Abstract
Objectives Polymethyl methacrylate as the most common material used in denture bases has some problems. The aim of this study was to introduce a new nanocomposite of PMMA to improve flexural strength and antifungal properties. Materials and Methods In this experimental study, AgSiO 2 nanoparticles were prepared, and their characteristics were confirmed by scanning electron microscope and energy dispersive spectroscopy techniques. Then the nanoparticles in the weight ratio of 0.1, 0.3, 0.5, and 0.7% were incorporated to heat-cured PMMA and the control group included no nanoparticles. To measure the flexural strength before and after thermocycling three-point bending test was used. Eight samples per group with dimensions of 65 × 10 × 2.5 mm were used. Antifungal activity against Candida albicans (PTCC 5027) was investigated through colony count method. Statistical analysis was done by SPSS at significance level of p -value ≤0.05. Results The mean flexural strength in groups 0.1, 0.3, and 0.7% was significantly higher than the control. After thermocycling flexural strength of the control group was significantly lower than 0.3 and 0.5% groups. As the concentration of nanoparticles increased the antifungal activity improved ( p < 0.05). Conclusion Addition of nanoparticles AgSiO 2 improved flexural strength and antifungal characteristics of PMMA.
Highlights
Since 19401 polymethyl methacrylate (PMMA) has been the most common material used in denture bases due to its favorable characteristics including esthetic and ease of use and repair; there are some unfavorable characteristics such as low fracture resistance[2,3] and denture stomatitis.[4]
Evaluation of AgSiO2 Nanoparticle The AgSiO2 nanoparticles were examined, and their size and quality were verified by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) method
Point check of nanoparticles showed the purity of silver/silica nanoparticles over 98% (►Fig. 2)
Summary
Since 19401 polymethyl methacrylate (PMMA) has been the most common material used in denture bases due to its favorable characteristics including esthetic and ease of use and repair; there are some unfavorable characteristics such as low fracture resistance[2,3] and denture stomatitis.[4] Denture fracture was one of the most common reasons for denture repair.[2,3] Fractures happen more frequently in dentures since attachments limit the thickness of PMMA5,6 and make it more prone to fracture. The flexural strength has a crucial role in acrylic resins resistance to forces which are induced in oral environment, so evaluation of flexural strength is considered as one of the most important characteristics of mechanical properties of acrylic resin. In some studies, adding different nanoparticles improved the strength of PMMA11-14 and in some others had adverse effect due to accumulation of nanoparticles around each other.[11,14] There are some ways to reinforce PMMA such as the addition of fibers.7-9Further improvements have been made with nanoparticles.[10,11,12,13,14]
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