Method:Five self-etch adhesives, OptiBond XTR (OX, Kerr), Scotchbond Universal (SU, 3M ESPE), G-aenial Bond (GB, GC), Prime & Bond Elect (EL, Dentsply), and All Bond Universal (AU, Bisco), were selected. Initial shear bond strengths (SBS) of Z100 Restorative (3M ESPE) to human enamel and dentin were determined, with and without phosphoric acid pre-etching (35%, 15 sec), prior to application of the adhesive (15 specimens for each adhesive). A staircase method of fatigue testing (initial load at approximately 50% of SBS) was then used with an ElectroPuls E1000 machine to determine SFL to enamel and dentin using 10 Hz frequency for 50,000 cycles (30 specimens for each test). A metal ring with an internal diameter 2.4 mm was used to bond composite to flat ground (4,000 grit) tooth surfaces for determination of both SBS and SFL. A two-way ANOVA and Tukey’s post hoc test were used for analysis of SBS data and a modified t-test with Bonferoni correction was used for SFL data.
Result:The SFL of enamel bonds was significantly higher (p<0.05) for specimen groups with phosphoric acid pre-etching (19.6–25.1 MPa) compared to no pre-etching (10.0–17.8 MPa). The SFL of dentin bonds of SU, GB, and OX, with phosphoric acid pre-etching (11.5-22.2 MPa), tended to decrease the values compared to no phosphoric acid pre-etching (15.9–25.3 MPa). However, EL and AU with phosphoric acid pre-etching of dentin (13.6-13.7 MPa) demonstrated higher values than without phosphoric acid pre-etching (11.1-12.0 MPa).
Conclusion:The effect of using phosphoric acid pre-etching on SFL, prior to application of the self-etching adhesives, was dependent on the adhesive material and tooth substrate.