Abstract
The aim of this study was to investigate the effect of light intensity on polymerization shrinkage of resin composites. The five materials tested were Lite-Fil (A) (LFA), Lite-Fil (P) (LFP), Z100, Palfique, (PAL) and Tetric (TRC). Two types of measurements were made to determine the effects of environmental temperature and light intensity. Results were analyzed by two-way analysis of variance (ANOVA) and Newman-Keuls procedure at (P<0.05). The changes in temperature and/or light intensity strongly affected composite shrinkage. The amount of shrinkage for LFP at 100% light intensity in room temperature (23°C) was 1.26% and increased up to 2.29% at 60°C. By raising the temperature to 37°C and dropping the light intensity to 42% (459mW/cm2), the amount of polymerization shrinkage was similar to that with full light intensity, and statistically there were no significant differences between 37°C, 45°C, and 60°C. Lower temperatures and lower light intensities produce lower values of shrinkage. However, if the light intensity is below 28%, higher temperatures (60°C) must be applied to obtain a comparable amount of shrinkage.
Clinical Relevance
Pre-heating composite resin materials at body temperature (37°C) is likely to improve physical properties and compensate any drop of light intensity.
Citation
Elhejazi AA. The Effects of Temperature and Light Intensity on the Polymerization Shrinkage of Light-cured Composite Filling Materials. J Contemp Dent Pract 2006 July;(7)3:012-021.
Effect of light intensity and irradiation time on the polymerization process of a dental composite resin
