Dental caries and mutans streptococci in relation to plasma ascorbic acid

Ascorbic acid (AA) affects in vitro growth of bacteria and may also act in vivo to decrease caries activity. The aim of this study was to evaluate the possible association of AA level in plasma with number of caries lesions, relative numbers of some species of oral cariogenic flora, and rate of salivary secretion. The caries status and some bacteriologic variables of dentulous adult subjects with a low level of AA in the plasma (≤25 μmol/1; n =75) were compared with those of controls (plasma level ≥50 μmol/1; n =75) matched for age, sex, and number of teeth. For each subject, site-specific recordings of the presence or absence of plaque, dental caries, fillings, and erosions were recorded clinically by the same dentist in a double-blind system. The amounts of visible plaque and numbers of decayed tooth surfaces were significantly higher in the low AA group than in the controls. No between-group differences were found in the number of fillings and the amount of oral bacterial growth. The frequencies of consumption of vegetables, berries, and other fruit were significantly lower in the low AA group than in the controls.     

Catheter Ablation of AV Conduction Using Radiofreguency Current in Atrial Tachy－arrhythmias

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肺炎杆菌的耐药机理研究

对３４株肺炎杆菌氨基糖甙类抗生素耐药株进行接合转移试验，其中３１株的抗性可全部或部分转移给大肠杆菌，转移率为９１％，转移频率为１０＾－＾４－１０＾－＾６。肺炎杆菌在接合转移过程中其所携带的抗性基因可以部分解离。细菌的耐药性不同宿主细胞中的表达程度亦有不同。对６３株肺炎杆菌进行质粒谱分析。结果提示８５和５８ｋｂ的大分子量质粒是携带耐药因子的质粒，１３ｋｂ或其他小质粒与肺炎杆菌耐药性无关。尽管上述细菌     

Inverse correlation between the proportion of salivary bacteria inhibiting Streptococcus mutans and the percentage of untreated carious teeth

To evaluate the role of inhibitory substances produced by bacteria in the oral cavity, we estimated, by a deferred test on Todd-Hewitt agar enriched with hemin and vitamin K, the proportion of bacteria that inhibited or stimulated the growth of Streptococcus mutans and Porphyromonas gingivalis , from the saliva of 109 patients (54 males and 55 females) attending our dental clinics. The patients, aged from 8 to 75 years old (mean: 31±18 years), were randomly selected whatever the reason for their visit. The results, evaluated with the Spearman rank test, indicated that there was no statistically significant ( P >0.05) correlation between the proportion of salivary bacteria inhibiting or stimulating P. gingivalis with the Community Periodontal Index of Treatment Needs (CPITN), the number of carious, missing and filled teeth, or with the decayed, missing and filled teeth index (DMFT). Also, no statistically significant correlation was observed between the proportion of salivary bacteria stimulating the growth of S. mutans and the above mentioned health indexes. However, a statistically significant ( P <0.005) negative correlation was found between the percentage of cultivated bacteria that inhibit S. mutans and the percentage of untreated carious teeth as well as with the CPITN. The results thus indicate a possible role for inhibitory substances produced by bacteria in the maintenance of oral health.     

Systematic analysis of gingival s-tate and salivary variables as predictors of caries from 5 to 7 years of age

Abstract – The aim was to assess the caries predictive ability of gingival state, salivary counts of lactobacilli and S. mutans , salivary secretion rate and buffer capacity of the saliva from the ages of 5 to 7 yr. The material comprised 105 children who were examined once a year. All available screening levels were systematically tested for the single variables as well as for combinations of two or three variables. The screening levels were set where the highest possible sensitivity and specificity were reached simultaneously. The predictive values for positive and negative tests were then calculated. The S. mutans count turned out to have the best combination of sensitivity (0.41) and specificity (0.83). The single variables gingival state and S. mutans had constant screening levels, while the values for lactobacilli and buffer capacity varied. The saliva secretion rate could not be measured at 5 yr of age. Systematic analyses of predictive ability of combinations of two or three variables were then performed and did not result in any clinically significant improvements of the predictive ability. The observed low predictive ability might be explained by the fact that 1) many children changed their habits during the period of investigation and 2) they were examined and treated once a year according to their individual needs, which meant variations in conservative as well as in preventive treatment.     

Polysaccharide production by cell free transferases in saliva in relation to salivary microflora

Abstract – The supernatant of centrifuged whole saliva was incubated with radiolabeled sucrose to measure polysaccharide production by cell free transferases and to examine whether water-insoluble polysaccharides were produced. Amounts of polysaccharides were considered to reflect the level of cell free transferases in saliva. Plating samples on blood agar, MS and MSB plates gave salivary counts of total CFU, total streptococci, S. salivarius and S. mutans. The capability of the cell free portion of saliva to produce polymers was confirmed and it appeared that the cell free transferases were able to produce water-insoluble polysaccharides. Significant correlations were found between the total and the insoluble polysaccharides from ¹⁴C-G’-sucrose and total CFU, total streptococci, S. salivarius and S. mutans, respectively. Heavily S. mutans infected subjects seemed to produce particularly large amounts of water-insoluble polysaccharides from ¹⁴C-G’-sucrose. The apparently water-insoluble ¹⁴C-F’-polysaccharides correlated significantly to the number of S. salivarius. It was thus concluded that the constitution of the oral microflora and particularly the levels of S. mutans and S. salivarius were of importance for the level of cell free transferase activity.     

Salivary parameters and efficiency of dietary instructions to reduce sugar intake among 7–8-year-old schoolchildren

Abstract — The efficiency of dietary instructions was tested in a group of 7–8-yr-old schoolchildren. The instructions were given in the presence of the child's mother either verbally (control group n = 14) or both verbally and written (test group n = 12). For this purpose the salivary status of the first grade pupils ( n = 79) of a primary school in Turku was screened. Salivary flow, buffer capacity, sucrase activity, lactobacillus, yeast and S. mutans counts were determined. Children whose salivary lactobacillus count was over 10⁴ CFU/ml ( n = 32) were selected for the present study. The efficiency of the dietary instructions was measured as a reduction of salivary lactobacilli. There were no differences in the number of children with reduced LB counts or in the caries increment of 1 yr between the test and the control groups. However, children who succeeded in reducing the number of salivary lactobacilli (42%) within 4 wk revealed a significantly ( P <0.05) lower caries increment after 1 yr than the rest of the subjects. We concluded that children whose lactobacillus counts were reduced by the dietary instructions developed significantly less caries than children whose lactobacillus counts remained high after the instruction. No additional effect on lactobacillus counts and caries increment could be demonstrated by supplementing the verbal dietary counseling with written instructions.     

Prevalence of Streptococcus mutans with different colonial morphologies in human plaque and saliva

Abstract – Plaque and saliva samples were obtained twice from 58 children at an interval of 1 year and examined for the prevalence of Streptococcus mutans on Mitis salivarius (MS) and Mitis salivarius bacitracin (MSB) agar. Two types of S. mutans colonies with different colonial morphologies were seen on both media. They were serologically identified as serotypes c/e/f and d/g respectively. The first type, morphogroup c/e/f, had the typical "frosted-glass" appearance. It was the most prevalent and was found in 97% of the children. The second type, morphogroup d/g, had a creamy marzipan consistency with a dull, granular surface, gray to brown in color and often with some liquid around or on top of the colony. Group d/g was detected in 21 children (36%) and then together with colonies of group c/e/f. Children infected with single or multiple morphogroups of S. mutans generally harbored the same groups 1 year later. There was a significant positive correlation between the proportion of S. mutans in plaque and their numbers in saliva.