Simultaneous determination of polymerization shrinkage, exotherm and thermal expansion coefficient for dental resin-composites.

OBJECTIVES

To measure shrinkage strain, exotherm, and coefficient of thermal expansion (CTE), simultaneously for a set of representative resin-composites.

METHODS

Six commercially available resin-composites with different filler loadings were selected. A modified bonded-disk instrument that includes temperature-monitoring apparatus was used to measure simultaneously: shrinkage strain, exotherm, and CTE. Shrinkage strain and temperature of disk specimens (n=3/materials) were monitored for 1h after irradiation for 20s at 1200mW/cm(2) (energy density=24J/cm(2)). Disks were irradiated for a second time 60min after the first irradiation. Axial expansion strain and temperature were monitored for 3min. Exotherm was obtained from differences between temperature rise during 1st and 2nd irradiations. CTE was calculated from disk axial expansion due to irradiation heat (ΔL) and rise in temperature (ΔT) during the second irradiation.

RESULTS

The final shrinkage strain values ranged from 1.7% to 2.34%, exotherm values ranged from 4.66 to 9.43°C, and CTE ranged from 18.44 to 24.63 (10(-6)/°C). Negative correlations were found between filler loading and shrinkage strain, exotherm, and CTE. Positive correlation was apparent between shrinkage strain and CTE.

SIGNIFICANCE

The modified bonded-disk instrument could be used to measure simultaneously shrinkage strain, exotherm, and CTE of resin-composites.