In vitro Surface Roughness of Novel Lithium Silicate CAD/CAM Material

Objectives: This in-vitro study evaluated the surface roughness of a novel, fully crystalized, Lithium Silicate CAD/CAM ceramic (GC Initial LiSi, GC America) using three different surface finish techniques for chairside applications.
Methods: A full coverage onlay was designed and milled using GC Initial LiSi on a CAD/CAM system (CEREC Omnicam SV 4.6 and MCX mill, Dentsply Sirona) in order to produce a flat intaglio surface. One calibrated operator polished/glazed the flat surface of 60 samples. Four groups of 15 samples (N=45) were either left untreated (baseline); polished with a rubber wheel (DPO03 Meisinger USA) and LS spiral polishers (Meisinger USA) followed by Diapolisher paste (GC America); glazed (GC Luster Paste NF Neutral, GC America) or polished with Diapolisher paste after glazing. 3D surface roughness arithmetical mean height values (Sa) were assessed using a confocal laser microscope (Lext OLS4000, Olympus).
Results: Analysis of variance revealed a statistically significant difference in mean 3D surface roughness values (Sa) among surface finish techniques. Tukey multiple comparisons showed that all pairwise comparisons were statistically significantly different at 95% confidence level.
Conclusions: All surface finish techniques produced samples significantly smoother than baseline Sa values for GC Initial LiSi. Polishing with rubber wheel/spiral polishers followed by polishing with Diapolisher paste, provided the lowest surface roughness values, which were significantly smoother than GC Luster Paste NF Neutral glazed values. Samples that were polished after glaze were significantly smoother that when glaze was evaluated alone. This study was funded by a research grant from GC America.