Fiber Post Bonding Effectiveness to Root Canal and Composite Core

Objectives: This study evaluated the effects of fiber post, silanization and luting system on interfacial strength to root canal dentin and composite core. Methods: Root canals of 120 crownless human teeth were instrumented. Post space was prepared to receive one of the following cylindroconical fiber posts: DT Light Post (L), DT White Post (W) and FRC Postec (P). Each post group was bonded using four luting systems: Excite DSC/Variolink II (EV), ED Primer II/Panavia F2.0 (EP), RelyX Unicem (RU) and Prime & Bond NT including Self Cure Activator/Dyract Cem plus (PD). In each of the 12 subgroups (n=10), half of the posts were silanized (Monobond-S). Composite cores (MultiCore HB) were build up to the coronal end of all posts. After water storage (37 degrees C, 24 h), 2 mm thick slices were cut from each sample, one from the restored root and one from the composite core. Interfacial push-out bond strengths of the posts were determined in a universal testing machine (Zwicki 1120). Failure modes were analyzed in the SEM. Results: Type of post and type of luting system had significant effects on both, post-to-dentin (p<0.0001) and post-to-core strengths (p=0.004). Silanization did not significantly influence post-to-dentin strengths (p=0.497), but enhanced post-to-core strengths (p=0.039). Mean post-to-dentin strengths were highest with EV/P (31±5 MPa) and lowest with PD/W (14±9 MPa). Higher post-to-core strengths were found for bonding P. With EV and PD, debonding of the posts from the root canals occurred predominantly between post and luting cement, while EP and RU showed mixed failures. In the composite cores, no failures were observed between cores and luting cements. Conclusion: Retention of fiber posts in root canals is influenced by the selected type of post and type of luting system, whereas silane treatment of the fiber posts seems to be less relevant.