Comparison of degree of conversion for light-cured and additionally heat-cured composites

The purpose of this study was to compare the changes in the degree of conversion in the various layers of composites after additional heat curing. Four types of composites and three types of inlay ovens were used in this study. Composite was placed in a 4 mm thick Teflon mold and light cured from the top for 60 seconds. Twenty samples were prepared for each composite; 10 of these were additionally heat cured in an inlay oven as the manufacturer recommended. After light curing or light and heat curing, the samples were sectioned into four parts and assigned to groups A, B, C, or D according to their distance from the light source. These sections were then thinned to 50 to 70 mm, and these wafers were analyzed with a Fourier Transform Infrared spectrometer to determine the degree of conversion. A standard baseline technique was used to calculate the degree of conversion. When the composites were heat cured, significant increases in the degree of conversion were noted throughout the samples, but the amount of increase differed among materials. Thus the clinical performance of a heat-treated composite inlay may be different depending on materials.