Evaluation of the effect of different light sources on the conversion rate and mechanical and surface properties of bulk-fill composites

Introduction and Aim: The aim of our study is to evaluate the effect of different light sources on the C=C conversion degree of bulk-fill composites and to examine the effect of the conversion degree on the mechanical and surface properties of the composite. Materials and Methods: In our study, 3rd generation LED device (Valo) light of different application modes (soft, hard) and halogen (QTH) light to be polymerized with different content 3 high-viscosity bulk-fill composite resin (Tetric EvoCeram, Beautifil, Espe Filtek) and 1 nano-hybrid resin composite (GrandioSO) has been used. In order to determine the degree of transformation, mechanical and surface properties of composite resins polymerized with different light sources, a total of 60 samples were prepared in metal molds with a diameter of 5 mm and a depth of 4 mm, 5 samples in each of the subgroups to be measured in each composite material (n=5). The degree of conversion was measured by Raman spectroscopy, and the stiffness and modulus of elasticity were measured by Nanoindenter. In addition, the surface roughness of the materials was measured with SPM and the surface properties were visualized with SEM/EDS. While evaluating the findings obtained in the study, IBM SPSS Statistics 22 program was used for statistical analyses. The data obtained were evaluated by three-way analysis of variance (3-way ANOVA test) and Turkey HSD test was used for post hoc analyses. Results: Averages of conversion degrees of composite resins polymerized with different light sources Tetric N-Ceram > GrandioSO > Beautifil > Filtek Espe. The mean conversion degree of the composites polymerized by halogen light source was found to be significantly higher compared to the soft mode of the LED (VALO) light device. (p=0,00) There was no significant difference in the degree of conversion among other light sources (p>0,05). The degree of transformation, hardness and modulus of elasticity averages of bulk fill composite resins at 0 mm depth were found to be significantly higher than 4 mm depth (p=0,011). As a result of the analyses performed with the nanoindenter device, hardness and modulus of elasticity averages of the composites polymerized with different light sources were found to be Beautiful > GrandioSO, Filtek Espe and Tetric N-Ceram > GrandioSO, Filtek Espe (p=0,426). There is no significant difference between other composites (p>0,05). The effect of different light sources on the stiffness and modulus of elasticity of the composites was not statistically significant (p>0,05). It was observed that the surface roughness averages in all light sources were listed as GrandioSO > Filtek Espe > Tetric N-Ceram > Beautifil. No statistically significant relationship was found between the degree of transformation and mechanical and surface properties of different composites polymerized with different light sources (p>0,05). Conclusion: A new generation of bulk fill composites has shown a degree of polymerization conversion above the clinically acceptable value at recommended thicknesses with all light sources. The mechanical and surface properties of composite resin materials can be affected by many factors such as the organic matrix, filler type and ratio, as well as the properties of the light sources used in polymerization depending on the type of photoinitiator it contains.