Slowing-down of Polymerization Reaction by Modulating CQ and EDMAB

Objectives: Slowing down the polymerization reaction can reduce contraction stress attributed to polymerization shrinkage without a detrimental influence on the ultimate degree of conversion under certain conditions. The objective of this study was to evaluate the effects of modulating the concentration of camphorquinone (CQ) and ethyl (4-dimethyl amino) benzoate (EDMAB) on the degree of conversion and the rate of polymerization using a differential scanning calorimetry (DSC) in visible light cured resins and resin composites. Materials and Methods: Nine experimental resins and nine composites were made based on Bis-GMA/UDMA/TEGDMA with different concentration of CQ (0.1/0.4/1.6 wt %) and EDMAB (0.05/0.2/0.8 wt %). In composite series, the resins were made of composite by adding silanized glass filler to the monomer mixture. Light curing was performed by Optilux 501 (800 mW/cm2, Kerr, USA) for 60 s. DSC curves were obtained for 19 min at 25°C isothermal condition by DSC 7 (Perkin Elmer Norwalk, CT, USA). Using the exothermic heat values from these DSC curves, the degree of conversion and rate of polymerization were calculated. Results were analyzed by ANOVA and Tukey's studentized range test (p<0.05). Results: In resin groups, polymerization reaction was slowed down with less CQ and EDMAB, while the degree of conversion was not influenced with CQ except at 0.01 wt% of EDMAB. In composite groups, polymerization reaction was slowed down with less CQ and EDMAB, while the degree of conversion was not significantly influenced with the concentration of EDMAB. The combination of 1.6 wt% of CQ and 0.01 wt% of EDMAB showed slower polymerization reaction than other combination without hampering the degree of conversion. Conclusion: This study suggests that there is certain combination of CQ and EDMAB in their concentrations that has slow polymerization reaction without hampering the degree of conversion.