Molecular Microbiological Analysis of Severe Caries in Young Permanent Teeth

Dental caries is the most common chronic disease of childhood, and is the biggest unmet health care need among America's children. We do not have a complete understanding of the complex microbial etiology of childhood caries. Dental plaque contains several hundred different organisms, many of which are poorly studied. In addition, comparatively little attention has been paid to identifying health-associated bacterial species. Objectives: Our purpose was to identify bacterial species present in health and established severe caries of the young permanent dentition using an open-ended molecular approach. Methods: Plaque samples were collected from 21 subjects with severe caries, age 9 to 17, and 18 healthy controls matched by age, race, and sex. A plaque sample was taken from each of four sites in each caries subject: intact enamel, whitespot lesions, the surface of cavitated lesions, and deep dentin. Quantitative clonal analysis of bacterial 16S ribosomal genes isolated from the plaque samples was used to identify species present in established severe caries and in health. Data was analyzed using SAS PROC MIXED. Results: Overall there were 7 Lactobacillus species that were significantly associated with caries, several of which were found at high levels. Other significant caries-related species included Streptococcus mutans, Bifidobacterium inopinatum, and Propionibacterium oral clone (FMA5). Species that were found at high levels, and were associated with health included Streptococcus mitis/oralis/pneumoniae, Streptococcus sanguinis, Streptococcus gordonii, Veillonella spp., Corynebacterium matruchotii, Selenomonas noxia and Gemella haemolysans/morbillorum. Multiple additional species found at lower levels were significantly more common in health than in caries. Conclusions: Streptococcus mutans was the dominant species in the earliest stage of caries in the majority of cases, and as caries progressed, Lactobacillus species showed a larger increase and were the dominant genus. In addition, several health-related species appear to be lost as caries progresses. Supported by NIH DE16125.