The effect of staining and vacuum sintering on optical and mechanical properties of partially and fully stabilized monolithic zirconia.

The effect of staining and vacuum sintering on optical properties and the bi-axial flexural strength of partially and fully stabilized monolithic zirconia (PSZ, FSZ) were evaluated. Disc-shaped specimens divided into three subgroups (n=15): non-stained, stained and non-stained with vacuum sintering. After staining and sintering, optical properties were evaluated using a reflection spectrophotometer and bi-axial flexural strength was tested using the piston-on-three balls technique. Statistical analysis was performed using multivariate analysis of variance (MANOVA) followed by post-hoc Tukey's tests (p<0.05). Staining decreased translucency parameter (TP) values of FSZ (p<0.05). Sintering under vacuum enhanced TP values for PSZ (p<0.05). Staining enhanced surface gloss for both types of zirconia (p<0.05). Staining increased bi-axial flexural strength of FSZ (p<0.05), while it decreased the strength of PSZ (p<0.05). Sintering under vacuum provided minimal benefits with either type of zirconia.