| In our research, we investigated the constituents and contents of amino acids in dental plaque fluid and their association with caries susceptibility in children and teenagers, also observed the different contents in various amino acids with baseline. Along with two other factors of saccharose and fluoride, the change of amino acids contents was observed, which would help to discover the association between amino acid and caries susceptibility.Researches on epidermiology and animal experiments testify that sugars take part in the progression of caries and they are the main cariogenic material. Sugars promote the progress of caries in this way: 1.Glycolysis generates acid, and the organic acids accumulate on the surface of enamel causing teeth demineralization and they participate in the progress of caries. This is the most important pathogenesis.2.To synthesize insoluble extracellular polysaccharide and take part in the formation of dental plague matrix, which provide preparation for the bacteria adhesion. 3.To synthesize intracellular polysaccharide and soluble extracellular polysaccharide, so as to maintain the continuity of sugar use of bacteria and store the energy . 4.To provide ATP for bacterial metabolism.Many researches have testified that fluoride can decrease the risk of caries with complicated mechanism,now we discuss the effect of fluoride on oral bacteria.1.Fluoride's effect on bacteria growth. 2.Fluoride's effect on carbohydrate metabolism of bacteria. Fluoride can suppress the activity of glycolytic enzymes and the bacterial absorption of glucose, and decrease the acid generation.3.Fluoride can effect the compound of bacterial macromolecule.In our research,3~5-year-old children 42 and 15~20 -year-old teenagers 36 were divided into caries free group(CF) and caries susceptible group(CS), based on the degree of caries : DMFS≥10 with active caries(chalky enamel and decayed below dental plaque on the cervical zone)in CS ,and DMFS=0 in CF.All volunteers can not accept any dental care 24hs before test(including tooth brushing and using dental floss).Nobody can eat anything 2hs before sampling. The samples are gathered for 3 times from supragingival dental plaque on all teeth except mandibular anterior teeth. After excluded with cotton rolls, the dental plaques were dried with air syringe and collected, then samples were carried to the lab 2hs after dental plaque was put in 1.5ml centrifugal tubes lyophilized by ice.After centrifuged(4℃, 15000g, 45min), about 2-5μl dental plaque fluid was left from every sample, which were stored in refrigerator of -20℃. Each sample was diluted into 30μl with KH2PO4(pH =7.0),added NaHCO3 (pH=7.030μ)and10μl DNFB ,then they were bathed for an hour in water of 60℃, after that they were diluted into 0.25ml with KH2PO4 (pH=7.0),then analysed the amino acids in dental plaque fluid with high performance liquid chromatogralphy.Among the 17 amino acids determined, the glutamate content was the highest and it is very important in the metabolism of dental plaque.The amidogen of glutamate could absorb and store nitrogen,provide the materials of aminos for the growth and metablism of bacteria. Moreover the glutamate is the core factor of transamination in dental plaque.Amino acids metabolism in dental plaque fluid and the products are related to the progress of caries, among which arginine and proline might suppress caries. The content of arginine in dental plaque was low but play an important role in maintaining neuter gender of dental plaque.The generation of ammonia through arginine pathway can raise the pH in dental plaque. The arginine pathway is widely exist in S.Mutant and B.Mutant.The ammonia generated both from arginine and urea are two important factors in maintaining the environment stability of dental plaque. Arginine has been reported by Kleinberg to be the main substrate for decarboxylation by oral microbes and substrate production of putrescine, which contributes to an accelerated rise in plaque pH.Arginine raised th...
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