Caries status and quantification of four bacteria in saliva of Chinese preschool children: A cross-sectional study

Background/purposeMutans streptococci, bifidobacteria, and lactobacilli are acidogenic and aciduric bacteria which may be associated with early childhood caries (ECC). This study aimed to analyze the bacterial composition of four cariogenic microorganisms, namely Streptococcus mutans, Streptococcus sobrinus, Bifidobacterium spp., and Lactobacillus spp. in the saliva of Chinese preschool children and to assess the association of the bacterial burden with the caries status.Materials and methodsA total of 109 saliva samples were collected from 36 children with ECC and 73 caries-free (CF) children aged 2–4 years. A questionnaire was used to evaluate other caries risk factors such as dietary habits and oral hygiene practice. A quantitative real-time polymerase chain reaction was performed to determine the presence and loads of the four microorganisms. Pearson's correlation test was conducted to evaluate the relationship between the World Health Organization caries diagnostic criteria dmft/dmfs index scores and saliva levels of the selected bacteria.ResultsThe prevalence of S. mutans and S. sobrinus in children with ECC was 88.9% and 19.4%, respectively, whereas the prevalence in CF children was 76.7% and 4.1%, respectively. The saliva levels of S. mutans and S. sobrinus in children with ECC were significantly higher than in CF children (P = 0.004 and P = 0.007, respectively) and positively correlated with dmft/dmfs index scores (r = 0.321/0.316 and r = 0.271/0.245, respectively). An association was found between children with caries-active lesions and the frequency of sugar consumption (P = 0.004). No significant difference in the presence and load of Bifidobacterium spp. or Lactobacillus spp. were found between the two groups.ConclusionS. mutans, S. sobrinus, and sugar consumption appear to be associated with caries status in the studied population, which might be useful for caries screening in Chinese preschool children.