Investigation of color properties/stability of different CAD/CAM ceramic materials after aging process

The aim of this study is to examine the color changes of different CAD/CAM ceramic materials after aging with thermal cycle and keeping in coffee solution. Three CAD/CAM ceramic blocks, which are lithium disilicate reinforced glass ceramic (IPS e.max CAD), zirconia reinforced lithium silicate ceramic (Vita Suprinity) and hybrid nano ceramic (Cerasmart), were used in our study. A total of 180 samples were prepared by taking 2 mm thick sections from ceramic blocks with HT translucency value in A2 color (n=10). Three different surface treatments were applied to each material. Glaze was applied to 60 samples, 60 samples were mechanically polished, 60 samples were determined as the control group and no surface treatment was performed. Samples were grouped so that n=10. After the surface treatments, the samples were divided into two groups, one group was aged by thermal cycle, and the other group was kept in coffee solution for 15 days and color measurements were made on the 1st, 3rd, 7th and 15th days. Color evaluations were made using the Vita Easyshade Advance V (VITA Zahnfabrik, Bad Sackingen, Germany) spectrophotometer device according to the CIE L*a*b* color system. In this study, the normality distribution assumption for the continuous variables of the obtained data was investigated with the Kolmogorov-Smirnow test and the homogeneity was investigated with the Levene test. Two-Way ANOVA and One Way ANOVA test analyzes were used in the comparison of the differences between the means of the groups, considering the parametric analysis test conditions. According to the results of the study, aging with thermal cycle and keeping in coffee solution caused color change in all materials. There is a statistically significant difference between the materials in terms of color change (p<0.001). There was no significant difference between the surface treatments in the thermal aging groups (p=0.57). IPS e.max CAD was the ceramic material with the least color change among all groups. The color change values of all ceramic groups increase depending on time in the samples kept in the coffee solution. In terms of color stability, mechanical polishing can be recommended as an alternative to glazing for IPS e.max CAD and Vita Suprinity material. Mechanical polishing can be recommended for Cerasmart material. Keywords: Color stability, Aging, All ceramics, CAD/CAM