Effect of Endodontic Retreatment Protocols on Bond Strength of Fiberglass Post to Root Canal Dentine: An In-vitro Study

Introduction: Fiberglass Posts (FGPs) associated with composite resin foundation materials have become the primary alternative to restoring teeth with root canal treatment presenting excessive coronal destruction. Despite technical evolution, loss of retention between FGP and root dentine continues to be reported. Aim: To examine the effect of endodontic retreatment protocols on the bond strength of FGP to radicular dentine. Materials and Methods: This in-vitro study was conducted at Evangelical University of Goias, Brazil from August 2019 to June 2020. Thirty freshly extracted bovine incisors were instrumented, filled and distributed into three experimental groups with 10 incisors in each groups. Group 1 was control, Group 2 had incisors with gutta-percha removed using K-type files and Group 3 had incisors with gutta-percha removed using ProTaper Universal Retreatment instruments. After root canal retreatment and re-sealing, the fiber posts were cemented into prepared post spaces using a resin-based cement. Roots were transversally sectioned into six 1 mm thick specimens. The push-out test was performed, and the modes of failure were evaluated. Data were analyzed with two-way Analysis of Variance (ANOVA) and Tukey's test. Results: There was no significant difference between the mean bond strength values in group 1,2 and 3 with p-value>0.05. The cervical third of root canal presented higher bond strength values compared with the middle and apical thirds. However, significant differences were observed only for the control group (p-value=0.005). Adhesive failure between resin cement and radicular dentine was the most prevalent type of failure. Conclusion: The endodontic retreatment protocol did not influence the bond strength of FGP to radicular dentine.