Determination of curing heat and curing time of light-cured composite resins by differential scanning calorimetry

Abstract

The behavior of curing heat of in light-cured restorative composite resins, containing bis-GMA and 3G, was investigated by differential scanning calorimetry (DSC). Visible light-activated polymerization of these monomer systems was studied using camphorquinone (CQ) and dimethylaminoethyl methacrylate (DMAEMA) as reducing agent. In particular, DSC can be easily used to measure the heat of polymerization because of the easy features in the sample preparation. Four samples of a visible lightcured restorative composite resin (two of them unfilled and two filled) were studied at two different light exposition times. The used materials in this study were bis-GMA, 2,2-bis[p-g-methacryloxy-b-hydroxypropoxy)phenyl]- propane; 3G, triethylene glycol dimethacrylate; CQ, camphorquinone and DMAEMA, dimethylaminoethyl+methacrylate. The two filled composites were prepared with silicium dioxide (77 wt %, 30 µm particle size average). A system of thermal analysis Mettler TA-3000, DSC-30 was used to carry out measurements, in an isothermal segment at 37 oC during 5 min under a controlled thermal program. The specimens were polymerized by illuminating them in a DSC apparatus with radiation from a visible light source (Heliolux II) for 0.33 and 0.67 min and the heat output was determined. It seems that the exothermic peak of the DSC curve for lightcured resins depend on the heat of polymerization of each monomer itself contained in the resins.