Aging studies of light cured dimethacrylate-based dental resins and a resin composite in water or ethanol/water

Objective. To study the aging of neat resins, prepared from bis-GMA, UDMA, D(3)MA or a mixture of bis-GMA/UDMA/D(3)MA (65/20/15w/w/w), in water or 75% (v/v) ethanol/water 37 degrees C. Also the study of aging of Heliomolar RO, which is a radiopaque, microfilled, light cured composite, the resin matrix of which is the copolymer of bis-GMA/UDMA/D3MA (65/20/15 w/w/w). Methods. Samples of neat resins and Heliomolar RO prepared by light curing were immersed in water or 75% (v/v) ethanol/water 37 degrees C, for 1, 7 or 30 days. Then the flexural and tensile strength were determined. The fractured surface of samples after the flexural tests was observed by scanning electron microscopy. Results. Bis-GMA and copolymer resin did not showed any significant change in mechanical properties after immersion in water or 75% (v/v) ethanol/water 37 degrees C, for 30 days. On the contrary UDMA, D3MA and the composite Heliomolar RO showed a significant decrease. Significance. The results obtained showed that the effect of aging in water or ethanol/water solution on mechanical properties of a light cured dimethacrylate resin depends on the chemical structure of resin. In the case of resin composite this effect depends on the filler-matrix bond strength. (C) 2006 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.