Effects of Six Surface Treatment Methods on the Surface Roughness of a Low-Fusing and an Ultra Low-Fusing Feldspathic Ceramic Material

Purpose: The purpose of this in vitro study was to determine the effects of six surface treatment methods on the surface roughness of two feldspathic ceramic materials.
Materials and Methods: One hundred twenty metal discs were cast (Remanium CS). A low-fusing feldspathic ceramic (Vita Omega 900) was fired onto 60 metal discs, and an ultra low-fusing feldspathic ceramic (Finesse) was fired onto the other 60 metal discs. Six surface treatment methods were selected: (1) autoglazing (AUG), (2) overglazing (OVG), (3) polishing (POL), (4) fine diamond disc grinding + polishing + autoglazing (FDPA), (5) coarse diamond disc grinding + polishing + autoglazing (CDPA), (6) polishing + autoglazing (PA). Omega specimens were assigned to six experimental groups representing six surface treatment methods (Om-AUG, Om-OVG, Om-POL, Om-FDPA, Om-CDPA, Om-PA) (n = 10). Finesse specimens were also assigned to six experimental groups (Fn-AUG, Fn-OVG, Fn-POL, Fn-FDPA, Fn-CDPA, Fn-PA) (n = 10). Treated ceramic surfaces were examined by means of profilometry and transmission electron microscopy.
Results: In Omega groups mean roughness values ranged as follows: group Om-AUG = Om-POL > Om-OVG > Om-CDPA = Om-FDPA > Om-PA ( p < 0.001). No significant difference was found between groups Om-AUG/Om-POL and Om-CDPA/Om-FDPA ( p > 0.05). In Finesse groups mean roughness values ranged as follows: Fn-CDPA > Fn-FDPA = Fn-AUG = Fn-POL = Fn-OVG > Fn-PA ( p < 0.001). No significant difference was found between Fn-FDPA, Fn-AUG, Fn- POL and Fn-OVG ( p > 0.05).
Conclusions: For both ceramic types, the smoothest surfaces were obtained with polishing prior to autoglazing. Diamond disc grinding prior to polishing and autoglazing (Fn-FDPA, Fn-CDPA) displayed the roughest surfaces in ultra low-fusing ceramic (Finesse). Autoglazing alone and polishing displayed the roughest surfaces in low-fusing ceramic material (Om-AUG, Om-POL).