2009 Volume 52 Issue 5 Pages 419-425
The purpose of this study was to assess the polymerization shrinkage characteristics of experimental resin composites. In order to measure the volumetric shrinkage, each material was placed in a mold and extruded into a waterfilled dilatometer. The specimens were then light-irradiated using a curing unit with the power density adjusted to either 100 or 600mW/cm2. For the speckle-contrast measurement, each resin composite was condensed into a glass tube and irradiated. The laser-speckle field was recorded in a digital frame as a function of time. When the power density was adjusted to 100mW/cm2, the average volumetric shrinkage ranged from 1.80 to 3.91%, and when the power density was adjusted to 600mW/cm2, the shrinkage ranged from 3.18 to 5.42%. The speckle-contrast measurements revealed changes in the pastes due to the polymerization of the resin composites that were greater than those obtained with the water-filled dilatometer.
