Polymerization Shrinkage of Restorative Resins Using Laser and Visible Light Curing

Abstract

This in vitro investigation compared the amount of linear shrinkage that occurs when a light-cured composite resin is cured with a visible light source, and also with an argon laser. When composite resins are light-cured, they undergo a certain degree of polymerization shrinkage, which can be clinically significant and affect the efficacy of the restoration. A new protocol utilizes laser curing instead of conventional visible light. Two hybrid composite resins were used, Z100 and TPH-Spectrum. Dimensional change was measured in a linear direction, using a calibrated light-microscope. A total of 40 samples of composite resin was tested using two curing lights, and two hybrid composite resins, resulting in four groups of 10 samples (n = 10) each. According to manufacturer instructions, curing time for the laser was 10 sec, and for visible light was 40 sec. With TPH-Spectrum, the mean shrinkage with visible light was 0.583% compared to that with laser light which was 0.591%. With Z100, the mean shrinkage with visible light was 0.565%, compared to that with laser light which was 0.551%. There was no significant difference in amount of shrinkage of hybrid composite resins between using visible light or laser light. There was also no significant difference in shrinkage between the two hybrid composites for either light source.