Effect of the combined zirconium dioxide surface treatment on the shear bond strength of a veneering ceramic to zirconium dioxide

BACKGROUND: Yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) is used as a core material in all-ceramic restorations. The delamination and chipping of a veneering ceramic are the most common complications in the case of zirconia-based restorations. OBJECTIVES: The aim of the study was to investigate the effect of the combined treatment of the zirconium dioxide (ZrO2) surface (airborne-particle abrasion with liner application) on the shear bond strength (SBS) of a veneering ceramic. MATERIAL AND METHODS: Thirty pre-sintered ZrO2 cuboidal specimens (VITA YZ® HT) were sub-divided into 3 groups: group C consisted of 10 specimens without treatment at the sintering stage; group SZ1 consisted of 10 specimens treated with airborne-particle abrasion (50-micrometer paricles of aluminum oxide - Al2O3; Korox® 50), and then coated with a 0.1-millimeter liner (IPS e.max® Ceram ZirLiner) after sintering; group SZ2 consisted of 10 specimens treated with airborne-particle abrasion (50-micrometer particles of Al2O3), and then coated with a 0.2-millimeter liner after sintering. Ceramic veneers (IPS e.max Ceram Dentin) were then applied using the layering technique. After that, the SBS tests were conducted. RESULTS: The results showed that the combined treatment of the ZrO2 surface significantly affected SBS (p < 0.01). The highest mean value was shown in group C (12.441 ±2.284 MPa), followed by group SZ2 (7.889 ±0.794 MPa), whereas the lowest mean value was observed in group SZ1 (5.580 ±0.843 MPa). CONCLUSIONS: The combined treatment of the pre-sintered ZrO2 surface significantly reduced the SBS of a veneering ceramic. However, the combined surface treatment with a liner thickness of 0.2 mm significantly enhanced the SBS of a veneering ceramic compared to the same combined treatment but with a liner thickness of 0.1 mm.