The Study Of The Antibacterial Effect Of Silver Nanoparticles Against Apical Periodontitis Related Microbes And The Effect To Periapical Tissue Cells

Apical periodontitis is inflammation about the apical tissue of the roots,which usually is the secondary infection of the pulpitis.It is one of the common diseases in the endodontic department.The symptoms of the apical periodontitis are acute toothache and swelling maxillofacial area,and it is one of the prime reasons of tooth loss in middle aged and elderly people.Today root canal therapy is the traditional and first choice to cure apical periodontitis which includes cleaning,shaping,disinfecting and filling steps.This method can remove infection in the root system and reduce planting of the microorganism,to promote the healing of the apical lesions and repairing of the bone,ultimately attain prevention and remedy of the apical periodontitis.Epidemiological surveys suggest that even if the tooth received the throughly root canal therapy,there is also 4%?15%failure rate.The prime reason of this failure rate is the complexity of the root canal system,which result in that the mechanical root canal cleasing could not eliminate the infected tissues.On the other hand,traditional chemical sterilizer could not kick off all the infection either.It is well-known that silver nanoparticles(AgNPs)have great potential to treat burns,wounds and several different infections caused by pathogenic bacteria.Green synthesis of AgNPs that have environmentally acceptable solvent systems and eco-friendly reducing agents is of great importance.The aim of this work was to synthesize AgNPs using gallic acid as reductant as well as stabilizing agent under ambient conditions,and evaluate their antimicrobial effects against multiple frequent microbes.We explore to utilize the AgNPs in the root canal therapy,as adjuvant drug to eliminate the infection of the root canal system and promote the tissue healing around the root apical area.This study will lay a solid foundation for the utilization of AgNPs in dental clinical treatment.Objective The aim of this work was to synthesize AgNPs with green synthesis using gallic acid as reductant as well as stabilizing agent under ambient conditions.Methods AgNPs were synthesized with a polyphenol reduction method,in which gallic acid was utilized as both a reducing agent and a stabilizer.The characterization was evaluated by UV-vis spectroscopy,transmission electron microscopy(TEM),X-ray diffraction(XRD)analysis,dynamic light scattering(DLS)and Fourier transform infrared spectroscopy(FT-IR)spectra.Results The image of transmission electron microscopy(TEM)showed that SNPs exhibited approximately spherical shape with the average diameter of 13.81±2.21 nm.The absorbance peak of obtained SNPs was sharp with the maximum wavelength of 400.5 nm by ultraviolet-visible(UV-vis)spectroscopy,suggesting the formation of small and highly monodispered SNPs.Conclusion This study provides an environmentally friendly technique for facile synthesis of SNPs with excellent antibacterial potential.Objective The aim of this work was evaluate the AgNPs of antibacterial ability of anti-human multidrug-resistant(MDR)pathogenic microbes,key pathogenic microbes of pulpitis and apical periodontitis,suspicious pathogenic microbes of persistent periapical periodontitis.Meanwhile we explore the mechanism of the antimicrobial ability.This work will lay the foundation for the application of AgNPs in the dental clnical treatment.Methods We first determined the minimum inhibitory concentration(MIC)in batch cultures by varying the concentrations of the synthesized AgNPs.And we evaluated the pretreatment of N-acetyl-L-cysteine(NAC)and L-ascorbic acid,whether if they could influence the antibacterial effects of the AgNPs.Results The antimicrobial potential of the AgNPs was evaluated against multiple common pathogenic microbes.Among them,the gram-negative bacteria exhibited more sensitivity toward AgNPs than the gram-positive bacteria.In addition,the N-acetyl-L-cysteine(NAC),a silver ion chelator,pretreatment could protect the E.coli and P.aeruginosa from the AgNPs inhibition,while the pretreatment of the L-ascorbic acid,an antioxidant against oxidative stress,did not significantly influence the antibacterial effects of the AgNPs.Conclusion The results indicated that the microbial sensitivity to the AgNPs was found to vary depending on the microbial species.And the data suggested that the ionic silver release,but not reactive oxygen species(ROS),played a key role in the antimicrobial effect of the AgNPs.To sum up,this study provides an environmentally friendly technique for facile synthesis of AgNPs with excellent antibacterial potential.Objective The aim of this work was to assess the effect of AgNPs on human periodontal ligament fibroblasts,and to explore the influencing mechanism.Methods We observed the changes of human periodontal ligament fibroblasts after treatment by AgNPs with inverted microscope.And the work evaluated the changes of cell viability,cell apotosisand cell cycle with treatment by AgNPs.Results After different concentration(0?4?8?16?32?64?g/mL)of AgNPs for 24h,human periodontal ligament fibroblasts diminished compared to control in 32?g/mL group,and the cells in 64?g/mL group changed obviously,the spindle shape changed into round or irregular shape.And the volume of the cells shrinked obviously.The cell viability did not changed much when the concentration was within 32?g/mL and the time within 48h.But the cells in 64?g/mL group changed obviously regardless of the treatment time.And cell numbers in G1 phase increased,G2 phase decreased when AgNPs'concentration was 32?g/mL for 24h treatment time.AgNPs with the concentration under 32?g/mL did not change the cell cycle and apoptosis.Conclusion In the work,AgNPs with low concentration will not induce apoptosis and change cell cycle,and will not change the shape of the human periodontal ligament fibroblasts.But with the concentration increasing,and the treating time lasting,cell apoptosis and death increase.Therefore,the clinical application of AgNPs must be careful,expecially the concentration and treating time.Objective The aim of this work was to assess the effect of AgNPs on mouse macrophage RAW 264.7,and to explore the influencing mechanism.Also we observed whether if AgNPs could activate the mouse macrophage RAW 264.7 and stimulate the inflammatory factors.Methods We observed the changes of mouse macrophage RAW 264.7 after treatment by AgNPs with inverted microscope.And the work evaluated the changes of cell viability,cell apotosisand cell cycle with treatment by AgNPs.And we assessed the inflammatory factors levels by qPCR.Results After different concentration(0?4?8?16?32?g/mL)of AgNPs treatment for 24h,the shape and size of RAW 264.7 did not change,but black particles increased in the cells along with the concentration of AgNPs increasing.The cell viability did not change much,and cell cycle and apoptosis test were similar to the control.Along with the increasing concentration of AgNPs,mRNA level of IL 6 increased,which meaned that AgNPs could stimulate and activate the macrophages.Conclusion In this study AgNPs within 32?g/mL could not change the cell viability,cell apotosis and cell cycle,but could stimulate and activate the secretion of the macrophage.The mRNA level of IL-6 and TNF-? increased.AgNPs could activate the immune system,which help to clean the infection in apical periodontitis.