Statement of problem: Monolithic zirconium restoration is widely used in dental practice. Several sintering processes have been employed and it may affect the color coordinates of monolithic zirconium restorations which is crucial for a successful esthetic restoration.
Purpose of the study: to evaluate the effect of different sintering techniques on the color parameters of zirconium ceramic restorations.
Materials & Methods: Thirty specimens were milled from Zenostar Translucent zirconia, shade T2 using Kavo Everest engine milling machine (KaVo Dental, Charlotte, NC, USA). The final dimensions of the discs were 10 mm diameter x 2 mm thickness. They were divided into three groups according to the sintering process, ten discs each. Group I: Microwave Sintering (MS), Group II: Speed Sintering (SS), & Group III conventional Sintering (CS). The spectrophotometer (Easyshade V, VITA Zahnfabrik GmbH, Bad Sackigen, Germany) was recalibrated according to the manufacturer's recommendation. During the color measurements, the specimens were placed on a gray background and the L, a, and b values were recorded. The difference in color (∆E) was calculated through differences in the color parameters using the following equation: *=[(L1*-L0*)2+(a1*-a0*)2+(b1*-b0*)2]1/2
Results: there was a statistically significant difference in ΔE between the tested groups. The lowest value was recorded for CS and MS groups. On comparing to the classical vita shade tabs, ΔE values for the studied groups was in the acceptable value except when compared to C1 and B2 shade tabs.
Conclusions: The sintering process affected the optical and color parameters of zirconium specimens especially for SS group.