| Resin based materials were reported to accumulate more dental biofilm than other restorative materials when they were used in the oral cavity for a long period of time,which would causing dental caries.At present,many new kind of antibacterial agents have been applied to the prevent dental caries.However,these researches focused more on improving the antibacterial ability,while sacrificing the mechanical properties and biocompatibility of dental resins.Therefore,it is a hot topic to endow resin base dental restorative materials innovative antibacterial properties for inhibiting the formation of dental plaque biofilm,preventing the secondary caries and other infections,meanwhile improving the mechanical properties and biological safety.Antimicrobial nanocomposites attracted extensive attention of scientific researcher due to their strong antibacterial activity,high stability and weak toxicity.As compared with common antibacterial agents,they present more superior physic,chemical,mechanical performance.If the antimicrobial nanocomposites are incorporated into dental resins as nano-filler at low concentration,they are expected to exert excellent antibacterial properties to inhibit the formation of plaque biofilm without causing decrease of biocompatibility greatly.Besides,the nanoparticles can improve the mechanical properties of resin-based material On this basis,a series of antibacterial nanocomposites have been prepared and were used as antibacterial fillers to build single antibacterial mode,dual antibacterial mode and acid-responsive antibacterial mode of dental restorative material The main research contents and conclusions were summarized as follows:Firstly,cationic polymer functionalized NDs were prepared and the effect of the length of hydrophobic chain on the agglomeration and antibacterial properties was investigated.Introducing a certain mole of HEMA to cationic polymer of modified NDs,not only improved the disaggregation effect and dispersion stability,but also improved the antibacterial properties and biocompatibility of functionalized NDs.The prepared QND-Hio owned the best disaggregation effect with particle size ranging from 10 to 100nm.The MIC values of QND-Hio against Gram-negative bacteria E.coli and Gram-positive bacteria S.aureus were 100 pg/mL and 50?g/mL,respectively.The antibacterial mechanism results showed that due to the formed hydrogen bonding between pendent hydroxyl of HEMA and the phosphate head groups of cell membrane,QND-Hio possessed stronger interactions with the bacterial iipid bilayers,resulting in the membrane-separating destruction of E.coli.Then,photo-curable catio nic copolymer functio nalized nano comp o sites(QNDs)were prepared and copolymerized with Bis-GMA/TEGDMA resins to build contact-killing antibacterial dental materials.The antibacterial fillers were well dispersed in the resins and greatly improved the mechanical properties of the dental resins.The Vickers hardness,flexural strength and modulus of 0.6 wt%QND-incorporated dental rensins were improved 75.1%,46.5%and 48.5%,respectively.The addition of antibacterial nanoparticles not only gave the QND-containing resins a certain antibacterial ability,but also reduced the hydrophobicity,exerting anti-adhesion ability to the modified resins.The results of CCK-8 assay showed that the prepared antibacterial dental resins showed less toxic to macrophage RAW 264.7.In order to further improve the antibacterial properties of QNDs modified resin materials,and avoid the effect of "contact inhibition".Ag/QNDs nanocomposites were prepared by in-situ reduction method on QNDs surface loaded silver nanoparticles,then were copolymerized with the resin matrix to build the dental restorative materials with dual antibacterial mode.The Ag/QNDs nanocomposites still maintained good disaggregation effect and exhibited excellent antibacterial properties,even can killed all E.coli within 90min.By reason of homogeneous dispersion and strong bonding with resin matrix,Ag/QND-reinforced resin exhibited great improvement of mechanical properties.The Vickers hardness,flexural strength and modulus of 0.6 wt%QND-incorporated dental rensins were improved 51.1%,33.7%and 24.9%as compared with pure resins,respectively.Due to the combined bactericidal effect of Ag ions and cationic polymers,1.0 wt%Ag/QND-containing resins could killed 82.1%bacteria.But the cytotoxicity of Ag/QND modified resins were improved as a result of the "sudden release effect" of Ag+.Due to the "sudden release effect" of Ag+,the long-term antibacterial performance of Ag/QND-containing dental resins should be improved.Additionally,the release of Ag+ from silver is subject to the environmental oxygen content.In order to solve above problems,photocurable core-shell AgBr/cationic polymer nanocomposite AgBr/BHPVP was designed and developed.The MIC values of nanocomposites against Gram-negative bacteria E.coli and Gram-positive bacteria S.aureus was 16?g/mL,displaying excellent antibacterial properties.Due to the core-shell structure of the nanocomposites,the stability of AgBr was improved,and Ag+ was able to be "sustained release".The nanoparticles showed less cytotoxicity toward NIH3T3 cells.Then,AgBr/BHPVP were copolymerized with the resin matrix to build the dual antibacterial dental restorative materials with Ag+ sustained release.As a result,incorporation of AgBr/BHPVP nanocomposites did not adversely affect the flexural strength and modulus but greatly increased the Vicker's hardness of resin disks.By reason of the sustained release of Ag+ ions,after four weeks of aging,AgBr/BHPVP-containing resin disks had potent bactericidal activity against S.mutans.Cytotoxicity studies showed that though the macrophage RAW 264.7were incubated on 1.5 wt%AgBr/BHPVP incorporated resins,the survival rate was still more than 80%.Traditional antibacterial dental resin composites usually kill the oral bacteria without selectivity,which might break the balance of oral micro-ecosystem,and even causing bacterial drug resistance.It is well known that dental caries is mainly caused by acids deriving from bacterial fermentation.In this project,a novel acid-responsive antibacterial SiO2 nanocomposites was functionalized with copolymers composed by cationic monomer ADMP,pH-responsive mononer MAA and compatible monomer HEMA.The antibacterial results of the fabricated nano-hybrids showed that they did not exert any bactericidal ability in a neutral or alkaline environment,but presented excellent antibacterial activity at pH=5.5 weak acidic environment The MIC values of ASiO2 against E.coli and S.aureus were 16 ?g/mL.Moreover,the nanocomposites showed high selectivity(HC50/MIC)and almost showed no toxicity toward mouse fibroblasts.Then,the functionalized SiO2 were copolymerized with the resin matrix to build acid-responsive antibacterial dental restorative materials.Due to the high affinity between nano-fillers and resin matrix which resulted from HEMA of nano-filler surfaces,the resin monomers could swell the nanocomposite shells,resulting in the formation of interpenetrating network after photo-curing,which greatly improved the mechanical properties of the modified resins.On normal physiological condition,the surface of dental resin presented bacteria-resistant ability owing to zwitterionic state.When bacterial colonization and biofilm formation occur on the surface,the local environment becomes acidic,which drived the surface to be positively charged due to the protonation of the carboxylic acid group,ultimately activating the bactericidal function.The bacteria-resistant and bactericidal functions can be reversibly switched by pH of oral microenvironment.In addition,compared with pure resins,this acid-responsive antibacterial dental resin is advantageous for cell proliferation with extremely low toxicity and is a promising antibacterial dental restorative material for clinical use. |
PDF Full Text Request