Methods: A LED light curing device (Mectron Spa, Italy) was used. Two light power profiles were distinguished: a conventional continuous power at 1200mW/cm2 for 10s and a profile at incorporating the SLER process. Venus A3 shade (Heraeus, Kulzer, Germany) and Gradia A3 shade (GC Corporation, Japan) specimens were realised according to the small punch tests (ASTM F 2183). The Instron 4204 (Bucks, UK) dynamometer and ANOVA analysis were used to assess differences between samples.
Results: A significant difference (p<0.01) was observed in the strength of composites. The strength of materials polymerised through the SLER process was higher than 20% than that measured using conventional polymerisation. Smoother thermal profiles were recorded for samples cured through the SLER process.
Conclusions: As the power unit of conventional light curing devices is turned off, a fast temperature decrease is observed into the material. Consequently, a fast thermal shrinkage occurs and the filler-matrix interface, as well as the resin-dentin interface, can be damaged. The SLER process allows to smooth this thermal shrinkage thus allowing to relax the stress. The novel light curing process, based on a soft light energy release, enhances mechanical properties of dental composite and it is expected to improve the clinical performance of dental restorations.