A Preliminary Study Of Amoxicillin For Intracanal Antisepsis Of Enterococcus Faecalis Infection

Background and Objective:Enterococcus faecalis is the most common bacteria in refractory periapical periodontitis.The treatment of refractory periapical periodontitis is one of the challenges in Endodontics.It is difficult to eradicate Enterococcus faecalis and its biofilm with existing intracanal antisepsis drugs,which is one of the basic reasons of persistent infection of refractory periapical periodontitis.Amoxicillin is one of the preferred drugs for systemic use of antibiotics in Endodontics.In many cases,amoxicillin has obvious effect on refractory periapical periodontitis with obvious exudation.However,local application of antibiotics in root canal is a more effective way of administration.Therefore,this study explored the appropriate dosage and mode of amoxicillin for intracanal medication of Enterococcus faecalis infection,and laid a theoretical foundation for clinical application of amoxicillin in intracanal antisepsis.Methods:1.Antibacterial effect of amoxicillin solution on suspended Enterococcus faecalis:The minimal inhibitory concentration of Amoxicillin against Enterococcus faecalis was determined based on microdilution.The measured values were compared with the guide data to standardize the concentration of the standard solution.The minimum bactericidal concentration of amoxicillin against Enterococcus faecalis was determined based on minimal inhibitory concentration.2.In vitro study on the effect of amoxicillin solution on the activity of Enterococcus faecalis biofilm: Taking the minimal inhibitory concentration of amoxicillin on Enterococcus faecalis as reference,the inhibition of amoxicillin solution of different concentrations on biofilm activity of Enterococcus faecalis was studied by spread plate method,and the appropriate dosage of amoxicillin for intracanal antisepsis was preliminarily screened.3.In vitro study on Amoxicillin was used to intracanal medication of Enterococcus faecalis infected roots : Based on the selected dosage,amoxicillin was sealed into the simulated Enterococcus faecalis infected root canal model of in the form of gel,paste or cotton dipping solution,and compared with calcium hydroxide.The results of scanning electron microscope and live/dead bacteria staining were used to observe Enterococcus faecalis and its biofilm in root canal wall and dentine tubules.To explore the appropriate administration of amoxicillin for intracanal medication of Enterococcus faecalis infection.Results:1.The antibacterial effect of amoxicillin solution on suspended Enterococcus faecalis: The minimum inhibitory concentration of amoxicillin against Enterococcus faecalis is 0.5μg/m L,and the minimum bactericidal concentration is 0.6μg/m L.2.In vitro study on the effect of amoxicillin solution on the activity of Enterococcus faecalis biofilm: Amoxicillin solution had obvious and stable inhibitory effect on the biofilm proliferation of Enterococcus faecalis in the concentration range of 0.25-32μg/m L.3.In vitro study on Amoxicillin was used to intracanal medication of Enterococcus faecalis infected roots: the results of scanning electron microscope and live / dead bacteria staining showed that when amoxicillin-sodium carboxymethyl cellulose gel with antibiotic concentration of 1 μ g/m L was used for intracanal medication of Enterococcus faecalis,the amoxicillin gel had a uniform and strong killing effect on the biofilm of bacteria of the root canals wall,and had a significant effect on bacteria in dentine tubules.When the amoxicillin paste group and the cotton twist extract with 1μg/m L concentration were used as intracanal medication,it also had obvious killing effect on the bacterial biofilm of the root canals wall,however,the mixed distribution of live and dead bacteria is obvious,and the living dead bacteria were also scattered in the dentinal tubule,which was considered to be caused by the drug can not contact with the root canals wall evenly.Residues of drugs or related substances were seen in various forms of administration in the experiment.Conclusion:1.Amoxicillin can be used as a good antibacterial agent to introduce intracanal antisepsis for Enterococcus faecalis infection.2.1 μ g/m L can be used as one of the reference dosages of the effective concentration of amoxicillin as intracanal medication of Enterococcus faecalis infection.3.The synthesis of amoxicillin gel with sodium carboxymethyl cellulose as thickener can be used as one of the reference administration methods of amoxicillin as intracanal medication of refractory periapical periodontitis.