Evaluation and correlation of depth cure and degree of conversion of bulk-fill posterior restorative composite resins

Background: The problem of composite resin filling is the longer time consumed for incremental application. Bulk-fill composite resins were introduced to the market as substitutes for dental amalgam for restoration of posterior teeth. Objectives: The aim of this study was to evaluate the curing depth and degree of conversion of two bulk-fill composite resins. Materials and methods: . Specimens of specific dimensions were prepared from Glacier and SureFil (universal shade, A2), they classified as bulk-fill composite resins. Depth of cure, degree of conversion at different thicknesses for each material (2,3,4,5 and 6 mm) for each thickness separately. The curing depth was determined by the scrapping method (ISO 4049, 2000). The degree of conversion was measured by the Buker FTIR Spectroscopy. Results: The results indicated that, Glacier composite resin has greater curing depth than that of SureFil composite resin. Glacier composite resin was cured above 6 mm thickness, while SureFil composite resin was cured above 5 mm. In general, the degree of conversion was different at the different thicknesses of the materials. SureFil composite resin showed highest degree of conversion at 3 mm followed by 2 mm thickness, while the lowest degree of conversion was noted at 6 mm thickness. Glacier composite resin has the highest degree of conversion at 3 mm followed by 2 mm thickness, while the lowest degree of conversion was noted at 6 mm thickness. SureFil showed positive correlation between the depth of cure and the degree of conversion. Glacier composite resin showed no significant correlation between the depth of cure and degree of conversion. Conclusions: The studied bulk-fill composite resins, cured up to 5mm to 6mm thicknesses. 2 and 3mm thicknesses adequately polymerized than 4 mm, 5 mm and 6 mm thicknesses. The degree of conversion of 2 mm and 3 mm thicknesses was greater than that of the other thicknesses. There was positive correlation between the degree of conversion and curing depth of SureFil composite resin. On the other hand, Glacier composite resin showed no significant correlation between the depth of cure and degree of conversion.