Influence of the finishing technique on surface roughness of dental porcelains with different microstructures

This study compared the surface roughness of 4 dental porcelains with different microstructures (d.Sign-D, Finesse-F, Noritake-N and Symbio-S) using varied surface treatments. The porcelain surfaces were submitted to the following surface treatments: 1) g (glazing only); 2) rg (polishing with a rubber wheel before glazing); 3) 2g (reglazing); 4) r (rubber wheels); 5) rp (rubber wheels + diamond paste); 6) d (sandpaper discs) and 7) dp (sandpaper discs + diamond paste). Treatments 3 through 7 were performed after breaking the glaze layer with a diamond bur. Surface roughness (Ra, in m) was determined using a profilometer (n=10). Visual inspection was made using the scanning electron microscope. Microstructural characterization was also performed (hardness, leucite content and particle size). Reglazed specimens presented significantly rougher surfaces compared to glazed specimens. The use of a polishing paste after the sandpaper discs or after the rubber wheel resulted in a reduction of the Ra value for all materials (except for the dp group of porcelain S). Rubber or discs followed by diamond paste were the best surface treatments for porcelains D (D-rp: 0.21 +/- 0.06 microm and D-dp: 0.22 +/- 0.05 microm) and F (F-rp and F-dp: 0.17 +/- 0.03 microm). For porcelains N and S, both reglazing (2g) and the use of rubber or sandpa- per discs followed by diamond paste (groups rp and dp) resulted in similar roughness (N-2g: 0.22 +/- 0.03 microm; N-rp: 0.22 +/- 0.04 microm; N-dp: 0.20 +/- 0.04 microm, S-2g: 0.22 +/- 0.04 microm; S-rp: 0.19 +/- 0.04 microm; S-dp: 0.23 +/- 0.04 microm).

The best choice of surface treatment for leucite-based porcelains depended on the material considered. Porcelains with lower leucite content (F and S) tended to present lower roughness compared to those with higher leucite content after being polished with rubbers or discs followed by diamond pastes.