Effect of changes in sintering parameters on monolithic translucent zirconia

Objectives. Aim of this study was to evaluate the effect of different sintering parameters on color reproduction, translucency and biaxial flexural strength of monolithic zirconia. Methods. Translucent zirconia discs having 15 mm diameter, 1 mm thickness, and shade A3 were milled and divided according to the sintering temperatures (1460 degrees C, 1530 degrees C, and 1600 degrees C) into three groups (n = 30). Each group was later divided into three subgroups (n = 10) according to the sintering holding time (1, 2, and 4 h). Easyshade spectrophotometer (Vita, Bad Sackingen, Germany) was used to obtain the Delta E between the specimens and the shade A3. Mean Delta E values below 3.0 were considered clinically imperceptible, Delta E values between 3.0 and 5.0 were considered clinically acceptable and Delta E values above 5.0 were considered clinically unacceptable. Contrast ratio (CR) was obtained after comparing the reflectance of light through the specimens over black and white background. Biaxial flexural strength was tested using the piston-on-three balls technique in a universal testing machine. Results. Mean Delta E results ranged from 4.4 to 2.2. Statistically significant decrease in the Delta E was observed as the sintering time and temperature increased. CR decreased from 0.75 to 0.68 as the sintering time and temperature increased. No significant change in the biaxial flexural strength was observed. Signcance. Sintering zirconia using long cycles and high temperatures will result in reduction of Delta E and CR. Biaxial flexural strength is not affected by changes in the evaluated sintering parameters. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.