Conversion, Polymerization Shrinkage, Heat Generation, and Depth of Cure of Novel Dental Composites

Abstract

This study aims to determine the conversion, polymerization shrinkage, heat generation, and depth of cure of novel dental composites, and compare with current commercial composites. Methods: A total of 24 different formulations were tested for their conversion, shrinkage, heat generation, and depth of cure. Conversion was determined by using FTIR. Polymerization shrinkage and heat generation were determined theoretically using conversion, monomer volume fraction, average molecular weight of monomers present in each formulation, and number of methacrylate groups present in each monomer. Depth of cure was determined using the ISO 4049 scraping test.Results: The values obtained in this study for shrinkage, and heat generation were comparable to commercial bulk filled composites Z250, and Gradia. The factors that reduced the shrinkage and heat generation to a greater extent were sample thickness, and CaP addition. The higher shrinkage and heat generation in thin samples can be explained by large number of photons on the top surface. The heat generation is affected by the same variables as that of conversion and shrinkage. The heat generation values for samples using conversions at a thickness of 4 mm were ~ 0.06 kJ/cc, while using 1 mm thickness values gave ~ 0.08 kJ/cc. The reduction in depth of cure with the addition of CaP was ~ 5 %.Conclusion: The relatively higher, or comparable degree of conversion for experimental composites than commercial materials, could indicate their greater suitability for clinical applications. Polymerisation shrinkage, and heat generation are directly related to conversion, and conversion is affected by depth (thickness) of composites More detailed analysis is needed to confirm the ultimate depth of cure of these materials.