Repair Bond Strength of a Resin Composite to Plasma-Treated or UV-Irradiated CAD/CAM Ceramic Surface

The aim of this study was to investigate whether atmospheric-pressure plasma (APP) or ultraviolet (UV) irradiation could alter the hydrophilicity of a computer-aided design/computer-aided manufacturing (CAD/CAM) glass ceramic surface, and thereby enhance the repair bond strength between the ceramic and a resin composite. Forty-eight leucite-reinforced glass ceramic discs were treated with 40% phosphoric acid and randomly assigned into one of six groups: Group 1, control; Group 2, treated with a mixture of Clearfil SE Bond primer (SEP) and Clearfil Porcelain Bond Activator (PBA); Group 3, subjected to APP irradiation for 10 s; Group 4, subjected to UV irradiation for 60 min; Group 5, APP irradiation followed by SEP/PBA; and Group 6, UV irradiation followed by SEP/PBA. After treatment, discs were bonded with resin composite using Clearfil SE Bond and stored in water at 37 degrees C for 1 week. We then tested how these treatments affected the microtensile bond strength (mu TBS) and measured changes in the water contact angle (CA). Samples from Group 2 showed the highest mu TBS (44.3 +/- 6.0 MPa) and CA (33.8 +/- 2.3 degrees), with no significant differences measured between Groups 1,3, and 4 (p < 0.05). Furthermore, the additional treatments of APP or UV before SEP/PBA had no effect (Group 5, p = 0.229) or a reduced effect (Group 6, p = 0.006), respectively, on mu TBS. Overall, APP or UV irradiation before SEP/PBA treatment did not enhance the repair bond strength.