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Abstract Our study aimed to investigate the effect of adding a different concentration of silver nanoparticles on impact strength, transverse strength, fracture toughness, surface roughness, hardness and water sorption of heat-cured acrylic resin. According to literature, silver nanoparticles were used in this study due to its ductility, electrical and thermal conductivity, and antimicrobial activity. (174,175) silver nanoparticles were reported to have antimicrobial effects on many microorganisms. In addition to, silver nanoparticles have the potential to impart ‘mechanical properties’ to some dental materials, (179) Silver nanoparticle was incorporated to heat cured acrylic resin in four different concentrations of silver nanoparticles 0.5wt%, 1wt%, 2wt%, 3wt%. Heat cured acrylic resin/ silver nanoparticles complex was cured in boiling water for 25 minutes. The following properties were tested: impact strength, transverse strength, fracture toughness, surface roughness, Vicker’s microhardness as well as water sorption. Impact strength was measured using Izod impact tester model CS- 137. Each notched specimen was held as a vertical cantilever beam. It was broken by a single swing of the pendulum with impact line above the notch and on its same side.Transverse strength was tested by subjecting rectangular specimens to 3-point loading test using the universal testing machine. The load was applied at the centre of the specimen till fracture. Fracture toughness was tested by a single edge notch specimen using the three-point loading using the universal testing machine (Instron® Bluehill Lite Software). The notch was directed downward and the load was applied in the middle of the specimens up to fracture and fracture toughness was calculated. Surface roughness was tested by a circular discs specimen. The surface roughness was tested using a profilometer (TR100 surface roughness tester, time group Inc. USA.). It is based on measuring the Ra value which is Arithmetic mean of the movement of the profile above and below the central line of the surface. The mean of five tracing for every specimen was been calculated and taken as the surface roughness value of the specimens. Vicker’s microhardness was measured using a microindentation tester (Model VHS-50, Laizhou Huayin Testing Instrument Co., Ltd. China) with a Vicker’s diamond pyramidal indenter having a square base and 136° pyramidal angle attached to a universal research microscope. The specimens were individually positioned in such a way that the test surface was kept perpendicular to the indentator.Water sorption was measured by drying the circular specimens at 37±2 °C for 24 hours in a desiccator containing thoroughly dry anhydrous silica gel. The specimens were then weighed with sensitive balance capable of measuring. The discs were then immersed in distilled water at 37 °C for 7 days. After a week the specimens were removed from the water and weighed again. Water sorption was calculated in the unit of mg/cm2. By observing the data obtained from impact strength test of the present study, our results showed a significant increase in the impact strength of the 0.5wt% and the 1wt% silver nanoparticle modified groups in comparison to the control group. However, the 3wt% silver nanoparticle modified group showed a significant decrease differences. While, the 2wt% silver nanoparticle modified group showed no significant differences in comparison to the control group. By observing the data obtained from transverse strength test of the present study, our results showed no significant in the transverse strength of the 0.5wt% and the 1wt% silver nanoparticle modified groups in comparison to the control group. While, the 2wt% and the 3wt% silver nanoparticle modified groups showed a significant decrease differences compared to the control group. By observing the data obtained from the fracture toughness test of the present study, our results showed a significant increase in the fracture toughness strength of the 0.5wt% silver nanoparticle modified group in comparison to the control group. However, the 1wt% and the 2wt% silver nanoparticle modified groups showed no significant differences in comparison to the control group. Furthermore, the 3wt% silver nanoparticle modified group showed a significant decrease differences in comparison to the control group. By observing the data obtained from surface roughness test of the present study, our results showed a significant decrease in the surface roughness between all nanosilver modified groups in comparison to the control group. 0.5wt% silver nanoparticles modified showed the least significant difference, followed by the 1wt%, 2wt%, and then the 3wt% silver nanoparticles modified groups in comparison to the control group. Our results for vicker’s microhardness showed a significant increase between all nanosilver groups in comparison to the control group. The 0.5wt% silver nanoparticles modified group showed the highest significant difference, followed by the 1wt%, 2wt%, and then the 3wt% silver nanoparticles modified groups in comparison to the control group. By observing the data obtained from water sorption test of the present study, our results showed a significant increase in the water sorption between all nanosilver modified groups in comparison to the control group. The 0.5wt% silver nanoparticles modified showed the least significant difference,followed by the 1wt%, 2wt%, and then the 3wt% silver nanoparticles modified groups in comparison to the control group. Regarding the results of our study, the 2wt% and the 3wt% silver nanoparticles modified groups showed the lowest significant mean values in comparison with the control group in impact strength, transverse strength, fracture toughness as well as microhardness. Finally, within the limitations of the present study, we can conclude that the incorporation of silver nanoparticles in heat-cured acrylic resin had a great influence on the mechanical as well as physical properties. |