Abstract
Dental caries is an endogenous microbial-community-based disease resulting from an ecological shift from dynamic stability to metabolic imbalance in a consortium of acidogenic and aciduric bacteria comprising the dental plaque biofilm. Participants were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal investigation of health and behaviour in a cohort born in Dunedin, New Zealand. Oral biofilm samples (collected at age 32) from anterior labial supragingival, posterior lingual supragingival, posterior subgingival and the dorsum of the tongue habitats for 841 participants were analysed using checkerboard DNA-DNA hybridisation (CKB), focussing on 30 ecologically significant bacteria. Associations of CKB data with dental caries at ages 32 and 45 years were assessed using regression modelling, adjusting for potential confounders including sex, xerostomia and oral hygiene. The putative periodontitis pathobiont Tannerella forsythia (in the anterior supragingival biofilm) was associated with untreated caries at age 32. The percentage of total summed cell number counts (%TPC) for two putative periodontitis-associated species (T. forsythia and Micromonas micros) were associated with greater caries experience at age 32 and the development of new caries between age 32 and 45. Additionally, severe caries (3+ cavities) was associated with putative caries pathobionts (Lactobacillus fermentum, Lactobacillus plantarum), periodontitis-associated species and commensals (M. micros, Campylobacter rectus, Streptococcus mitis biovar I, Streptococcus mitis biovar II) in the subgingival biofilm. Participants with sustained poor oral hygiene through to age 32 not only had greater experience of caries by that age than those with good oral hygiene (fully-adjusted IRR = 5.10, 95% CI 3.30, 7.89) but also experienced greater incidence of new caries from age 32 to 45 years (IRR=3.69, 95% CI 2.62, 5.20). These findings provide evidence in support for the extended caries ecological plaque hypotheses, the polymicrobial aetiology of caries, and the integrated aetiology of dental caries and periodontal diseases. They also underscore the roles of poor oral self-care (particularly over the life-course) and xerostomia in the occurrence and progression of caries.