Effect of surface treatment and cleaning on the bond strength to polymer-infiltrated ceramic network CAD-CAM material

Statement of problem: Optimal composite resin bonds to polymer-infiltrated ceramic network (PICN) computer-aided design and computer-aided manufacturing (CAD-CAM) materials are essential for clinical success. However, comparative bond strength studies on the influence of different etching and cleaning methods on these materials are lacking. Purpose: The purpose of this in vitro study was to measure and compare the microshear bond strength (μSBS) of a composite resin cement with that of a PICN material after different surface treatment and cleaning methods. Material and methods: Seventy specimens of a CAD-CAM PICN were divided into 7 groups (n=10): no treatment (control), hydrofluoric acid etching for 20 seconds (HF20), 60 seconds (HF60), 120 seconds (HF120), HF20 + phosphoric acid for 60 seconds and ultrasonic bath for 5 minutes, HF60 + PH, and HF120 + PH. After surface treatment, a silane coupling agent and composite resin cement were applied. Microshear bond strength was determined, and data were analyzed with 1-way ANOVA and Tukey post hoc multiple comparison tests (α=.05). Results: All HF acid treatments resulted in a significant increase in bond strength to the polymer-infiltrated ceramic network material (P=.02). Bond strength values for HF etching for 20 seconds were significantly lower than those for 60 seconds and 120 seconds (P=.034). No difference was found between 60 seconds and 120 seconds of HF etching time (P=.986). Additional surface treatment with phosphoric acid 60 seconds and ultrasonic bath 5 minutes did not improve the bond strength beyond values obtained by hydrofluoric acid treatment only (P=.834). Most failures were cohesive. Conclusions: Acid etching and surface treatment have significant effects on composite resin bond strength to a PICN CAD-CAM material. HF etching for 60 seconds or 120 seconds provides the highest bond strengths. Cleaning methods after etching did not have any significant effect on bond strength.