Microtensile Bond Strength of Contemporary Adhesive Systems to Dentin

Objectives: The purpose of this study was to evaluate the microtensile bond strength (mTBS) and the interfacial ultrastructure of total-etch, self-etch and glass-ionomer based adhesives to dentin. Methods: The crowns of twenty-five extracted human third molars were sectioned vertically in mesio-distal direction by leaving the pulp chamber between the sections. To create buccal and lingual flat dentinal surfaces the sections were ground until pulp chambers were disappeared. Dentin surfaces were bonded with Single Bond (SB; 3M ESPE), One Step Plus (OSP; Bisco), Tyrian SPE+One Step Plus (TY; Bisco), Clearfil SE Bond (SE; Kuraray); Clearfil SE Bond Plus (SEP; Kuraray); Prompt-L Pop (PLP; 3M ESPE) and Reactmer Bond (RB; Shofu). Composite buildups were performed with Clearfil AP-X (Kuraray). Following storage in distilled water at 37⁰C for 24 hours, the bonded specimens were vertically sectioned into serial slabs, and further into beams with cross-sectional areas of 0.5mm². Each beam tested for microtensile bond strength using a Bencor Multi-T testing apparatus attached to an Instron Machine at a crosshead speed of 1mm/min. Data were analyzed using one-way ANOVA and Tukey’s post hoc test. Means with the same superscript letter are not statistically different at p< 0.05. Results: mTBS (mean±sd, MPa)(n=21): SB (70.74±12.75^a,c), OSP (78.17±7.43 ^c), TY(31.58±2.94^b), SE (69.63±10.29^a), SEP(62.69±9.18^a), PLP (29.13±10.16^b), RB(33.73±6.61^b). SEM observations showed that TY and PLP formed hybrid layers with a thickness approaching total-etch systems SB and OSP. SE created a thin hybrid layer, with SEP and RB hybrid layers were not clearly observed. Conclusion: The self-etch adhesives TY and PLP and glass ionomer-based adhesive RB exhibited significantly lower microtensile bond strength values than the self-etch adhesives SE and SEP and the total-etch adhesives SB and OSP. All adhesive systems achieved the formation of sealed interfaces however hybrid layer thickness depends on the material properties.