Profilometer evaluation of the effect of various polishing methods on the surface roughness in dental ceramics of different structures subjected to repeated firings

Objective: To evaluate the changes in surface roughness of dental ceramics with various substances/ instruments and polishing methods during the course of repeated firings. Method and Materials: Three types of dental ceramic (IPS Classic, Empress Esthetic, and Empress 2 [all by Ivoclar Vivadent]) were used to form three groups, respectively. The samples from the first group were subjected to glaze, the second group to natural glaze, and the third group to mechanical polishing. As many as seven firings were performed on each sample, and surface roughness measurements of the samples were carried out at certain stages. Statistical evaluation was performed through repeated-measures ANOVA, and the Duncan test proved that the differences among the mean values were by no means a coincidence. Results: The interaction among the substrates, the method used, and the time was statistically significant (P .05). Mechanical polishing significantly increased surface roughness (P .05), and the greater number of firings significantly decreased the amount of surface roughness (P .05). Conclusion: In terms of surface roughness, the best method available is the glaze method and the best material is IPS Classic. The mechanical polishing process generates rough surfaces. Repeated firings should be avoided as much as possible because they have a destructive effect on the glaze layer and deform the surface. Keywords: dental ceramic, polishing methods, repeated firings, surface roughness