Pinos de fibra de vidro customizados manualmente e pela técnica cad/cam : estudo da interface de união

Abstract

Objectives: To evaluate the pull-out bond strength of a prefabricated fiberglass post (PP), relined fiberglass post (RP) or milled fiberglass post (MP) luted with Multilink N (MN), RelyX Unicem 2 (RXU2) or RelyX Ultimate (RU) to weakened root dentin. The thickness of the resin cements and the presence of voids in the resin cement line were also analyzed. Additionally, a case report described a clinical protocol to manufacture customized monolithic fiberglass post and core using CAD/CAM technology. Methods: The coronal portions of 90 bovine incisors were removed, and the root canals were weakened and endodontically treated. The teeth were randomly divided into nine groups (n=10) according to the post type (PP, RP or MP) and resin cement (MN, RXU2 or RU) used to lute the posts. The specimens were scanned using micro-CT to analyze the thickness of the resin cement and the presence of voids. The specimens were submitted to mechanical cyclic loading (500,000 cycles at 50 N load), and the pull-out bond strength test was performed in a universal testing machine at a crosshead speed of 1 mm/min. Two-way ANOVA followed by Tukey’s test was used to analyze the pull-out bond strength and resin cement thickness data. The void scores were analyzed by the Kruskal-Wallis test followed by Bonferroni test. In the clinical case, a 44-year-old female patient received a monolithic fiberglass post and core on tooth 21 from scanning the model and milling a fiberglass block. Results: The interaction between factors (post x resin cement) was significant (p=0.0001) for the pull-out bond strength. Higher pull-out bond strengths were obtained for RP and MP compared to PP. The post factor was significant (p=0.0001) for resin cement thickness, which was higher for PP (1054 μm), followed by MP (301 μm) and RP (194 μm). More void formation was observed for PP, and less void formation was observed for RP, differing significantly among the posts. Conclusion: Post customization (RP and MP) decreased resin cement thickness and void formation, favoring a higher pull-out bond strength. Resin cements requiring an adhesive application (MN and RU) favored a higher pull-out bond strength than self-adhesive resin cement (RXU2). The manufacture of fiberglass post and core is a reliable and reproducible technique in flared root canals.