Bond Strength Evaluation between Different Glass Fiber Post Systems to Restore Weakened Roots

A new bundled glass fiber-reinforced resin post was developed to be used in post-endodontic restoration. We evaluated the bond strength of a single prefabricated glass fiber post (GFP) and a bundled glass fiber-reinforced resin post (GT), used alone or combined, to restore weakened roots. Fifty bovine incisors roots were weakened with a diamond bur, except for those from the control group. The root canals were endodontically treated (Pro Taper Next system, gutta-percha, and endodontic cement), and the roots were divided into five groups (n = 10): Reb-single prefabricated GFP (Rebilda Post-Voco); GT-bundled glass fiber-reinforced resin post (Rebilda Post GT-Voco); RebGT-association between the prefabricated GFP (Reb) and the bundled one (GT); CP-prefabricated GFP customized with composite resin; and Cont-singular post in a non-weakened root (Control). All posts were cemented using a universal adhesive system (Futurabond U) and dual-cure resin cement (Rebilda DC-Voco). Afterwards, two slices were obtained from each root third (cervical, middle, and apical) and submitted to a push-out bond strength test. Data were analyzed regarding the post system used and the root thirds by two-way ANOVA, followed by Tukey's test (p < 0.05). There were higher bond strength means for the RebGT and CP groups, presenting values similar to the control. The Reb and GT groups showed lower values. The adhesion to deeper thirds of the root canal remains a challenge for adhesive dentistry and is not related to the design of the post. Additionally, the rehabilitation of teeth with weakened roots requires the customization of the glass fiber post with composite resin or the association between prefabricated options with multiple posts.