Photocalorimetry of light-cured dental composites.

The reactivity of six light-curable dental composite materials has been examined by a novel technique, photocalorimetry, which permits in situ analysis of photoreactions in opaque cross-linking systems. According to photocalorimetry, the rates of reaction of dental composites decrease in the following order: Uvio Fil, Scintilux 2, Visio Dispers, Visio Fil, Silux, and Prisma Fil. By comparing the heats of reaction of the composites and of the resins, one may assume that at least two types of reactive resins are used in these dental composites: one with a heat of reaction of about 35 cal/g, and others with considerably less reactivity, ranging from 14 cal/g to 25 cal/g. Photocalorimetry allows for a rapid assessment of the rate of polymerization (photospeed) of light-curing dental composites and is ideally suited for the study of kinetics and for optimization of formulations.