AN INVESTIGATION INTO THE MICROHARDNESS OF A LIGHT CURED COMPOSITE WHEN CURED THROUGH VARYING THICKNESSES OF PORCELAIN

An investigation was carried out to measure the completeness of cure of samples of a composite resin, light cured for 40s and 60s through porcelain discs of varying thickness. Once cured, each specimen was subjected to Vickers microhardness testing to assess the completeness of cure. Composite resin specimens cured without an intervening porcelain disc were used to establish a baseline. The results showed that increasing the thickness of the porcelain disc produced a statistically significant decrease in microhardness of the composite resin. Increasing the cure time from 40s to 60s produced a significant increase in microhardness. The increase in microhardness with increased cure time was more pronounced when the discs of thickness 1 mm and 2 mm were used, and when there was no overlying porcelain disc. Copyright © 1990, Wiley Blackwell. All rights reserved