Métodos para simular a usinagem em CAD/CAM em uma cerâmica de dissilicato de lítio: efeito na topografia, comportamento à fadiga e adesão

• Ano de defesa: 2021
• Autor(a) principal: Pilecco, Rafaela Oliveira
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria; Brasil; Odontologia; UFSM; Programa de Pós-Graduação em Ciências Odontológicas; Centro de Ciências da Saúde
• Palavras-chave em Português: Desenho assistido por computador; Fadiga; Manejo de espécimes; Resistência ao cisalhamento; Computer-aided design; Fatigue; Shear strength; Specimen handling; CNPQ::CIENCIAS DA SAUDE::ODONTOLOGIA
• Link de acesso: http://repositorio.ufsm.br/handle/1/23223

The present dissertation is composed of two studies that evaluated the topographic characteristics, bond strength and fatigue behavior of lithium disilicate specimens fabricated by different laboratory methods aiming to simulate milling through Computer aided-design/Computer aided manufacturing (CAD/CAM). The first study investigated the bond strength of a lithium disilicate ceramic (IPS e.max CAD, Ivoclar Vivadent) with a resin cement when specimens were produced by six different fabrication methods [mirror-polished (POL); #60 silicon carbide paper (SiC group); #60 wood sandpaper (WS group); fine diamond bur (group DB); a CAD/CAM bur adapted to a mandrel and a handpiece (MANDREL group)] or through CAD/CAM milling (CEREC inlab MC XL, Sirona) (control group - CAD/CAM). Lithium disilicate specimens were etched with 5% hydrofluoric acid for 20 seconds and subsequently silanized. Resin cement cylinders were bonded, submitted to the microshear test and evaluated microscopically for the failure pattern. Roughness, contact angle analysis, fractal dimension and scanning electron microscopy were performed. The fractal dimension showed different complexities according to the protocols. None of the experimental simulation protocols presented surface roughness values similar to the CAD/CAM group, however, they resulted in similarities in the surface topography. No differences were found between the simulated groups and the CAD/CAM regarding the results of bond strength test, but the polished group resulted in lower microshear bond strength. Most of the failures were predominantly adhesive. Thus, in-lab simulation methods proved to be viable alternatives in the fabrication of specimens with adhesive behavior similar to milled ones. The second study evaluated the same in-lab simulation methods on fatigue behavior. Disilicate discs (n= 19, Ø= 13.5 mm, 1.5 mm thick) were made according to the same protocols previously described. The specimens were cemented adhesive to epoxy resin discs (material analogue to dentin; Ø= 12 mm, 2.0 mm thick) and tested in fatigue according to the step-stress methodology (initial load of 200 N; 20 Hz of frequency, 50 N load increments, 10,000 cycles per step). Complementary analyzes of contact angle, roughness and fractal dimension were performed. The fatigue performance was affected by the fabrication methods (CAD / CAM 1250 <SiC 1355 = WS 1357 < DB 1476 = MANDREL 1526 < POL 1752). The roughness parameters of CAD/CAM group were similar with the SiC, WS and MANDREL groups. The contact angle pre-etching with hydrofluoric acid was similar between the CAD/CAM, SiC, WS and DB groups, however post etching it were similar between all groups, except for the polished one. Therefore, even though the methods presented some topographic similarities, no in-lab simulation method was able to mimic the fatigue behavior of specimens milled via CAD/CAM.