Effects of Adding TiO2 Nanoparticles on Flexural Strength and Hardness of Two New Commercial Flowable Dental Composites

Introduction The present study aimed to investigate the effect of adding TiO2 nanoparticles on the flexural strength and hardness of two dental composites. Methods: TiO2 nanoparticles were prepared and added to two flowable dental composites (Beautifil Flow Plus and Clearfil AP-X Flow) at 0, 0.2, 0.5, and 1% (w/w) which was confirmed by SEM and TEM analysis. Mixing was manually performed using Lentulo Spiral Paste Carrier. The specimens were divided into 8 groups of 10 according to the type of composites and different concentrations of TiO2 nanoparticles. Bar-shaped specimens (2×2×25 mm) were fabricated in a half-split stainless steel mold and cured for 40 s by an LED curing system. Flexural strength was evaluated using a universal testing machine. Surface microhardness was also measured by the Vickers microhardness tester. Results: For the two tested composites, flexural strength increased by 0.5% TiO2 nanoparticles concentration. The flexural strength of Clearfil AP-X Flow combined with 0.2, 0.5 and 1% TiO2 nanoparticles were 112.54±12.87 (P 0.05), 114.62±8.14 (P 0.05), and 99.92±6.23 (P 0.05), respectively. Also, for Beautifil Flow combined with 0.2, 0.5 and 1% TiO2 nanoparticles were, 92.21±4.26 (P 0.05), 94.05±5.36 (P 0.05) and 74.17±9.43 (P 0.05), respectively. Conclusion: Adding TiO2 nanoparticles to Clearfil AP-X Flow composite decreased the hardness; however, adding TiO2 nanoparticles by 1% concentration increased the surface hardness of Beautifil Flow and reached its maximum value. Also, TiO2 nanoparticles at very low concentrations enhance the flexural strength of dental flowable composites.