Dentin regional bond strength of self-etch and total-etch adhesive systems

Objectives: To evaluate the microtensile bond strength (MTBS) of self-etch (with or without H₃PO₄-etching) and total-etch bonding systems bonded to different regions of dentin. Methods: Long flat dentin cavity preparations extending from top-crown to root-apex within the same tooth were performed and bonded: using two-step (Clearfil SE Bond/SEB, Resulcin Aqua Prime/RES) and one-step (Etch & Prime 3.0/EP, One-Up Bond F/OUB, Prompt L-Pop/PLP, Solist/SOL and Futurabond/FUT) self-etch adhesives; these same adhesives were also applied following H₃PO₄-etching of dentin and finally two more groups were bonded with total-etch adhesives (Single Bond/SB and Prime & Bond NT/PBNT). Build-ups of resin composite were constructed incrementally to ensure sufficient bulk for the MTBS test and the different regions of dentin were identified by painting with different colours on the top of the resin composite. Specimens were sliced into beams and tested in tension. ANOVA and multiple comparisons tests were used (p < 0.05). Results: Regardless of the tested dentin region, SEB attained the highest MTBS to smear layer-covered surfaces (i.e., coronal dentin: 42.7 MPa), while H₃PO₄-etching of dentin hampered bonds (i.e., coronal dentin: 27.7 MPa). When bonding with PBNT, SB, RES, EP, PLP, SOL and FUT, MTBS was similar for different dentin regions. H₃PO₄-etching of dentin did not alter the attained MTBS. Significance: SEB yielded the highest MTBS to all regions of dentin. When bonding to parallel-cut dentin, previous H₃PO₄-etching of dentin did not increase MTBS and differences in bond strength among dentin regions were absent.