| Caries is one of the most prevalent diseases in the world.In addition to causing huge economic losses,it also poses a serious threat to people's quality of life.However,traditional caries treatment has not achieved good results.In recent years,the idea of using probiotics to prevent and treat dental caries has attracted a lot of attention.This method has high safety and strong feasibility,and the patient suffers from the pain in the treatment and the economic loss is small,which is a very ideal treatment for caries.However,the relevant research is short-lived,the results are lacking,and the types of anti-caries probiotics are very limited.And the mechanism of action for its efficacy is not clear.In this study,13 strains of lactic acid bacteria deposited in the laboratory were tested for their antibacterial activity,and the main pathogen of dental caries,Streptococcus mutans,was used as indicator bacteria to screen the lactic acid strain with antibacterial activity as a preparation for anti-caries probiotics.And then evaluate the potential hazard of selected strains;explore the mechanism of the bacteriostatic action of the selected strains through the fluorescence staining technology,laser confocal technology(CLSM)and scanning electron microscopy(SEM).Finally,based on the previous research on the treatment of dental caries with active natural products,curcumin was selected and compounded with selected strains to explore the effect of prevention and treatment on dental caries under the the combined conditions.The results showed that 5 of the 13 strains of lactic acid bacteria had inhibitory effects on S.mutans,which were YRL45 and YRLP45,QL-2,Q7 and T1,respectively.After eliminating the action of acid and H2O2,they can still form a 10-11 mm inhibition zone,and it is initially determined that the antibacterial effect is a protein product.Risk assessment showed that 5 strains of lactic acid bacteria have lower application risks.Their fermentation end point p H is above 3.80,and the fermentation end point p H of the T1 strain is as high as 4.17,which is higher than the known anti-carious probiotics,Streptococcus salivarius.The corrosiveness to dentin is also significantly lower than that of S.mutans,and it is different from the corrosive effect of S.mutans on the teeth.The corrosiveness of the five strains of lactic acid bacteria on the teeth reached the h ighest at 1 h and then stopped.Simmiquently,they produce between 14-15% mg/m L of sugar during fermentation,with the ability to colonize and survive independently in the mouth.The mechanism by which lactic acid bacteria inhibit S.mutans is by inhibiting the formation of S.mutans biofilm.Their fermentation and supernatants(FNS)interfere with the normal formation of biofilms from the amount of biofilm,structure,survival of intracellular biofilm,and extracellular polysaccharides(EPS)in the biofilm.The formation of biofilm in the presence of FNS decreased by 5.45-30.91%,and the formation of biofilm structure order,the survival of bacteria in the membrane and the amount of EPS can be observed under the microscope.In addition,in the compounding experiment of probiotics and curcumin,the culture solution containing the live bacteria and curcumin exhibited a synergistic effect on the inhibition of S.mutans.YRL45,YRLP45,QL-2,Q7 and T1 five strains of lactic acid bacteria have an inhibitory effect on S.mutans,and have a certain safety in clinical application.The mechanism of its antibacterial action is preliminarily determined,which is consistent with the anti-carious probiotics.Application conditions can be used as a candidate strain for anti-caries probiotics.The results of this study enriched the strain library of anti-caries probiotics,preliminarily clarified the mechanism of antibacterial,and explored the synergistic antibacterial effect of probiotics with natural active products.It provides a theoretical basis for the development of anti-caries probiotics. |
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