Effect of water storage on the impact strength of three glass fiber-reinforced composites

Objectives: The effect of water sorption on the impact strengths of two preimpregnated fiber-reinforced composites (FRCs) and one impregnated FRC were studied. All FRCs were available clinically. Methods: Eight 1.0 mm x 2.0 mm x 25.0 mm bar-shaped specimens of each material were prepared according to manufacturers' instructions. The impact strength of each specimen was tested (adoption from ISO 179-1 Plastics-Determination of Charpy impact properties) after the specimens were immersed in 23.0 +/- 1 degrees C distilled water for seven, 60 and 180 days. The data were analyzed using the Weibull method. Scanning electron micrographs were taken to examine the mode of failure. Results: Weibull analysis of the B10 strength of the FRCs showed that the difference in impact strength for each FRC due to the duration of water immersion was not significant (P > 0.05). The impact strength of preimpregnated E-glass FRC (Vectris) (75 kJ/m(2)) was not significantly different from the preimpregnated S-glass FRC (FiberKor) (66 kJ/m(2)) (P > 0.05). The impregnated FRC possessed impact strength (42 kJ/m(2)) that was not significantly different from the preimpregnated S-glass FRC but was significantly lower than the preimpregnated E-glass FRC. X 100 SEMs of the three types of FRC specimens revealed fiber failure to be the predominant mode of failure. Significance: Water immersion up to 180 days duration did not significantly affect the impact strength of three FRCs. The impact strength of the impregnated FRC was not significantly different from the preimpregnated S-glass FRC but was significantly lower than the preimpregnated E-glass FRC. (c) 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.