Effects of immersion in various beverages, polishing and bleaching systems on surface roughness and microhardness of CAD/CAM restorative materials.

Background: The aim of this study was to investigate the effect of an immune-boosting beverage with Sambucus nigra (SAM), an energy beverage (ENE), an in-office bleaching agent with a novel composition, and a fine-grain professional dental prophylaxis (PDP) paste on the surface roughness (Ra) and microhardness (MH) of CAD/CAM restorative materials over time.

Methods: Feldspathic ceramic (FC) and polymer infiltrated ceramic network (PICN) specimens were prepared (N = 126). Glazing, polishing, bleaching and immersion in beverages groups were formed. Bleaching gel containing 25% Hydrogen Peroxide Superior was applied to the specimens with a bleaching pen. Ra and MH were measured at five time points of baseline, days 1, 14, 28 and after PDP. Scanning electron microscopy (SEM) images were taken after PDP. Statistics were performed by ANOVA and Bonferroni tests (α = 0.05).

Results: Ra increased over time regardless of material type, polishing method, beverage type and bleaching (p < 0.0001). Glazed and polished FCs caused higher roughness than PICN, SAM and ENE than distilled water, and bleaching than no bleaching (p < 0.0001). For glazed or polished FCs, MH decreased slightly lower at all time points, but for PICN, MH increased until day 28, not changing after PDP. Beverages decreased the MH of ceramics at all time points, but PDP did not lead to a change for PICN (p < 0.0001). The MH decreased more in bleached specimens than in non-bleached specimens up to day 28 (p < 0.0001). According to the SEM images after PDP, the glazed FC had numerous crack marks, pores and detached particles. The polished FC had traces of mechanical polishing. The polymer part of the PICN had voids, but the ceramic part was better preserved.

Conclusions: Both energy beverages and immune-boosting beverages can increase roughness on FCs compared to PICNs. There was no significant difference between glazing and polishing in terms of lower roughness in FCs. PDP tended to slightly increase the roughness for ceramics, while it tended not to change it for PICN. Beverages decreased the microhardness of ceramics. PDP further decreased the microhardness in glazed ceramics, but increased it in polished ones. In PICN the microhardness increased over time, but decreased slightly after PDP.