Studies On The Properties Of A Polymerized Dual Action Antimicrobial Nanocomposite Modified Resin Matrix

Objectives:The aim of this study was to investigate the antibacterial characteristics of a novel polymerized dual action antimicrobial nanocomposite-AgBr/BHPVP against oral pathogens,and then to determine the antibacterial activity and mechanical properties of AgBr/BHPVP modified resin matrix.Meanwhile,the cytotoxicity to human dental pulp cells(HDPCs)of AgBr/BHPVP and the eluent of AgBr/BHPVP modified resin matrix were also determined,thus providing a reference for its application in dental restorative materials.Methods:The minimal inhibitory concentration(MIC)and minimal bactericidal concentraion(MBC)of AgBr/BHPVP against six strains of oral bacteria were tested using a broth dilution test.Extended antibacterial and antifungal testings were performed to clarify the potent long-lasting antibacterial and antifungal properties of AgBr/BHPVP against Streptococcus mutans UA159(S.mutans)and Candida albicans ATCC90028(C.albicans).At the same time,Ag+ release from AgBr/BHPVP at the 1st?2nd?3rd?5th?7th?9th?12th?14th day was detected by an inductively coupled plasma-mass spectrometry(ICP-MS).Bactericidal kinetics testings were also performed in order to examine the time-kill kinetics of AgBr/BHPVP against S.mutans and C.albicans at the concentrations of 4×?2×?1×MBC,respectively.Bacterial morphology were observed by a field emission scanning electron microscope(Fe-SEM).The cytotoxicity to HDPCs of AgBr/BHPVP and the daily release of Ag+ from AgBr/BHPVP were also determined by a WST-8 assay.AgBr/BHPVP was incorporated at 0.5%?1.0%?1.5%(by mass)into a Bis-GMA/TEGDMA resin matrix,which were used as modified groups.Bis-GMA/TEGDMA without incorporation of AgBr/BHPVP served as control group.At the same time,three middle control groups-0.13%AgBr(MA),0.87%BHPVP(MB),and 0.13%AgBr+0.87%BHPVP(MA+B)groups were set up in order to compare their antibacterial activities with 1.0%AgBr/BHPVP groups.The colony forming unit(CFU)of S.mutans on the resin specimens before and after 3-month aging were quantified,and their survival status was observed by a confocal laser scanning microscopy(CLSM).Flexural strength(FS)and Vickers microhardness number(VHN)were measured by universal testing machine and vickers hardness tester,respectively.The cytotoxicity to HDPCs of eluent of AgBr/BHPVP modified resin matrix was determined by a WST-8 assay.Results:AgBr/BHPVP showed certain bactericidal activity against the six tested strains of oral bacteria.The MIC values of AgBr/BHPVP ranged from 19.53 to 156.25?g/ml,and the MBC values of AgBr/BHPVP ranged from 39.06 to 156.25 ?g/ml.The MIC and MBC values of AgBr/BHPVP was significantly lower than those of BHPVP(P<0.05).AgBr/BHPVP was bactericidal against S.mutans and C.albicans at a concentration of 625.00 ?g/ml for the 14th observed inoculation,and it sustained a sufficient and stable concentration of Ag+ ions in the broth for days.Bactericidal kinetics testings indicated that AgBr/BHPVP had rapid killing effects against S.mutans and C.albicans at the concentration of their 4xMBC,respectively.No viable bacteria was detected after 30 min incubation with S.mutans and 240 min incubation with C.albicans.The bactericidal speed at the concentration of 4xMBC was higher than that of 2×?1×MBC.The Fe-SEM images revealed that AgBr/BHPVP could destroy the integrity of bacteria and fungi.The median lethal concentration value(LC50)toward HDPCs in the presence of AgBr/BHPVP was between 100 and 200?g/ml,a value greater than that of Bis-GMA.The RGR of HDPCs in the presence of the daily released Ag+ from AgBr/BHPVP ranged from 92.59 to 79.51%.The CFU of S.mutans on resin specimens of 1.0%AgBr/BHPVP modified groups were significantly lower than those of control groups before or after 3-month aging(P<0.05);The CFU on resin specimens of 1.0%AgBr/BHPVP modified groups had no significant difference between before and after 3-month aging(P>0.05).The CFU of S.mutans on resin specimens of MA and MB groups were significantly higher than that of 1.0%AgBr/BHPVP groups(P<0.05),while there was no significant difference between MA+B and 1.0%AgBr/BHPVP groups before aging(P>0.05).The CFU of MA,MB,and MA+B groups were significantly higher than that of 1.0%AgBr/BHPVP groups after 3-month aging(P<0.05).Observation under CLSM revealed that alive bacteria on resin specimens of modified groups were significantly less than those of control groups.The value of FS of 0.5%and 1.0%AgBr/BHPVP modified groups had no significant difference comparing with the control group(P>0.05),but the value of FS of 1.5%AgBr/BHPVP modified group was significantly lower than that of the control group(P<0.05).There was no significant difference in the value of VHN between the four groups(P>0.05).The RGR of HDPCs in the presence of the eluent of 1.5%AgBr/BHPVP modified resin matrix was 72.42%before aging,and the RGR of HDPCs in the presence of the other modified groups ranged from 75 to 99%.Conclusions:AgBr/BHPVP had potent,long-lasting,and efficient bactericidal activity against the tested oral bacteria,and it could destroy the integrity of bacteria and fungi cells.The cytotoxicity of AgBr/BHPVP to HDPCs was lower than that of Bis-GMA.AgBr/BHPVP modified resin matrix had stable and lasting antibacterial activity against S.mutans,and the antibacterial activities of cured resin matrix incorporated with AgBr/BHPVP increased with the incorporated concentration increased.moderate AgBr/BHPVP modified resin matrix had certain antibacterial property to S.mutans before and after 3-month aging,and mechanical properties of resin matrix were not affected significantly,and it has low cytotoxicity to HDPCs.