| Objective: The aim of this study was to estimate the count of Streptococcus mutans in children's saliva by Real-time PCR to evaluate the effect of a new fluoride varnish on the Streptococcus mutans count in saliva of these children,and investigate the duration of the anticaries effect in microecological perspective.Methods: Twenty-six school-age children were divided into caries group(dmfs?1)of thirdteen and caries-free group(dmfs=0)of thirdteen according to the results of oral examination.Baseline saliva samples were collected from all the subjects before the application of the fluoride varnish(Duraphat?).Subsequent saliva samples were collected at the end of the1 th hour,the 1th week,the 2th week,the 3th week,the 4th week,the 8th week and the 12 th week after the varnish application.The genomic DNA of Gram-positive bacteria in saliva and the genomic DNA of Streptococcus mutans were extracted by genomic DNA kit(centrifugal column method).The number of Streptococcus mutans at each time node was detected by real-time quantitative PCR(absolute quantification).The number ofStreptococcus mutans was indicated by median.The difference between the two groups was analyzed by Mann-Whitney U test in before and after the varnish application.The difference was statistically significant by P<0.05,and its changing trend was analyzed.Results: There was statistically difference in the quantity of Streptococcus mutans in caries group and caries-free group before the varnish application(P <0.05).The quantity of Streptococcus mutans in caries group showed an obvious downward trend,and the differences were statistically significant at the 8th and the 12 th week(P<0.05);however,there was no significant change in caries-free group(P>0.05).Conclusion: Duraphat? can significantly reduce the quantity of Streptococcus mutans in saliva of caries-active children,and have a long term effect.So it may be an effective caries-preventive measure for caries-susceptible children. |
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