Quantitative analysis of biofilm bacteria according to different stages of early childhood caries

•We compared data obtained by qPCR in dental biofilm of ECC- children in different stages of the disease.•L. acidophilus and L. casei group were rarely identified in dental plaque samples.•S. mutans and Bifidobacterium spp. were more abundant in biofilm of children with dentinal lesions. Monitoring selected key species related to health or disease may facilitate caries risk assessment and discovery of novel ecological preventive and therapeutic approaches. This study aimed at quantifying Actinomyces naeslundii, Bifidobacterium spp., Lactobacillus acidophilus, Lactobacillus casei group, Streptococcus gordonii, Mitis group and Streptococcus mutans by quantitative polymerase chain reaction (qPCR) in dental biofilm from Brazilian children with different stages of early childhood caries (ECC). Seventy-five preschool children were clinically evaluated by ICDAS criteria and divided into groups: caries-free (CF; n = 20), enamel caries lesions (ECL; n = 17) and dentine caries lesions (DCL; n = 38). Plaque samples from all children were collected for detection and quantification of the selected bacteria. L. acidophilus and L. casei group were absent in almost all plaque samples. No differences in relative proportions of A. naeslundii, Mitis group and S. gordonii were observed in any stage of caries. However, S. mutans and Bifidobacterium spp. were present at higher concentrations in the biofilm of children with DCL (p