A Comparison of Surface Roughness and Gloss of CAD/CAM Blocks

Objectives: The purpose of this study is to evaluate polishing modalities for three commonly used materials in CAD/CAM restorations: nano-ceramic resin (NR), feldspathic porcelain (FP), and lithium disilicate (LD) blocks. This data will give clinicians insight as to which of the tested material will produce the best surface finish, and by what method to achieve that finish.
Methods: All blocks were cut into slices and roughened with a diamond bur to provide a uniform baseline. Gloss and surface roughness measurements were taken with a gloss meter and a profilometer. The FP samples were hand-polished on one side with ceramic polishers, and were glazed on the other side. The NR samples were hand-polished on one side with composite polishers, and an unfilled-resin sealer was applied and photo-polymerized on the other side. The lithium disilicate blocks were glazed and crystalized in an oven. Final gloss and surface roughness measurements were taken. A paired t-test was used to compare before and after data from each experimental group. 1-way ANOVA followed by Newman-Keuls Multiple Comparison tests were used to statistically analyze the variance of gloss and surface roughness results (P<0.05).

Results: There was a significant difference in gloss between the following groups: polished NR and glazed FP, polished NR and surface-sealed NR, and between polished NR and polished FP. This test also indicated significant differences in surface roughness between all of the experimental groups except: polished FP and polished NR, polished NR and surface-sealed NR, surface-sealed NR and LD. The results indicate that the hand-polished FP group had the highest gloss values. The hand-polished FP also had the lowest surface roughness values.
Conclusions: Hand-polished FP blocks gave the best surface finish, both in terms of gloss and roughness. This study provides useful data for the practitioner seeking predictable and esthetic finishes in his/her CAD/CAM restorations.