Caries and the Oral Microbiome

Dental caries in young children remains a problem world-wide with profound and life-long systemic implications.  In particular, severe-early childhood caries (ECC) can devastate the dentition of young children, impact general health and a child’s self-esteem because of poor appearance.  The infection can spread from primary to permanent teeth extending effects beyond childhood.  An association between childhood obesity and dental caries is an additional complication of dental caries.

The major caries risk factors are dietary fermentable carbohydrates and infection with acidogenic bacteria that demineralize teeth.  The etiology of dental caries has focused on acidogenic and acid-tolerant Streptococcus mutans and Lactobacillus species.  The microbiome of carious lesions, however, is very complex.  We included non-selective blood, and selective acidic, anaerobic culture to examine severe-ECC.  Strain identification used partial 16S rRNA sequence comparisons with the Human Oral Microbiome Database (www.HOMD.org).  Sequence based analysis of the 16S rRNA libraries indicated >90% population coverage with greater diversity in blood than in acid isolates.  This diversity was comparable to that observed using molecular methods. 198 HOMD taxa were identified, including 45 previously uncultivated taxa, 45 potential novel groups, and taxa without cultivated representatives.  S. mutans, Bifidobacteriaceae and a new acidogenic and acid-tolerant species, Scardovia wiggsiae, were strongly associated with severe-ECC.  In adolescents with orthodontic appliances, we detected S. wiggsiae associated with early carious lesions, indicating that S. wiggsiae could be involved in caries pathogenesis in initial and late-stage lesions.

Multivariate modeling including species detected using HOMIM (mim.forsyth.org) revealed heterogeneity within severe-ECC with the impact of diet and infection differing between children.  Multi-species changes were observed in children with disease resolution but not in children with caries progression, or by only monitoring S. mutans.  Monitoring the complex oral microbiome expands our understanding of the caries-associated microbiota and can provide tools to improve clinical outcomes.  

Dental caries is a plaque-associated infection, as is gingivitis and periodontitis.   Detection of gingival/periodontal species in young children indicated the microbiota of these infections is frequently acquired early in life.  Thus, complete understanding of the dental and systemic complications of the oral microbiome should include studies involving children.