The Effect Of Polymerized Core Shell AgBr/cationic Polymer Nanocomposite On Pit And Fissure Sealing And The Regulation Of MMPs Activity

Objective:This study was aimed to evaluate the effect of silver bromide/cationic polymer nanocomposite(AgBr/BHPVP)on the antibacterial activity and mechanical properties of a pit-and-fissure sealant and the activity of soluble recombinant human matrix metalloproteinases(MMPs)(rhMMPs)and Matrix-bound endogenous MMPs.Methods:AgBr/BHPVP(0.5%,1.0%,or1.5%wt)was respectively incorporated into a commercially available sealant,resin-based pit-and-fissure sealant(3MTM,ESPETM,ConciseTM);the same sealant,ConcisenTM,without AgBr/BHPVP was served as a negative control,and ClinproTM Sealant(3MTM,ESPETM),a fluoride-releasing resin,was used as a positive control.Colony-forming unit counts(CFU)and metabolic tests,field emission scanning electron microscope(Fe-SEM)and confocal laser scanning microscopy(CLSM)were applied to evaluate the effects of the cured sealants on the growth of Streptococcus mutans.While the mechanical properties of the cured sealants were determined according to microhardness,degree of conversion and microleakage tests.Inactivation effects of AgBr/BHPVP at different concentrations on soluble recombinant human MMPs(rhMMPs)were evaluated using a colorimetric assay kit.Matrix-bound endogenous MMPs activity was evaluated via dry mass loss and C-terminal cross-inked telopeptide(ICTP)release of demineralized human dentin.Demineralized dentin beams or powder were respectively pretreated with 0.2%chlorhexidine(CHX)or AgBr/BHPVP at different mass%.Changes in ICTP release were examined after 3,5 and 7 days,and loss of dry mass was measured after 30 days.Besides this,gelatin zymography was also used to evaluate the effects of different pretreated groups on MMP-2 and MMP-9.Results:Compared with the negative control and positive control,the cured AgBr/BHPVP-incorporated pit-and-fissure sealant exhibited a significant inhibitory effect on the growth of S.mutans according to CFU and metabolic tests(P<0.05).The Fe-SEM and CLSM images demonstrated that the specimens of the negative control and positive control groups with or without aging were fully covered by primarily live bacteria,whereas the AgBr/BHPVP-incorporated sealant with or without aging showed a lower density of cells and a greater proportion of dead bacteria when compared with the other groups.Moreover,there were no significant differences in the microhardness,degree of conversion and microleakage among the AgBr/BHPVP group,the negative control and positive control groups(P>0.05).AgBr/BHPVP exhibited inactivation function on soluble MMP,with about 90%of inhibition on rhMMP-2,rhMMP-8 and rhMMP-9 at 1.5%AgBr/BHPVP concentration.Compared with control group and CHX group,AgBr/BHPVP pretreated demineralized dentin exhibited the lowest ICTP release after 7 days(F=65.389,P<0.001).Dentine beams incubated in 1.5%AgBr/BHPVP showed only(4.3 ± 0.98)%loss of dry mass vs.(16.34 ± 3.60)%loss for control.Except for AgBr group,other pretreated groups had obvious inhibition on gelatinase activity in gelatin zymography.Conclusion:Sealant incorporated with a moderate amount of AgBr/BHPVP had stable and lasting antibacterial activity against S.mutans,Therefore,AgBr/BHPVP-containing pit-and-fissure sealant shows promising applications for preventing or controlling dental caries on occlusal pit and fissures of molars.The AgBr/BHPVP is effective in inhibiting activities of both soluble and matrix-bound MMPs.AgBr/BHPVP may have the potential to be used in dental materials and improve the resin-dentin bonding durability.