Evaluation of color stability and surface properties of different CAD/CAM materials

As the use of developing CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) technologies in dentistry increases, new generation materials have begun to be developed. One of the goals of these developed materials is to provide single-visit chairside restoration production. The aim of this study was to investigate changes in color, surface roughness, surface hardness, and contact angle of three different resin matrix ceramics and one fully crystallized lithium disilicate ceramic, all designed for use in CAD/CAM systems without the need for post-milling firing. A total of 120 samples, each 1,5 mm thick, were obtained from Vita Enamic (VITA Zahnfabrik, Bad Säckingen, Germany), Cerasmart270 (GC, Tokyo, Japan), Shofu Block HC (Shofu, Kyoto, Japan), and GC Initial LiSi (GC, Tokyo, Japan) blocks (n=30 per material). The samples were polished with special mechanical polishing sets, then divided into three subgroups to be immersed in either distilled water, coffee and wine (n=10 per subgroup). The samples were stored in an oven at 37°C for 30 days. Color measurements were taken initially and at days 7, 14, and 30 using a spectrophotometer (Vita EasyShade V, Vita Zahnfabrik, Germany) on a white background in a D65 light source color measurement box. The color difference was calculated using the CIEDE2000 formula. Surface roughness and hardness values were measured initially and after 30 days, and three random samples from each group were selected to record initial and 30-day contact angle values. Data were analyzed with IBM SPSS v23.0. Normal distribution conformity was assessed with the Shapiro-Wilk test, and group differences for normally distributed parameters were evaluated with a one-way ANOVA test. Mean comparisons across materials and solutions were done with a two-way ANOVA, and multiple comparisons were assessed with Tukey's test. Changes over time within each group were determined using repeated-measures ANOVA, with Tukey's test for post hoc analysis. A significance level of p<0.05 was used. At the end of 30 days, the highest discoloration was seen in the SH-Wine group, while the LiSi-Distilled water group showed the lowest discoloration. Material type, solution type, and time were found to have a significant effect on discoloration (p<0.05). The highest surface roughness was observed in the LiSi-wine and coffee groups after 30 days. The LiSi-Distilled water group showed the least decrease in surface hardness, while the VE-Wine group showed the most significant decrease. When examining contact angle values, the highest change was observed in the LiSi-Wine group. In conclusion, lithium disilicate ceramics demonstrated better color stability than resin matrix ceramics under the conditions of this study, and solution type, time, and material type significantly impacted surface hardness, roughness and contact angle. Keywords: CAD/CAM, Resin ceramic, Lithium disilicate ceramic, Color stability, Surface roughness, Microhardness, Contact angle