In vitro evaluation of color stability and surface roughness of different dual cure bulk-fill composite resin materials

Aim: In our study, we aimed to evaluate the color stability and surface roughness properties of three different dual cure bulk-fill and one light cure bulk-fill composite materials used in pediatric dentistry. Materials and Methods: Samples were prepared by placing each material in 5 mm thick, 6 mm diameter polyethylene molds, taking into account the manufacturer's recommendations. Dual cure bulk-fill composites were used in the experimental group and light polymerized bulk-fill composites were used in the control group. Half of the samples used in the experimental group were left to self polymerization, the other half were light polymerized in accordance with the manufacturer's instructions.(n=10) Samples in the control group were light cured.(n=10) A total of 70 samples were obtained from 3 dual cure bulk-fill composites and 1 light cure composite in the experimental group. Surface roughness was measured after each sample was kept in distilled water at 37°C in the incubator for 1 day. The surface roughness test of the samples was performed with the Hysitron TI 950 TriboIndenter device located in Mustafa Kemal University Technology and R&D Application and Research Center. Then, SEM (JEOL 5500 / OXFORD Inca-X Scanning Electron Microscope) in Mustafa Kemal University Faculty of Science and Letters Research Laboratory was used for surface analysis of the samples. In order to determine the color stability, half of the samples to be used in the experimental group were left to self polymerization and the other half were light polymerized. Samples in the control group were light cured. A total of 105 samples were obtained from 3 dual cure bulk-fill composites and 1 light cure composite in the experimental group. After each sample was kept in distilled water at 37°C in the incubator for 1 day, initial color measurements were made with a spectrophotometer (VITA Easyshade® Advance 4.0 (VITA Zahnfabrik, Bad Sackingen, Germany). Then the samples were randomly divided into 3 groups to be kept in distilled water, sour cherry juice and ice-tea for 1 week. Color measurements of the samples were made by spectrophotometer at the end of 1 week. Color differences were recorded according to the CIEDE 2000 system. Results: Among the composite groups, the least surface roughness was observed in the light polymerized Cention-N composite samples in the experimental group. Among the composite groups, the highest surface roughness was observed in the Fill-up composite samples, which were left to self polymerization. In the Fill-up and Cention-N composite groups in the experimental group, the surface roughness of the samples left to self polymerization and the samples polymerized with light differ statistically significantly (p<0.05). When the surface roughness of the composite groups left to self polymerization was compared among themselves, no statistically significant difference was found (p>0.05). When the surface roughness of the composite groups cured with light was compared, no statistically significant difference was found (p> 0.05). Among the composite groups, the highest amount of coloring was observed in the Fill-up composite samples, which were left to self polymerization and kept in cherry juice. The least coloration among the composite groups was seen in the Cention-N composite samples polymerized with light and kept in distilled water. Conclusion: Based on this information, a decrease in surface roughness and an increase in color stability can be expected as a result of light polymerization of dual cured bulk-fill composites in addition to self polymerization.