porosity and strength. Objective: The objective of this study was to investigate the effect of powder-liquid mixing ratio on the translucency of dental porcelain. Methods: Two body porcelains (Duceram LFC and Eris) and two corresponding veneer porcelains were mixed with deionized water. For each specimen, 1.000 g of porcelain powder was mixed with water to form a slurry with ideal consistency. Two additional groups of specimens were made from each porcelain by varying the powder-liquid ratio (+0.28 g/mL and -0.22 g/mL from ideal). The slurries were condensed in a plastic syringe, fired, and polished to a 3 mm finish to form 48 disk-shaped specimens (14 mm diameter, 1.10 mm thickness). Each specimen was coupled to standard ceramic tiles using a liquid with a refractive index of 1.5000, and the color shade was measured in CIE L*a*b* coordinates using a tristimulus colorimeter. Translucency was assessed by calculating the contrast ratio of shade value (L*) in front of black vs. white backgrounds. Results: Mean contrast ratio values (standard deviations) were: