Effect of the Etching Duration and Ultrasonic Cleaning on Microtensile Bond Strength Between Feldspathic Ceramic and Resin Cement

This study assessed the effect of different etching time of hydrofluoric acid and ultrasonic cleaning of the etched ceramic surface on the resin microtensile bond strength stability to a feldspathic ceramic. The research hypotheses investigated were: (1) different etching time does not affect the adhesion resistance; (2) ultrasonic cleaning improves the adhesion resistance. Forty-eight (48) blocks ceramic (6x6x5mm) were obtained. The cementations surfaces were duplicated in resin composite. The six study groups (n=8) were: G1: etching with 10% HF (30s) + Silane; G2: 10% HF (1min) + Silane; G3: 10% HF (2min) + Silane; G4: 10% HF (30s) + ultrasonic cleaning (4min) in distilled water + Silane; G5: 10% HF (1min) + ultrasonic cleaning + Silane; G6: 10% HF (2min) ultrasonic cleaning + Silane. The cemented blocks were sectioned and microbars for the microtensile test. The etching period did not create significant difference among the groups (P= 0.156). Significant influence of ultrasonic cleaning was observed (P= 0.001) (Two-way ANOVA and Tukey's test, p>0.05). All the groups with ultrasonic cleaning had higher bond strength (range: 19.38 – 20.08 MPa) when compared to the correspondent group (range: 16.21 – 17.75 MPa). Conclusions: The bond strength between feldspathic ceramic and resin cement is not affected by different etching times with HF; b) Ultrasonic cleaning increases the bond strength between ceramic surface and resin cement, regardless of the etching time.