The Effect Of Dentin Pretreatment On Microtensile Bond Strength Of Resin Cements

Background:With advances in adhesive dentistry, resin cements have played an important role in prosthodontics. Resin cements present several advantages when compared to conventional luting agents, such as improved retention, minimal solubility in the oral environment, less microleakage,and acceptable biocompatibility. Resin cements are developed from etch-and-rinse, self-etch to self-adhesive based upon the nature of the treatment to the tooth substrate. There is a question whether the formation of dentin-adhesive interaction zone is sufficient to create a stable adhesion, since the residual smear layer might disturb monomer infiltration into underlying dentin. Several in vitro studies demonstrated that predominant failures of bonding occurred at the cement-dentin interface.To the author's knowledge, few studies have focused on the efficacy of smear layer and debris removal with pretreatment of resin cements.Objective:The aim of this study is to evaluate the effect of pretreatment on tensile bond strength (TBS) of resin cements. Methods:1.48 dentin surfaces of human were treated by one of the follows:(1) distilled water; (2) 35% phosphoric acid; (3) EDTA; (4) MTAD. Then composite blocks were luted to human dentine using resin cement (Super Bond C&B, Panavia F 2.0, Relyx Unicem). After storage in deionized water for 24 h, each specimens was sectioned into 1 mm2 beams. Then TBSs were measured and the fractured surfaces were examined by field-emission scanning electron microscopy (FE-SEM). Finally two-way ANOVA and Fisher's PLSD tests were performed.2.12 dentin surfaces of human were treated by one of the follows:(1) distilled water; (2) 35%phosphoric acid; (3) EDTA; (4) MTAD. The surfaces were examined by field-emission scanning electron microscopy.Results:1. Microtensile bond strength The highest mean microtensile bond strength was found for Panavia F2.0 with MTAD (25.95±1.66 MPa). The lowest was found for Super Bond C&B with PA pretreatment(7.18±1.03 MPa).The microtensile bond strength of MTAD groups were significant higher than those of the control, PA and EDTA groups acid in Panavia F 2.0, Relyx Unicem groups(P<0.05). All kinds of dentin pretreatments groups showed significant higher microtensile bond strength than control groups in Panavia F2.0 and Relyx Unicem (P<0.05) except PA in Panavia F2.0 (P>0.05). All kinds of dentin pretreatments groups showed significant lower microtensile bond strength than control groups in Super Bond C&B (P<0.05).2. Microscopic observations For PA and EDTA treated dentin, the smear layer was completely removed and a microporous, demineralized collagen matrix could be observed in the intertubular dentin.For MTAD treated dentin, the smear layer was completely removed. 3. The prevalent type of failure was adhesive failure along the cement—dentin interface and some mixed failures with a combination of adhesive failure along the cement-dentin/composite interface and cohesive failure within the cement or dentin.Conclusions:Pretreatment will affected the integrity of dentine bonding with Panavia F 2.0 and Relyx Unicem. But for Super Bond C&B pretreatment will reduce bond strength.