Changes in surface contour of resin composites after light-curing

To determine the changes in free surface contour and volume of resin composites during light-curing by irradiating on half area of a specimen, using a 3-dimensional profilometer.

Resin composite was packed into a metal mold (9 mm in inner diameter and 2 mm in thickness) after applying a lubricant to the mold. Both sides of the specimens were flattened. Light-curing was done on half area of a specimen for 40 seconds. Then, the entire area of the specimens was cured again with the same irradiation condition. Upper surface profile of a cured specimen in the mold was scanned with a three-dimensional profilometer. The changes in the shape of the free surface of resin composite in a simulated cavity after light-curing were determined as the changes in the height of the material under the condition that the height of the material at the non-irradiated margin was set as a reference point (0 mm). Height was calculated at 0, 2, 4, 6 and 8 mm from the irradiated margin. The elevated volume in the central 1.8 mm-thick section of the specimen was calculated at 2 mm intervals from the irradiated margin with the same reference point. Differences in height and volume by the resin composite were analyzed with repeated measures, one-way analysis of variance at the significance level of 0.05.

Height of the irradiated margin was the height and gradually decreased toward the non-irradiated margin. Surface contour change during light-curing was influenced by the distance from the irradiated margin and the brand of resin composite (P< 0.05). Height at the irradiated margin was 113.2-212.4 microm. Total changed volume, compared with the flat uncured surface, was 8.87-17.27x106 mu3. Contour of free surface varied by the resin composite, but showed similar pattern.