Dynamic thermomechanical properties and sorption characteristics of two commercial light cured dental resin composites

Objectives. The first objective of this work is the study by DMTA of viscoelastic properties (E', E '', tan delta, T-g) of two current dental resin composites Tetric EvoCeram (nanohybrid) and Heliomolar (microfilled) in dry condition and in water for up to 30 days. The second objective is to determine the sorption characteristics of these composites in water and ethanol/water solution 75 vol.%. Methods. For DMTA the bar-shaped specimens divided into five groups of three samples each. The first group consisted of dry samples measured 1 h after curing. The second and third group consisted of samples, which had been heated in air at 80 +/- 1 degrees C for 1 day or had been stored in distilled water at 80 +/- 1 degrees C for 1 day. The fourth and fifth group consisted of samples, which had been stored in distilled water at 37 +/- 1 degrees C for periods 1 and 7 days correspondingly. Also specimen discs (15 mm in diameter and 1 mm in thickness) were immersed in water or a 75 vol.% ethanol/water solution at 37 +/- 1 degrees C. At fixed time intervals they were removed, blotted dry to remove excess liquid, weighted and returned to the liquid. This process continued for 30 days. Results. The viscoelastic properties (E', E '', tan delta, T-g) of the two composites treated under different conditions were recorded and compared. Also the mass uptake, diffusion coefficient, solubility and volumetric changes for immersion of composites in water and ethanol/water solution 75 vol.% at 37 +/- 1 degrees C were determined. Significance. Tetric EvoCeram a nanohybrid composite with similar about resin matrix with Heliomolar which is a microfilled showed better dynamic thermomechanical properties and sorption characteristics than Heliomolar. (C) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.