The Fundamental Research Of Silver Bromide/Cationic Polymer Nano-composite-modified Poly-methylmethacrylate-based Dental Resin

Objectives:This study aimed to evaluate the antifungal effects,the cytotoxicity and mechanical properties of Silver Bromide/cationic Polymer Nano-composite(AgBr/NPVP)-modified Poly-methylmethacrylate(PMMA)-based dental resin.Methods:The AgBr/NPVP was synthesized by on-site precipitation technique.NPVP was characterized by Fourier Transform Infrared Spectroscopy(FTIR)and 1H nuclear magnetic resonance(1H NMR).AgBr/NPVP was characterized by X-ray diffraction(XRD)and transmission electron microscope(TEM).The particle size of AgBr/NPVP was mensurated by a laser particle size analyzer;The minimum inhibitory concentration(MIC)and the minimum fungicidal concentration(MFC)of unpolymerized AgBr/NPVP against Candida albicans(C.albicans)ATCC90028 were tested using a broth dilution test.Fe-SEM was used to observe the morphological changes of C.albicans ATCC90028 after contacting 1 × MFC AgBr/NPVP suspension for 24 h;Experimental PMMA resin specimens incorporated with different concentrations of AgBr/NPVP were prepared,and their antifungal effects were investigated using direct contact test and live/dead bacterial staining assay.Degree of conversion(DC)and cytotoxicity were tested by FTIR and a WST-8 assay,respectively.Flexural strength(FS),flexural modulus(FM),and microhardness were evaluated using a universal testing machine and a microhardness tester,respectively.Results:AgBr/NPVP was successfully synthesized by on-site precipitation technique,and the particle size was(30.42±2.03)nm.AgBr/NPVP had a certain antifungal activity against C.albicans ATCC90028,and its MIC and MFC values were both 250 ?g/ml.Fe-SEM showed that the integrity of the C.albicans cells was disturbed after contacting AgBr/NPVP(1×MFC)for 24 h;the fungi lost their normal cell morphology,and there were pits and perforations on the surface of the cell membrane;some cells were split into pieces.The antifungal activity was increased with the increase of AgBr/NPVP concentration incorporated in PMMA resin.After 2-week aging,the antifungal ratio of all groups showed a stable trend and the 0.3%group reached more than 80%.Confocal laser scanning microscopy(CLSM)showed that the adhesive and survival fungi on the surface of modified resin were less than those of the control group,and the antifungal activity was increased with the increasing of the amount of AgBr/NPVP added in.AgBr/NPVP-modified PMMA resins were low-cytotoxic towards HDPCs according ISO-standard 10993-5.The DC for all experimental PMMA resins reached more than 70%after 24 h of polymerization.FS and FM were no significant differences(p>0.05)between the experimental and control groups.The microhardness of 0.1%and 0.2%group showed no significant difference(p>0.05)compared with the control group,but when the concentration of AgBr/NPVP reached 0.3%,the microhardness decreased,and the difference was statistical significance(p<0.05).Conclusions:Appropriate AgBr/NPVP modified PMMA resins had antifungal effect on C.albicans ATCC90028,and the cytotoxic,physical and chemical properties were not affected significantly.