Push-Out Bond Strength and Sealing Effectiveness of Fiber-Post Bonding

Objectives: To evaluate the push-out bond strength and the sealing ability of five adhesive cements routinely used for fiber-post bonding. Methods: Fifty extracted single-rooted human teeth were sectioned at the CEJ and restored with translucent glass Parapost FiberLux posts (Coltène-Whaledent, USA) randomly luted with Panavia21/ED Primer (PAN, Kuraray), Clearfil Esthetic Cement/ED Primer II (CLF, Kuraray), Variolink II/Excite DSC (VAR, Ivoclar-Vivadent), RelyX Unicem (UNI, 3M-ESPE) or GC experimental self-adhesive cement (EGC). Posts were inserted at 10 mm from the CEJ. After one week water storage at 37°C, three sections (coronal, middle, apical) of 2 mm thickness were prepared. The sealing effectiveness was quantified with a fluid-filtration system (Flodec, De Marco Engineering, Switzerland) during 10 minutes. Afterwards, each sample was immediately subjected to the push-out test using a universal loading device (5848-MicroTester, Instron, USA). Data were analyzed with ANOVA (push-out) and Kruskal-Wallis (sealing effectiveness). Results: Push-out bond strength and sealing effectiveness were found not to be significantly different for the coronal, middle and apical sections, for each luting agent (p>0.01). The highest bond strength was observed for CLF (14.60±3.63 MPa), which was not significantly different from PAN (12.57±2.45 MPa, p=0.28) but significantly higher than VAR (11.09±4.09 MPa, p=0.005), UNI (11.29±4.31 MPa, p=0.01) and EGC (7.65±4.79 MPa, p<0.001). EGC scored significantly lower than the other cements (p<0.01). When evaluating the sealing effectiveness, no significant differences were observed among PAN (1.15x10^-2µl/min), CLF (2,37x10^-2µl/min), VAR (1,84x10^-2µl/min) and between UNI (7,76x10^-2µl/min) and EGC (40,82x10^-2µl/min). The latter luting agents scored significantly worse than the former ones. The push-out bond strength appeared directly correlated to the sealing effectiveness (p<0.001). Conclusions: Overall, the self-etching MDP-based (PAN, CLF) cements presented the best results. Although the bonding effectiveness of self-adhesive cements (UNI, EGC) appears promising, their interaction with root dentin may be too weak to minimize microleakage at the post-cement-dentin interface.