Resistência à fratura de raízes enfraquecidas restauradas com pinos intra-radiculares e submetidas à ciclagem mecânica

• Ano de defesa: 2010
• Autor(a) principal: Nascimento, Maria Fernanda
• Orientador(a): Shinkai, Rosemary Sadami Arai
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Pontifícia Universidade Católica do Rio Grande do Sul; Porto Alegre
• Palavras-chave em Português: ODONTOLOGIA; ENDODONTIA; PRÓTESE DENTÁRIA; MATERIAIS DENTÁRIOS; RESISTÊNCIA DOS MATERIAIS (ODONTOLOGIA)
• Link de acesso: http://hdl.handle.net/10923/393

This in vitro study evaluated the fracture strength of endodontically treated, weakened root canals, which were restored with either cast metallic or glass fiber-reinforced resin posts (Exacto, Angelus Indústria de Produtos Odontológicos S/A, Londrina, PR, Brazil) and submitted or not to mechanical fatigue. Twenty extracted human teeth with standardized dimensions and no visible structural defects were used. The crowns were cut below the enamel-cement junction to result in 14-16 mm-length roots. The endodontic treatment was performed by using the stepwise technique; the canals were prepared for post insertion with a bur of the glass fiber-reinforced resin post system (# 1. 6 mm-diameter). The roots were weakened by removing intracanal dentin with a tapered diamond bur (4 mm-length) and randomly divided into four groups (n=5/group) according to the type of post (metallic or glass fiber-reinforced resin post) and type of treatment (with or without mechanic cycling). For the metallic posts, the intracanal portion was modeled and cast in Ni-Cr alloy. The resin posts had the crown portion built with nanoparticle composite Z250 (ESPE, 3M) using prefabricated polyesther crowns of standardized shape according to the cast posts. All posts and metallic crowns were cemented with RelyX Unicem. The roots were covered with impression material to simulate the periodontal ligament and embedded in acrylic resin. Two groups were submitted to mechanic cycling with 300,000 cycles, 50 N of load corresponding to a pressure of 1. 13 bars, and frequency of 1 Hz. Specimens were loaded at 45 degrees in a universal testing machine at a crosshead speed of 0. 5 mm/min until failure. The mode of failure was classified as repairable or nonrepairable. The results showed that the metallic posts with no mechanic fatigue had the highest fracture strength (484 N); the resin posts with mechanic cycling showed the lowest values (259. 9 N). The teeth with cast posts had higher strength than the ones with resin posts, but they also showed more nonrepairable failure. Mechanical cycling reduced the fracture strength but did not affect the failure mode.