Dual cure composites: Could body temperature offset the absence of light activation?

Abstract

Dual cure composites contain both chemically and light-induced polymerization initiators, taking advantage of both processes; however, some studies have suggested that in order to obtain a complete polymerization of the sample it is necessary to light activate the material. Indeed, there is controversy in the literature about the effective polymerization of dual composites in deeper cavity, where light can be strongly attenuated. On the other hand, other studies hypothesized that light activation could determine a rapid increment of the viscosity of the material, blocking the movement of free radicals and avoiding a perfect polymerization. The aim of this study is to evaluate through the thermal analysis and thermogravimetry if dual composite samples, cured only by chemical reaction for 1 h at body temperature of 37 °C, are characterized by the same properties of samples light cured for 40 s at room temperature. The thermogravimetric curve (TGA), the differential thermal analysis and the first derivative of loss of mass (DTG) have been analyzed. The average temperature at which 5% of mass loss occurred and the percentage of the average mass loss between 250 and 350 °C have been recorded. Results have shown that both groups were characterized by a similar thermal stability, compatible with a good polymerization degree and no statistically significant differences have been found.