Bond Strengths of Resin Cements to Root Canal Dentin

Objectives: to evaluate the push-out bond strength of translucent fiber posts (WhitePost DC, FGM; FRC Postec Plus, Ivoclar Vivadent) to intraradicular dentin at three different levels (cervical, middle and apical) using a dual-cure (AllCem, FGM) or a self-curing (Multilink, Ivoclar Vivadent) resin cements. Methods: Thirty two freshly extracted, single-root teeth presenting 14mm-length root canals were selected. After endodontic therapy, the teeth were randomly divided in four groups: G1 = WhitePost DC (FGM) + AllCem (FGM); G2 = FRC Postec Plus (Ivoclar Vivadent) + AllCem (FGM); G3 = White Post DC (FGM) + Multilink (Ivoclar Vivadent); G4 = FRC Postec Plus (Ivoclar Vivadent) + Multilink (Ivoclar Vivadent). Previously to the insertion of the posts, the root canal walls were etched using 37% phosphoric acid (FGM) for 15s, and Excite DSC Single Dose adhesive system (Ivoclar Vivadent) was applied in all groups. After storage for 30 days at 37° C, each root was sectioned to obtain nine 1mm-thickness slices (three slices per third, i.e., C=coronal, M=middle, and A=apical). All slices were subjected to a push-out test (0.5mm/min cross-head speed) and subsequently analyzed under SEM for the type of fracture. The results were analyzed using two-way ANOVA and Scheffe's post hoc. Results: the mean bond strengths were (mean in MPa ± SD): G1C=12.2±6.7; G1M=7.5±4.8; G1A=6.2±4.1; G2C=12.3±4.9; G2M=8.4±5.0; G2A=6.7±5.2; G3C=14.3±5.5; G3M=10.4±6.1; G3A=7.9±4.7; G4C=9.3±6.5; G4M=7.8±6.4; G4A=5.7±4.2. There were no significant differences between groups. The apical third presented the lowest bond strengths. The SEM analysis of fracture patterns revealed differences between groups. Conclusions: The apical third has shown to be the most critical region for adhesive luting of posts.