Maintaining oral health for a hundred years and more? - An analysis of microbial and salivary factors in a cohort of centenarians

Abstract

Aim: To investigate associations between oral health-related conditions and the oral microbiome in a representative study sample of centenarians.

Materials and methods: Clinical and microbial parameters from 54 centenarians were assessed in the Heidelberg Dental Centenarian Study. Plaque and salivary samples were collected, and the microbiota was characterized by 16S rRNA gene sequencing.

Results: Diversity and structure of the oral microbiome were mainly influenced by the presence of natural teeth and the number of decayed, missing, and filled teeth (0.028 ≤ p ≤ 0.001 in plaque and salivary samples). Centenarians with less caries experience possessed a more diverse oral microbiome. Moreover, the number of dental visits also showed a significant influence on the microbial composition. Most centenarians presented with hyposalivation (mean stimulated flow rate = 0.84 ± 0.55 ml/min), a low buffering capacity, and an acidic pH. The latter was between 5.0 and 5.8 in 46.3% of cases, and we observed that an increased salivary pH correlated with higher alpha-diversity in both salivary and plaque samples.

Conclusion: The microbiome diversity correlated significantly with successful oral aging. In addition, regular dental visits were a beneficial factor. However, diversity can be negatively influenced by hyposalivation, associated with pH changes due to aging effects.

Keywords: Oral microbiome; centenarian; dental caries; epidemiology; saliva; tooth loss.

Figure 1.

Microbial composition in salivary and in plaque samples, in order of increasing DMFT (only the 25 most abundant genera are represented).

Figure 2.

PCoA analysis of microbiota in dentate and edentulous centenarians with different DMFT.

Figure 3.

Microbial diversity in successful oral ages (≥ 20 remaining teeth) and others, in (a) salivary and in (b) plaque samples. Impact of the type of denture on the microbial diversity in (c) salivary and in (d) plaque samples.

Figure 4.

Differential abundance of taxa between edentulous and dentate patients. The differential analysis was performed with Deseq2 at the level of amplicon variants, genus and phylum. Taxa over-represented in one group are color-coded (green: dentate, red: edentulous). (a) Cladograms showing the differentially abundant taxa between edentulous and dentate patients in salivary and plaque samples. Overlapping shading is due to significant differences in the genus or phylum, in cases where a genus is more abundant in the dentate group but the whole phylum is more abundant in the edentulous group. (b) Relative abundance and log2 (fold change) of the differentially abundant taxa between edentulous and dentate patients. The differential analysis is shown at the level of amplicon variants (top part), genus (middle part) and phylum (bottom part).

Figure 5.

Influence of the salivary pH on the microbial diversity in (a) salivary and in (b) plaque samples.