DNA Sequence Analysis Of Cariogenic Bacteria Of School-age Children With Caries In Shijiazhuang

Objective:Dental caries is one of the common and major diseases endangering human teeth health in oral cavity.Dental caries is a progressive and destructive teeth disease with hard tissue demineralization and organic elements decomposition chief under the action of bacteria and multiple factors.Dental caries and caries mechanism became a research hotspot in the fields of stomatology.Children are the caries susceptible population.Streptococcus mutans has been confirmed as the main caries bacteria.However,it is not clear whether cariogenic ability of Streptococcus mutans infected children exists difference,bacterial mutation and how much threat to children teeth is.Whether there is the relationship between the living habits and dental caries of children? It is rare report on gene mutation and cariogenic ability of Streptococcus mutans infected children.The oral health of children determines the long-term development strategy of oral health in a country.Study on dental caries of children is the key point in the stomatological researches.Streptococcus mutans causes dental caries via generates dental plaque on the teeth surface and produce acid which destroyed teeth directly.So,the study on the mechanism of cariogenic bacteria is mainly focused on the analysis of bacterial stain,colony morphology,biochemical characteristics,metabolites and the influence of plaque bio-film.The analysis of mutation rates at the molecular level is rare.This study focused on the analysis of nucleic acid sequence(DNA sequence)and the muntation rate of cariogenic bacteria in order to probe the role of Streptococcus mutans muntation results in children's caries.The children caries investigations of Shijiazhuang(Foreign Languages Primary school,Primary School affiliated Teacher-training University,Shilipu Primary School,Fangbei Primary School),were performed from July 2015 to February 2016.The children accepted sealant were aged 8~12 years old in Hospital of Stomatology,Hebei Medical University.Specific primers were designed for Streptococcus mutans,extraction of dental caries was performed from dental plaque of school-age children for PCR amplification.PCR positive cases were carried out nucleic acid sequencing to confirm the mutation rate of different genotypes of Streptococcus mutans.The relationship between the gene mutation and cariogenic ability of Streptococcus mutans in children was discussed.Methods:1 According to WHO Oral Health Standard,60 children were selected from Shijiazhuang(Foreign Languages Primary school,Primary School affiliated Teacher-training University,Shilipu Primary School,Fangbei Primary School).The children accepted sealant aged from 8~12years old were enrolled in Hospital of Stomatology,Hebei Medical University during July 2015 to February 2016.Sixty respondents were divided into caries-disease group and caries-free group and 30 children in each.2 Clinical data of caries incidence were collected by questionnaire to analyze the relationship between children's habits of bedtime snacks,brushing and dental caries.3 The plaques on the buccal and lingual enamel of 60 school-age children were collected.4 PCR was used to identify the main caries bacteria in school-age children.5 Nucleic acid sequencing was used to determine the genotype,mutation rate of the main caries bacteria,and the difference of caries-disease group and caries-free group of bacteria mutation rate.6 Nucleic acid sequencing results were used to construct phylogenetic tree of Streptococcus mutans to determine the evolutionary distance between Streptococcus mutans.7 Rank Sum Tests and Chi-square were used to analyze statistically the gene mutation rate and positive detection rate of Streptococcus mutans.Results:1 The phenomenon of children's bedtime drinks and desserts was prevalent in 60 school-age children.There was no significant difference in bedtime drinks and dessert of school-age children.2 The results showed that the school-age children had developed the habit of brushing teeth.Caries-disease children were more than caries-free children in the evening brushing.3 The results of PCR confirmed that 31 children infected Streptococcus mutans,in which caries-disease group contained 21 cases and caries-free group contained 10 cases.There was a significant difference in the detection rate of Streptococcus mutans in caries-disease group and caries-free group(P<0.05).4 The results of DNA sequence analysis showed that Streptococcus mutans mutation rate of caries-disease group was 12.7% ~ 31.3%,with an average of 21.314%.Streptococcus mutans mutation rate of caries-free group was 32.3% to 39.2%,with an average of 36.14%.There was significance difference in the mutation rate of caries-disease group and caries-free group(P<0.05).The mutation rate of Streptococcus mutans of caries-free group was much higher than that of caries-disease group.5 The system of phylogenetic tree confirmed that the Streptococcus mutans strains of caries-disease group were more close to the standard Streptococcus mutans than that of caries-free group.Conclusion:1 Streptococcus mutans was the main pathogen of school-age children's caries.2 Streptococcus mutans which infected children exists much gene mutation.Streptococcus mutans mutation rate of children with caries-disease was 12.7%~31.3%,with caries-free was 32.3% ~ 39.2%(P< 0.05).3 When the mutation rate of Streptococcus mutans achieved or achieved above 36.14%,the cariogenic ability of Streptococcus mutans decreased significantly(P<0.05).