Evaluation of the optical and surface properties of monolithic CAD-CAM ceramics after simulated tooth-brushing

Monolithic computer-aided design and computer-aided manufacturing (CAD-CAM) ceramics have various microstructures, but studies on their optical and surface properties after tooth-brushing are lacking.

The purpose of this in vitro study was to evaluate the changes in the color, gloss, surface roughness, and surface topography of different monolithic CAD-CAM ceramics after simulated tooth-brushing and compare the tested parameters of the different ceramics.

Ninety specimens were prepared with a 1.5-mm thickness from 9 different materials: monolithic zirconia (ZR), lithium disilicate ceramics (precrystallized and crystallized), zirconia reinforced lithium silicate ceramics (precrystallized and crystallized), interpenetrating network ceramic, leucite reinforced ceramic, feldspathic ceramic, and interpenetrating network nanoceramics (n=10). After mechanical polishing, the color parameters, gloss, and surface roughness values of each specimen were measured. Then, the specimens were subjected to 50 000 tooth-brushing cycles. After the brushing simulation, the color change (ΔE₀₀) values were calculated, and the gloss and surface roughness values of the specimens were measured. Data were statistically analyzed with 2-way repeated measures of ANOVA and Bonferroni multiple comparison tests (α=.05).

The brushing simulation and ceramic type affected the gloss and surface roughness values of the tested ceramics (P<.001). The surface roughness values of the ceramics increased after 50 000 cycles of simulated brushing. The surface gloss of the ZR group significantly increased after 50 000 cycles of simulated brushing (P<.001). Only the ceramic type affected the color change values (P<.001). The color change value (ΔE₀₀) of ZR was the highest among the tested materials, exceeding the perceptibility threshold after 50 000 cycles, while the ΔE₀₀ of the other materials was lower.

Simulated tooth-brushing affected the surface gloss and surface roughness of the tested materials. The ceramic type affected the surface gloss, surface roughness, and color change values. Except for the monolithic zirconia, the color change values were below the perceptibility threshold (0.8) in the experimental groups.