Efeito do material de pistão no comportamento de fratura de cerâmicas vítreas

Abstract

The objective of this study was to evaluate the influence of the piston material, used in a mechanical test, in the failure behavior of dental ceramics. Also to investigate the fracture load and failure mode of two types of ceramics, a porcelain and a lithium disilicate glass-ceramic. Forty specimens of each ceramic were produced by cutting CAD-CAM blocks in 1.5 mm slices, and were cemented with resin cement over fiber-reinforced epoxy resin substrates (G10). Specimens were sub-divided into two groups, according the piston type (n=20): metal (stainless steel) or composite (G10). Tests were performed with a compressive monotonic load, using a universal testing machine, at 0.5 mm/min cross-head speed, in a 37º C water bath. The acoustic emission related to the initial flaw was detected with a device and the fracture load was registered. Failure analysis was performed with transillumination. Data were analyzed with Kruskal-Wallys and Tukey´s test (α=0.05). The piston material had no influence on the fracture load of lithium disilicate glass-ceramic. Yet, porcelain tested with composite piston showed significatively higher fracture load in comparison to metal piston. When tested with metal piston, lithium disilicate glass-ceramic had higher fracture load than porcelain. Lithium disilicate glass-ceramic specimens showed radial cracks. For porcelain, cone cracks combined with radial cracks were also found. It was concluded that the effect of the piston material on the fracture load and failure behavior depends on the ceramic material evaluated. Porcelain was more susceptible to contact damages.