Investigation of cytotoxicity and physical properties of bulk fill composites

Purpose: The aim of this study is to study and comparatively examine the surface features, cytotoxicity, heat conductivity features and polymerization shrinkage of new generation bulk fill composite resins Materials and Methods: Five different resins which are named as SDR, Tetric Evo Ceram Bulk Fill (TEC), X-trafil (XTF), Sonic Fill (SF), Filtek Bulk Fill (FBF) are used in this study. The polymerization shrinkage of this composite resins is measured by means of μCT device. For this end, after the bulk fill resins were placed into five cylindrical molds for each group which were 4 millimeters high and 5 millimeters in diameter, they were scanned by means of μCT device. After their first scan was completed, the samples were polymerized by means of LED light device for 20 seconds and then they were rescanned. μCT analysis of the images were performed, and shrinkages following polymerization were calculated. Atomic force microscope (AFM) was used so that surface features of composite resins could be examined. Bulk fill composite resins were placed into the molds which were 4 millimeters high and 5 millimeters in diameter and whose top and bottom surfaces were open and 5 samples in total were prepared for each group. Respectively, nano hardness and roughness of top and bottom surfaces of the samples was measured through atomic force microscope (AFM). Dental pulp stem cells (DPSC) were used in order to study cytotoxicity of bulk fill composite resins. Five composite resin disks from each group which were 5 mm in diameter and 4 mm high were obtained, and cytotoxicity of these composite resins on the 1st, 7th, 14th, and 21st days were examined by means of WST-1 test. For heat conductivity measurements, five composite resin disks from each group which were 5 mm in diameter and 4 mm high were obtained and their heat conductivity capacities at 0 ° C and 70 ° C were measured with Physical Properties Measurement System (PPMS). Results: Among the groups are no statistically significant difference in terms of polymerization shrinkage (p>0.05). The top surface nano hardness values are significantly higher in the group TEC than SF, SDR, FBF ve XTF (p<0.05). When average nano hardness values of top surface are compared with those of bottom surface, nano hardness values of bottom surfaces are significantly less in the XTF group (p<0.05). There are not any significant differences in other groups. There are not any statistically significant differences among the values of top surface roughness in the bulk fill composites which were used in the study (p>0.05). When roughness values of top surface are compared with those of bottom surface in the groups, values of bottom surfaces are significantly more in the SDR group (p<0.05). There are no significant differences in other groups (p>0.05). According to the results of WST-1 experiment; compared to the control group, we observed less cell viability for all groups on 21th days. According to the results of the measurements of heat conductivity, the thermal conductivity in XTF and SF groups at 0º C and 70º C is significantly higher than that in FBF, SDR and TEC( p<0.05). Conclusions: In accordance with these results, even though bulk fill composite resins are advantageous with regard to the fact that they provide easiness of practice, they can be considered disadvantageous in terms of cytotoxicity and polymerization shrinkage.