| Periodontal diseases and Dental caries are common lesions within the human mouth , They have all taken the plaque as the initiation factor. Within this total, the bacteria caused an important factor in dental caries and periodontal disease. However, because the pathogenic bacteria, pathogenesis and clinical features are quite different, People used to regard the two as independent diseases and are often researched separately. With the development of in-depth study of biofilm and oral microbiology, it has revealed further the importance of the bacteria interaction in the development of dental caries and periodontal infection. But the relationship between the two diseases has not been clearly explained. Clinically, we often find in people susceptible to periodontal disease, the tooth are relatively healthy, and the people who are underlying the risk of dental caries ,the periodontal health conditions were relatively good, and the clinical studies have confirmed this point. Meanwhile, Carlssonproves Streptococcus mutans produce antagonistic hydrogen peroxide material with the same mechanism of periodontal pathogens Streptococcus sanguis. Thereby, inspired us to thinking, we consider whether there is antagonism and inhibition between periodontal pathogens and cariogenic bacteria in vitro environment. This study is an extension of clinical trials, Porphyromonas gingivalis and Streptococcus mutans are investigate object. Through Sabine methods in vitro we explore the rise and fall of relations between the two bacteria, in order to deepen understand of the etiology of dental caries and periodontal disease.Specific experiment methods are as follows: [1] Recovery of international standards bacterium. Purchase the Porphyromonas gingivalis (Pg ATCC 33277) and Streptococcus mutans (GS-5) strains from the Capital University of Medical Sciences, Institute of Stomatology. Streptococcus mutans choose MSagar. Porphyromonas gingivalis use tryptone-soybean (TS) as the medium , in the medium 5% calf serum and 1% of blood chloride Red--vitamin K1 for species recovery.[2] Preparation of bacterial suspensions. Proliferation and purification the bacteria after the recovery, purifiedspecies were inoculated in a liquid medium, anaerobic training, 3000r/min centrifugal 20min, collecting bacteria, and adding saline to make the necessary concentration of bacterial suspension. [3] Smash the Streptococcus mutans and the supernatant of cultured bacteria collected .①The liquid of Ms cultured bacteria was centrifugal 20min in 3000r/min, collecting cell, and adding PBS buffer for sonicating, 60W ultrasonic power, 3min, 0.45μm filter, disposable precipitation, the supernatant collected for standby.②The collection of bacterial culture supernatant after centrifugation, pack it tube back for standby. [4] Sabine method antibacterial experimental group.①Preparation of Pg viable dish. Draw 20μl of the Pg suspension, drop in the TS agar plate surface. Coating uniformity with sterile glass push rod, make the dish with Pg viable. Then punch four equidistant holes with a 5mm diameter hole-puncher, remove the agar in the holes with a sterile toothpick. adding melting Ms medium in the holes (about half deepth of the holes) and waiting for solidification.②Test group. Group 1 : Adding 50μl Ms viable suspension in one hole of each dish; Group 2 : Adding 50μl crushed Ms liquid in one hole of each dish; Group3 :Adding 50μl the liquid of Ms culture supernatants in one hole of each dish; Control group : Adding partes aequales Ms liquid medium on one hole in each dish.③Place each group dish in anaerobic tank, Palladium catalyst for tablets, anaerobic incubation at 37℃for 48 hours to observe the inhibition zone size.Experimental results showed:①In the first group, the experimental group(containing Ms strains)formed an clearly visible range of inhibition zone around the hole without instructions bacteria, but in the control group, the Pg grow very well around the holes, having no inhibition zone. Statistics show that the inhibition zone diameter decreases with the increasing concentration of Pg, which shows that the antimicrobial of the Ms are negative correlated with the Pg′concentrations. It proves that the whole Ms continuously secreted and metabolic some material that inhibits the growth of Pg.②In the second and third group, the experimental group(Ms culture supernatant fluid filtration or crushed) has no inhibition zone around the holes similar to the first group, and the antibacterial activity is not detectable. There is no difference between the experiment group and the contorl group. This shows that the inhibition substance doesnot exist in Ms culture supernatant fluid filtration or crushed.③Based on the experimental results of the study and Ms can produce the nature of hydrogen peroxide, we can infer that the inhibition of Ms to the growth of Pg maybe relative with the hydrogen peroxide secreting by MS,but unrelated with Ms′intracellular material and mutacin. The conclusion: [1] Streptococcus mutans has an action of inhibition on Porphyromonas gingivalis . [2] Streptococcus mutans bacteria smash filtration fluid and the supernatant fluid of Streptococcus mutans has no inhibition on Porphyromonas gingivalis. [3] The Streptococcus mutans can produce antibacterial substance , this substance was primarily found in the bacterial cells, live bacteria cells continuously produce such antimicrobial substances during metabolism to act on the other bacteria.There are still some problems to be solved : Although we confirmed in experiments on the suspension of Streptococcus mutans inhibiting the growth of the Porphyromonas gingivalis. However, the mechanism of the Streptococcus mutans'inhibitive function and what material that the Ms metabolism produces inhibits the growth of Porphyromonas gingivalis is still uncertain. Therefore, we willcontinue to study these in the follow-up research. In addition, how about dynamic "Transfer" of the two pathogenic bacteria in the micro-environment of dental plaque is not clear, and we will continue to explore this area In the future research. Study on the relationship between periodontal disease and dental caries are still in "the initial stage." In future studies we should combine advanced molecular biology techniques and effective microbial technology, and further study of the relationship between the two diseases plaque. The clinical significance of this experiment is certain: The dental caries and periodontal diseases are two common human dental diseases, the incidence rate has been relatively high, although not life-threatening, but these two diseases are genetic, and the final results are all the missing of the teeth, and can affect the appearance and function ,and have an impact on the development of young people ,seriously sick would have triggered a psychological disorder. With the progress of medical science and technology, biomedical model has changed to the bio-psycho-social model .There is an urgent need for us to make early prevention, diagnosis and treatment. We do this step today, "related bacteria", dental caries andperiodontal disease is to further study the relationship of these two diseases, in order to provide scientific basis for the two diseases, deepening the understanding of the cause of dental caries and periodontal disease. It can also work as a guide for better disease prevention and early treatment of periodontal treatment– we should take strict measures against dental caries, and also should pay attention to the respective periodontal treatment during dental restoration treatment.
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