Effect of surface treatments on optical, topographical and mechanical properties of CAD/CAM reinforced lithium silicate glass ceramics

Objectives: To investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC's) and their combined effect on the output of a light curing unit (LCU). Methods: Four CAD/CAM LSC's were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinforced silicates (Vita Suprinity; VS and Celtra Duo;CD) and Lithium Aluminum Disilicate (CEREC Tessera; CT). Ceramic specimens (n = 240) were divided into six subgroups according to their surface treatment: (a) Control, (b) Hydrofluoric acid (HF) 5%, (c) HF 5% + Neutralizing agent (N), (d) HF 9%, (e) HF 9% +N and (f) Self-etching ceramic primer (SEP). Irradiance, power and radiant exposure of a LCU were measured with MARC-LC following ceramic specimen interposition. Direct light transmission (T%) and absorbance (Abs%) of the specimens were measured with UV-Vis spectrophotometry. Roughness (Sa, Sq) and wettability (theta degrees) were measured with optical profilometry and sessile drop profile analysis, respectively. Biaxial flexural strength (sigma) of the ceramic specimens was measured by the ball-on-three-balls method and ceramic specimens were examined microscopically. Statistical analyses was performed by two-way ANOVA followed by post hoc multiple comparisons (alpha = 0.05). Results: Acid neutralization decreased T% and increased Abs% in all LSC's and highest T% was exhibited with VS. Neutralized EC, VS and CD displayed higher Sa in HF9, while neutralized CT displayed higher Sa in HF5. Self-etch primer significantly reduced theta degrees (p < 0.001). sigma was observed in the followed ascending order: HF9 +N < HF9 < HF5 +N < HF5 < SEP < Control for all LSC's. Significance: Optical, topographical and mechanical properties of the CAD/CAM ceramic blocks were strongly dependent on the type of surface treatment. Results of neutralization post-etching indicate promising potential for future investigations.