Aims: To quantify Streptococcus mutans, lactobacillus and bifidobacterium in initial and mature plaque collected from children with severe early childhood caries (S-ECC) and caries-free (CF) groups and to analyse the association between these bacteria and caries-related factors in each group.
Study design: A collection of 120 initial and overnight supra-gingival plaques were collected from Thai children aged 2-5 years-old (S-ECC = 60, CF = 60). Plaque, gingival indices and decayed, missing, filled tooth (dmft) scores were recorded. A questionnaire was used to assess the parents' attitudes and behaviour regarding the child's oral hygiene care and diet.
Methods: After DNA extraction, quantitative real-time polymerase chain reaction (PCR) using fluorescent dye (SYBR green) was performed.
Results: Levels of Streptococcus mutans, lactobacillus and bifidobacterium in both initial and mature plaques of S-ECC were significantly higher than those from the caries-free group (p < 0.05). The ratio of S. mutans, lactobacillus, and bifidobacterium to the total bacteria in S-ECC was significantly higher than in the caries-free group (p < 0.05). Levels of lactobacillus and bifidobacterium in both plaques significantly correlated with dmft scores and the plaque index, while S. mutans levels only correlated with dmft scores (p < 0.05). Factors that were significantly associated with caries were parents's education, duration of bottle feeding, especially during sleeping and the frequency of consuming cariogenic food between meals (p < 0.05).
Conclusion: Levels of S. mutans, lactobacillus, bifidobacterium and the ratio of these bacteria to total bacteria in both initial and mature plaques were significantly higher in children with S-ECC and related to dmft scores, oral hygiene and dietary habits.
Keywords: Bifidobacterium; Dental plaque; Early childhood caries; Lactobacillus; Polymerase chain reaction; S. mutans.