RESUMO
AIMS: To quantitatively identify Bifidobacterium, S. wiggsiae and S. mutans in plaque samples obtained from children with severe-ECC and caries-free groups and to analyze their association with caries-related factors retrieved from the questionnaire in each group. STUDY DESIGN: To establish the 2 study groups, clinical examination in 122 Thai children, aged 2-5 years, recorded decayed, missing and filled teeth scores (dmft), in addition to plaque and gingival indices. Sixty one children in the caries-free group and 61 in the S-ECC group were identified. A questionnaire was used to assess the parent's attitudes and behavior regarding the child's oral hygiene care and diet. METHODS: Pooled overnight supra gingival plaque was collected from each child using a sterile toothpick, released in 1 ml of TE buffer, transported on ice to the Laboratory and stored at - 20 °C. DNA was extracted from the plaque based on enzymatic lysis and quantitative real-time PCR using fluorescent dye (SYBR green) in addition to Agarose gel electrophoresis were performed. All laboratory and retrieved from the questionnaire data per child were recorded and statistically analysed. RESULTS: S. wiggsiae (p < 0.005) and S. mutans (p < 0.001) were higher in the S-ECC group. Bifidobacterium, S. mutans, and S. wiggsiae were associated with the dmft score and gingival index (p < 0.001). The dmft scores of children who detected only S. mutans were significantly lower than the dmft scores of children who detected two bacteria; S. mutans + S. wiggsiae (p = 0.028), S. mutans + Bifidobacterium (p = 0.026), and three bacteria; S. mutans + Bifidobacterium + S. wiggsiae (p = 0.007). Children who found all three bacteria (Bi + Sm + Sw) had the highest dmft scores, followed by children who had two bacteria (Bi + Sw, or Bi + Sm, or Sw + Sm). The guardians' education levels, occupations, household income, prolonged bottle feeding, taking of water after bottle or breast feeding, eating sugar-coated crackers or bread with sweetened cream, and premature birth were the factors that related to S-ECC. CONCLUSION: Levels of S. wiggsiae and S. mutans, guardian's education, family economics, prolonged bottle feeding, eating high sugar-containing snacks and premature birth were associated with S-ECC.