Introduction: Recently, nanoparticles such as nano-TiO2 have been added to some dental materials for enhancing dental carries prevention due to their antibacterial activity. Aim: This study aimed to assess the shear bond strength of a self-adhesive composite containing TiO2 and SiO2 nanoparticles for orthodontic bracket bonding. Materials and methods: This in vitro, experimental study was done on 70 extracted human premolars divided into 7 groups. Six groups of Vertise Flow self-adhesive composite samples were prepared: without any nanoparticles, with 0.5% and 1% TiO2 nanoparticles, 0.5% and 1% SiO2 nanoparticles, and 1% mixture of TiO2 and SiO2 nanoparticles so that nano-hybrid composites were prepared. Metal brackets were bonded with these samples as well as Transbond XT as the control group. The shear bond strength of the brackets to enamel was measured using a universal testing machine. The adhesive remnant index (ARI) score was also determined by a stereomicroscope. Data were analyzed by one-way ANOVA, Tukey&rsquo;s test and Kruskal-Wallis test. Results: The shear bond strength of the groups was significantly different (p=0.000). Pairwise comparisons revealed that the bond strength of Transbond XT group was significantly higher than others (p<0.05), followed by the 1% TiO2 group with significant differences with Vertise Flow and 0.5% TiO2 groups. The lowest value belonged to Vertise Flow with no nanoparticles. The ARI scores was different in the control group (p=0.000). Conclusions: Adding TiO2 and SiO2 nanoparticles to Vertise Flow self-adhesive composite not only did not adversely affect its shear bond strength, but also slightly increased it. Overall, the self-adhesive nano-hybrid composite containing TiO2 and/or SiO2 nanoparticles, following an additional etching step would be acceptable for bracket bonding and can be used clinically to benefit from the antimicrobial activity of these nanoparticles.

SummaryThis study developed a new adaptive design for a divergent fluid wall damper (DFWD). This design decreases the dynamic vibration in reinforced concrete (RC) structures subjected to dynamic forces caused by earthquakes, wind, tsunamis, and explosions. The DFWD comprises a tank connected to the lower floor that is filled with a fluid and a plate with fins located inside the tank connected to the upper floor. The DFWD uses a bypass system mechanism that circulates fluid inside the wall damper tank through a divergent pipe and controls the fluid pressure during vibration using a double-acting valve. To evaluate the performance of the DFWD in RC-frame structures, we fabricated and experimentally evaluated a prototype of the device based on a new adjustable design. Two RC frames, a bare frame and a frame with DFWD, were cast with the same geometric specifications. These frames were then examined in terms of the time history of applied displacement with a maximum amplitude of 40 mm under the same conditions. The valves in the design of the DFWD were adjustable, and the fully open valve condition was examined. The results indicated that the failure capacity of the frame was significantly improved compared to that of the bare frame as the DFWD absorbed more dynamic force.The ductility of the RC-frame structure equipped with the DFWD was improved by almost 17.8% compared to that of the bare frame. | INTRODUCTIONDesigning earthquake-resistant buildings is a key challenge for structural engineers. Over the past three decades, studies have been performed to improve the seismic design of structures, and different vibration control technologies have been used to achieve safe and economical designs. Energy dissipation devices have been used extensively as external devices to absorb and release dynamic loads in earthquake engineering.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

This article presents the development of new adjustable and adaptive designs of divergent fluid wall dampers (DFWDs) that can diminish the effect of earthquakes on framed structures. The concept and mechanism of DFWDs is based on the bypass system, which is made by controlling the fluid flow inside the wall damper container using bypass pipes and by controlling the fluid pressure through a double-acting valve. The prototype of the DFWD device is fabricated based on a developed design, and the performance of the DFWD installed in steel frames is evaluated through experimental tests. For this purpose, three steel frames with the same geometric specifications are casted and tested in equal conditions, which include bare frame (BF), braced frame (BrF), and frame equipped with DFWD. All specimens are subjected to dynamic cyclic load and the response of the DFWD is evaluated when the valves are 100% open, 50% open, and 100% closed in comparison with the BF and BrF system to assess the performance of the DFWD in various conditions. The results indicate that the frame furnished with the DFWD in all conditions of fully open, half-open, and fully closed valves were able to absorb and dissipate more force than the BF by almost 28%, 53%, and 73%, respectively.