Comparative Study of the Effectiveness of Laboratory-Formulated Polishing Pastes for Two CAD/CAM Ceramic Restorative Materials

Purpose To evaluate the effect of different polishing pastes with different particle sizes on the surface finish of two different CAD/CAM ceramics. Materials and Methods A total of 128 specimens were prepared of two CAD/CAM ceramics: lithium disilicate (12.4 x 14.5 x 2 mm) and monolithic zirconia (17.5 x 12.5 x 2.5 mm). They were divided randomly into 8 groups according to surface treatment (n = 8). Group 1 (control) was left as received after crystallization or sintering with no further surface treatment; Group 2 (glazed); Group 3 (positive control), where specimens were polished using standardized surface treatment (medium grit silicon carbide discs, rubber cup and pumice slurry, then rubber cup and toothpaste). For groups 4 to 8, in addition to silicon carbide and pumice slurry polishing, specimens were further polished using a diamond paste (DP), and polishing pastes of microzirconia (MZ), nanosilica (NS), nanodiamond (ND), and nanozirconia (NZ), respectively. Surface roughness (R-a) was measured using noncontact profilometer. The mean values were compared using ANOVA and Post Hoc Tukey's test (alpha = 0.05). Specimens' surfaces were studied using a scanning electron microscope (SEM). Results Positive control group and MZ exhibited significant R-a of lithium disilicate compared to control (p < 0.001), glazed (p = 0.001), DPs (p = 0.002), NS (p < 0.001), ND (p < 0.001), and NZ (p = 0.002). In the case of zirconia, positive control showed a significantly higher R-a compared to all other groups (p < 0.001). No statistical difference was found between all other polishing techniques (positive control, glazed, DPs, NS, ND, MZ, and NZ) (p > 0.05). Conclusion Polishing with ND, NZ, and NS lab-formulated pastes produced surfaces with comparable smoothness to control and glazed specimens for lithium disilicate and zirconia ceramic materials.