Bonding to eliminate interfacial gaps in fiber post-retained restorations

Bonding to eliminate interfacial gaps in fiber post-retained restorations Background.—Fiber-reinforced, epoxy resin- based posts can be used with methacrylate-based dentin adhesives and resin cements as alternatives to cast or prefabricated metal posts to restore endodontically treated teeth. In theory, the hybridization of intraradicular dentin achieved by applying dentin adhesives should eliminate interfacial gaps, which would improve the coronal sealing and retention of teeth restored with fiber posts. Studies of microtensile bond strength have not found the good results that were expected. It is possible that the retention of bonded fiber posts results more from friction than bonding. Methods.—Two types of fiber posts were used with the corresponding etch-and-rinse adhesives and dualcured resin cements to bond post spaces in 40 extracted single-rooted incisors. Groups 1 and 2 had the fiber post Tech 2000 plus Single Bond adhesive and RelyX ARC resin cement. In group 1, no light curing was done before resin cement insertion; in group 2, the adhesive was light cured for 20 seconds. Groups 3 and 4 had Endopost placed with All-Bond 2 adhesive and Duo-Link resin cement. A mixture of D/E Resin and Pre-Bond was used to make the resin dual-curable in group 3. Only D/E Resin was used and light cured for 20 seconds before applying resin cement in group 4. The interfaces were sectioned longitudinally to determine the extent of dentin hybridization in the coronal and middle thirds of the root canals. Resin replicas were evaluated to see whether interfacial gaps occurred.

the hybrid layer surface or the post-cement interface. Where there were no gaps in the cement-dentin interface, delamination of the fiber post from the resin cement was often noted. Discussion.—Hybridization of the interradicular dentin did not improve the integrity of the coronal seal or the resistance to dislocation of fiber post-retained restorations. The occurrence of interfacial gaps demonstrated how hard it is to achieve a sufficient bond to post spaces with low compliance and high C-factors. Thus, the clinical usefulness achieved with fiber posts most likely results from frictional forces.

Clinical Significance.—While the idea of bonding a post in a root canal sounds like a good idea, this study revealed significant interfacial gaps between dentin and post. Retention is apparently due more to mechanical friction than bonding.

Pirani C, Chersoni S, Foschi F, et al: Does hybridization of interradicular dentin really improve fiber post retention in endodontically treated teeth? J Endodont 31:891-894, 2005 Reprints available from FR Tay, Prince Philip Dental Hosp,The Univ of Hong Kong, Pokfulam, 34 Hospital Rd, Hong Kong SAR, China; e-mail: [email protected]

Results.—Gaps formed in all sections of the teeth regardless of the bonding system used. The gaps were along

Volume 51 • Issue 4 • 2006 249