Análise de resistência à fratura dos dentes tratados endodonticamente restaurados com pinos usinados comparados a outros retentores intrarradiculares

Abstract

The use of composite blocks/discs based on fiberglass and epoxy resin for milling for computerassisted technology - CAD/CAM enables the manufacture of machined intraradicular retainers, highly individualized to the root walls, in order to meet biological, functional and aesthetics, optimizing clinical time. However, there are no consolidated studies comparing this material to those already on the market, justifying the need for this research. This dissertation seeks to evaluate the fracture resistance and failure mode of the intraradicular post machined by the CAD/CAM system, comparing it to other intraradicular retainers, after mechanical cycling. For the study, 75 healthy bovine incisors were selected, where the coronary portion was sectioned in 16mm, thus standardizing the roots. All specimens were endodontically treated and filled with epoxy resin-based endodontic cement, were randomized and distributed into five groups (n=15) according to the type of intraradicular retainer: CMP - cast metal post; PF - fiberglass post; PA - anatomical post; PFA - fiberglass post associated with accessory posts and MP - machined posts CAD/CAM. Next, the space for the post was prepared at 12mm in depth, with a heated straight probe and the drill indicated for the post used in each group. Then, the channels were embrittled with a #4137 diamond tip, to simulate embrittled roots (with widened channels and thin walls). The retainers were cemented with self-adhesive resin cement, received metallic crowns and the periodontal ligament was simulated using polyether. The specimens were subjected to mechanical cycling in fatigue equipment (Instron Electropuls E3000, Instron, Norwood, MA - USA) with the following protocol: 15Hz frequency, 80N load, 37°C temperature and 100,000 cycles. The specimens that survived mechanical cycling were submitted to fracture resistance test in a universal testing machine (DL 2000, Emic, São José dos Pinhais, Brazil), at a speed of 0.5mm/min and a 45° inclination to the failure. After verifying the normality of the data, one-way analysis of variance (Oneway ANOVA) and Tukey's post hoc test (p=0.05) were performed. The group with cast metal core showed higher fracture resistance values than the other groups (p<0.05), which did not present significant differences between them (p>0.05). Thus, it was observed that machined CAD/CAM posts have fracture resistance values similar to conventional fiberglass post, anatomical post and to fiberglass post associated with accessory post, which are less resistant to fracture than cast metal post. As for failures, all groups had unfavorable failures, with fractures below the cemento-enamel line in most specimens.