Fatemeh Koohpeima - Department of Operative Dentistry, Biomaterial Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran
Mohammad Javad Mokhtari - Department of Biology, Zarghan Branch, Islamic Azad University, Zarghan, Iran
Sajjad Khaksabz - Department of Operative Dentistry, Biomaterial Research Center, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran

Introduction The present study aimed to investigate the effect of adding TiO۲ nanoparticles on the flexural strength and hardness of two dental composites. Methods: TiO۲ nanoparticles were prepared and added to two flowable dental composites (Beautifil Flow Plus and Clearfil AP-X Flow) at ۰, ۰.۲, ۰.۵, and ۱% (w/w) which was confirmed by SEM and TEM analysis. Mixing was manually performed using Lentulo Spiral Paste Carrier. The specimens were divided into ۸ groups of ۱۰ according to the type of composites and different concentrations of TiO۲ nanoparticles. Bar-shaped specimens (۲×۲×۲۵ mm) were fabricated in a half-split stainless steel mold and cured for ۴۰ 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 ۰.۵% TiO۲ nanoparticles concentration. The flexural strength of Clearfil AP-X Flow combined with ۰.۲, ۰.۵ and ۱% TiO۲ nanoparticles were ۱۱۲.۵۴±۱۲.۸۷ (P>۰.۰۵), ۱۱۴.۶۲±۸.۱۴ (P>۰.۰۵), and ۹۹.۹۲±۶.۲۳ (P<۰.۰۵), respectively. Also, for Beautifil Flow combined with ۰.۲, ۰.۵ and ۱% TiO۲ nanoparticles were, ۹۲.۲۱±۴.۲۶ (P<۰.۰۵), ۹۴.۰۵±۵.۳۶ (P<۰.۰۵) and ۷۴.۱۷±۹.۴۳ (P<۰.۰۵), respectively. Conclusion: Adding TiO۲ nanoparticles to Clearfil AP-X Flow composite decreased the hardness; however, adding TiO۲ nanoparticles by ۱% concentration increased the surface hardness of Beautifil Flow and reached its maximum value. Also, TiO۲ nanoparticles at very low concentrations enhance the flexural strength of dental flowable composites.

flowable composite, Nanoparticles, surface hardness, Titanium dioxide