Schwickerath adhesion tests of porcelain veneer and stereolithographic additive-manufactured zirconia

The adhesion between zirconia core and porcelain is an essential factor that affects the long-term stability of zirconia-based restorations. This paper was aimed to evaluate the adhesion between commercially available porcelain veneering materials and digital light processing (DLP)-manufactured zirconia. The adhesion characteristics were compared with those of veneer and zirconia core fabricated by conventional subtractive manufacturing. The DLP-manufactured zirconia substrates were veneered by one experienced dental technician with the following porcelains: IPS e.max Ceram (DE), VM9 (DV), and VintageZR (DZ). The subtractive-manufactured substrate was veneered by VintageZR (SZ) only. The results showed that the zirconia fabricated by DLP showed adequate bonding when veneered by commercial dental porcelains. Among the DLP-manufactured zirconia substrates with different brands of dental porcelains, DZ showed a significantly higher bond strength and strain energy release rate than the other two groups (p < 0.05). No significant statistical difference in bond strength or strain energy release rate was observed between substrates veneered by the same porcelain (p > 0.05). On the basis of the results, the adhesion between DLP-manufactured zirconia and the veneer ceramic can be affected by the brand of the dental porcelain. The zirconia fabricating method did not affect bonding of the zirconia/porcelain structure.