Influence of light-curing units on the polymerization of low-shrinkage composite resins.

This study examined the effect of various light-curing units (LCUs) on the polymerization of low-shrinkage composite resins. Two different types of low-shrinkage composite resins (silorane-based and methacrylate-based) were light cured using a quartz-tungsten-halogen (QTH) (HX) unit, a single-peak light-emitting diode (LED) (DM) unit, and a dual-peak LED (GL) unit, respectively. Among the tested LCUs, HX showed the lowest light attenuation within the specimens. Among the specimens, Aelite LS and Venus Diamond showed the highest and lowest light attenuation, respectively. Silorane-based Filtek LS showed the highest degree of conversion both on the top and bottom surfaces. On the bottom surface, Grandio and Aelite LS showed the lowest (4.5-7.1%) and highest (25.0-40.0%) decrease in the degree of conversion compared to their top surface. For different LCUs, within the same resin product, the microhardness was significantly different. The silorane-based composite resin showed significantly less polymerization shrinkage than the methacrylate-based nanofiller-containing composite resins.