MEASURING POLYMERIZATION SHRINKAGE OF PHOTO-ACTIVATED RESTORATIVE MATERIALS BY A WATER-FILLED DILATOMETER

A water-filled dilatometer specifically designed for determining the p olymerization shrinkage of photo-activated composite restorative mater ials was used to measure the polymerization shrinkage of three visible light-activated composites. Polymerization shrinkage values ranged fr om 1.82% for P-50 to 2.15% and 2.19% for Herculite XRV and Prisma APH, respectively. Shrinkage data obtained in this investigation were comp ared with the published data, and the factors which affect shrinkage m easurements were reviewed. It was concluded that maintaining a constan t temperature environment (+/- 0.02-degrees-C) for the dilatometer dur ing the shrinkage test was the most critical factor for successful app lication of the dilatometer.