Effect of glazing or mechanical polishing surface treatments on color stability of two types of CAD/CAM ceramics

Abstract

Abstract

Introduction: Similar to natural human teeth, dental ceramics are also effected by different bevarages in intraoral inviroment Which may lead to color changes. The effects of different surface treatments on the color of a recently introduced CAD/CAM monolithic ceramic are unknown. The purpose of this study is to investigate the color stability of CAD/CAM Lithium disilicate ceramic and CAD/CAM zirconia-reinforced lithium silicate ceramic, which were prepared with various surface treatments incuding glazing or mechanical polishing, following 2-weeks storage in coffee solution.

Materials and methods: In this experimental study, 20 rectangular specimens was sectioned from ZLS and LDS blocks into 1.5×7×12 mm dimentions and in A2 color (ZLS, n=10) and (LDS, n=10) ZLS (Zirconia-reinforced lithium silicate) (Celtra Duo, Dentsply) LDS (Lithium Disilicate glass-ceramic) (IPS e.max CAD, Ivoclar Vivadent AG) After ultrasonic cleaning and firing of the specimens, they were finished and polished in two groups. Specimens in the first group were polished using a polishing kit and the second group specimens were glazed and heated in a porcelain firing oven (according to the manufacture’s instructions ZLS will be fired at 820˚C for 60 seconds and LDS will be fired at 770˚C for 90 seconds). Then the specimens were immersed in coffee for two weeks, the color cordinates of specimens were measured using spectrophotometer before and after immersion in coffee. L, a, b parameters were used to measure color values . the color variation between the initial measurments and the measurments after immersion in coffee was calculated. Statistical analysis was conducted using paired samples t test and independent samples t test. color changes were calculated and statistically analyzed using ANOVA test (two way). level of significance was set at p<0.05 SPSS software version 25 was used for statistical analysis. Results: Material type had a significant effect on color differerence (p-value<0.001), in both glazing and mechanical polishing groups Lithium Disilicate glass-ceramic showed statistically lower color changes with respect to Zirconia-reinforced lithium silicate. in both materials, glaze procedure showed statistically lower color change values than mechanical polishing (p-value<0.001). all color difference values of all materials were smaller than the clinical acceptability thereshold (ΔΕ<3.3). Conclusions: Different surface treatments of CAD-CAM monolithic zirconia-reinforced lithium silicate and lithium disilicate glass-ceramics resulted in clinically acceptable color changes. Glazing led to more color stability with respect to mechanical polishing for zirconia‐reinforced lithium silicate and lithium disilicate glass‐ceramic. Lithium disilicate glass‐ceramic showed higher color stability compared to zirconia‐reinforced lithium silicate ceramic.