The Effect of a Polishing Protocol on the Surface Roughness of Zirconium Oxide.

PURPOSE: To evaluate the surface roughness values of zirconium oxide samples that were gradually polished using a commercially available polishing system and polishing paste. MATERIALS AND METHODS: A total of 50 rectangular specimens of predetermined size (10 x 10 x 3 mm) were sintered from zirconium oxide. Samples were randomly assigned to one of five groups (n = 10 each): control, coarse (Co), fine (F), super fine (SF), or polishing paste (PP). In the control group, no polishing was done; in the Co group, a coarse polisher was used; and the specimens in the remaining three groups underwent additional processing with a fine rubber abrasive. For SF and PP samples, subsequent treatment with a super fine polisher was applied. Finally, for the PP group, a goat-hair brush with diamond polishing paste was used. An optical profilometer was used to evaluate roughness average (Ra) in micrometers (mum). ANOVA and Games-Howell post hoc tests were utilized to detect differences between groups. The significance level was set to alpha = .05. RESULTS: Surface roughness gradually decreased with further polishing throughout the groups: control Ra = 0.525 +/- 0.099 mum; Co Ra = 0.252 +/- 0.038 mum; F Ra = 0.196 +/- 0.035 mum; SF Ra = 0.114 +/- 0.031 mum; and PP Ra = 0.054 +/- 0.020 mum. Statistically significant differences were detected among all groups (P < .05). CONCLUSION: A surface roughness of 0.054 mum can be achieved if a full zirconia polishing protocol is used. Zirconium oxide can be polished to various surface roughnesses using commercially available polishing products.