Effect of Surface Treatments on Porcelain Adherence to Non-Cast Titanium

Objectives: This study was to evaluate the porcelain adherence to non-cast titanium with different surface treatments. Methods: Non-cast titanium sheets (25 mm x 3 mm x 0.5 mm) were prepared using machining process which simulated the CAD/CAM procedures. The non-cast titanium sheets were sandblasted with 120 mm (group-120SB) or 250 mm (group-250SB) Al₂O₃ particles. Sequentially, the group-120SB specimens were subjected to four different surface treatments, including immersion in HNO₃/HF (group-acid), immersion in NaOH/CuSO₄ (group-alkaline), immersion in NaOH/CuSO4 followed by HNO₃/HF (group-alkaline/acid), and coating with gold-paste (group-gold). Then, the low-fusion porcelain was fired onto the central part (8 mm x 3 mm x 1 mm) of titanium sheets. According to ISO 9693 specification, the three-point bending tests were carried out for all test groups. The bond strength (MPa) of porcelain-titanium was analyzed uisng one-way analysis of variance (a=0.05) and Tukey's multiple comparison test when necessary. The fracture surfaces were examined using scanning electron microscopy/energy dispersive spectroscopy. Results: Surface treatment showed a significant influence on the bond strength of porcelain-titanium (P < 0.01). The group-acid showed the highest bond strength (32.9±1.7 MPa), followed by the group-250SB (30.3±4.1 MPa) and group-120SB (28.1±1.3 MPa). Increasing the Al₂O₃ particle size for sandblasting led to an increase in bond strength. The group-gold showed the lowest bond strength (< 20 MPa). However, no significant differences were found between group-alkaline and group-alkaline/acid. Conclusion: The bond strength between porcelain and non-cast titanium can be improved by acid immersion before porcelain firing, while gold-paste coating may reduce the bond strength of porcelain-titanium.