The aim of the study was to evaluate the fracture behavior of Eclipse Resin System, used in complete dentures technology. 30 samples were evaluated with Zwick Roel device. All samples had defects: The analysis of fracture behavior was performed with an Olympus type SZX7 stereo-microscope. On transverse section, samples breaking had an initiation zone: 15% in center and 85% at the edge. The zone of final fracture was sharp, with granular aspect. The fractured samples showed brittle characteristics without massive elongation of plastic deformation before fracture. Defects from material\'s structure had a negative impact on mechanical resistance of prostheses. Keywords: fracture, dental resins