Enamel and dentin bond strength of new simplified adhesive materials with and without preliminary phosphoric acid-etching.

Purpose: To assess the influence of preliminary phosphoric acid-etching on shear bond strength (SBS) to enamel and dentin of a self-adhering restorative composite and of a new self-etch adhesive used in combination with the proprietary flowable composite.

Methods: 100 human molars were selected. SBS was assessed on flat buccal enamel surfaces and mid-coronal dentin. Teeth from each group were divided into five subgroups (n=10): (1) FL: etch-and-rinse adhesive OptiBond FL/Premise flowable; (2) XTR: 2-step self-etch adhesive OptiBond XTR/Premise flowable; (3) eXTR: OptiBond XTR on etched substrates/Premise flowable; (4) VF: self-adhering flowable composite Vertise Flow; (5) eVF: Vertise Flow on etched substrates. Specimens were stressed in shear until failure. Failure modes were evaluated under a stereomicroscope. Data were analyzed by two-way ANOVA and Fisher's exact test (P< 0.05).

Results: Dental substrate, material and between-factor interaction significantly influenced SBS (MPa). In FL group (16.83 +/- 2.93) significantly higher SBS to enamel than in the other groups (XTR 8.59 +/- 4.39; eXTR 7.04 +/- 3.63; VF 6.61 +/- 2,41; eVF 9.87 +/- 4.24) was measured. On dentin FL (8.15 +/- 3.88) performed similarly to XTR (10.60 +/- 5.0), eXTR (9.60 +/- 4.91) and eVF (5.48 +/- 4.94); VF recorded significantly lower SBS (2.94 +/- 2.79 MPa). Failure modes differed significantly among groups.