Dental dimethacrylate-based nanohybrid composite Kalore GC: Kinetic study of its light-curing

ObjectiveThis study investigated the light-curing kinetic of the novel dental dimethacrylate-based nanohybrid composite (Kalore GC). Its organic matrix consists of a high molecular weight monomer called DX 511 as well as the known dimethacrylate monomers bisphenol A ethyl dimethacrylate (Bis-EMA) and urethane dimethacrylate (UDMA).MethodsFour properties were measured: degree of conversion (DC), depth of curing (DOC), polymerization shrinkage (S) and glass transition temperature (Tg) versus curing time. These properties were measured by spectroscopic imaging in Attenuated Total Reflection (ATR-FT-IR), scrape test, density measurements and dynamic mechanical thermal analysis (DMTA), respectively.ResultsAfter 10s of light curing, the DC was 2.50%, DOC 1.86 mm and S 1.48%. The composite cured for 10s showed two Tg; 56.4 °C and 112.8 °C. At this stage, the maximum rate of polymerization was noticed. The curing, however, continued with much lower and decreased rate for up to 100s. There, a maximum DC of about 40% and a maximum DOC of about 3.5 mm were observed. Tg values were raised to 59.5 and 102.3 °C, respectively.ConclusionsWithin the condition of this study, the optimum curing time of Kalore GC seems to be 100 s. The composite light-cured up to 300 s showed two Tg, indicating that this compound still contained unreacted double bonds of C=C and macroradicals, which continued to cure upon heating in DMTA.