Culture-based studies have shown that Streptococcus mutans and lactobacilli are associated with root caries (RC). The purpose of the present study was to assess the bacterial diversity of RC in elderly patients by use of culture-independent molecular techniques and to determine the associations of specific bacterial species or bacterial communities with healthy and carious roots. Plaque was collected from root surfaces of 10 control subjects with no RC and from 11 subjects with RC. The bacterial 16S rRNA genes from extracted DNA were PCR amplified, cloned, and sequenced to determine species identity. From a total of 3,544 clones, 245 predominant species or phylotypes were observed, representing eight bacterial phyla. The majority (54%) of the species detected have not yet been cultivated. Species of Selenomonas and Veillonella were common in all samples. The healthy microbiota included Fusobacterium nucleatum subsp. polymorphum, Leptotrichia spp., Selenomonas noxia, Streptococcus cristatus, and Kingella oralis. Lactobacilli were absent, S. mutans was present in one, and Actinomyces spp. were present in 50% of the controls. In contrast, the microbiota of the RC subjects was dominated by Actinomyces spp., lactobacilli, S. mutans, Enterococcus faecalis, Selenomonas sp. clone CS002, Atopobium and Olsenella spp., Prevotella multisaccharivorax, Pseudoramibacter alactolyticus, and Propionibacterium sp. strain FMA5. The bacterial profiles of RC showed considerable subject-to-subject variation, indicating that the microbial communities are more complex than previously presumed. The data suggest that putative etiological agents of RC include not only S. mutans, lactobacilli, and Actinomyces but also species of Atopobium, Olsenella, Pseudoramibacter, Propionibacterium, and Selenomonas.

Purpose-The present study used a new 16S rRNA-based microarray with probes for over 300 bacterial species better define the bacterial profiles of healthy root surfaces and root caries (RC) in the elderly.Materials-Supragingival plaque was collected from 20 healthy subjects (Controls) and from healthy and carious roots and carious dentin from 21 RC subjects (Patients).Results-Collectively, 179 bacterial species and species groups were detected. A higher bacterial diversity was observed in the Controls as compared to Patients. Lactobacillus casei/paracasei/ rhamnosus and Pseudoramibacter alactolyticus were notably associated with most root caries samples. Streptococcus mutans was detected more frequently in the infected dentin than in the other samples, but the difference was not significant. Actinomyces were found more frequently in Controls.Conclusion-Actinomyces and S. mutans may play a limited role as pathogens of RC. The results from this study were in agreement with those of our previous study based on 16S rRNA gene sequencing with 72% of the species being detected with both methods.

The purpose of the present study was to describe the bacterial diversity in the oral cavity of the elderly without root caries using bacterial microarrays, and to determine the site-and subject-specificity of bacterial colonization. Samples were collected from the tongue dorsum, mucosa of the buccal fold, hard palate, supragingival plaque from sound root surfaces, and subgingival plaque from the same roots. A new 16S rRNA gene based microarray method was used for the simultaneous detection of approximately 300 bacterial species. Overall, 175 species and clusters were detected, representing 8 phyla. Species belonging to the genera Streptococcus, Veillonella and Fusobacterium were common in all sites. The number of species per subject varied from 51 to 81. Statistical analyses revealed about 40 species or clusters with significant associations with at least one of the sites. The bacterial diversity was highest in the cheek and palate regions. Species typically associated with caries and periodontitis were detected rarely or not at all. The oral bacterial flora of the elderly appears to be diverse, and to a large extent site-rather than subject-specific.

All the nine species analysed were found to be present in initial carious root lesions as well as sound root surfaces but in different quantities, independent of the different periodontal therapies.

Parotid function tends to change upon aging, with possible consequences as to caries activity. However, analyses of individual samples revealed considerable variations in protein patterns.

This review gives an overview of the bacterial diversity of cultivated and not-yet-cultivated bacterial species in oral biofilms. Examples are given from the healthy oral cavity of youngsters, adults, and the elderly; caries in primary and permanent teeth; root caries in the elderly; subgingival plaque; aggressive periodontitis; chronic periodontitis; necrotizing ulcerative periodontitis; halitosis; noma; endodontic infections; and spreading odontogenic infections. Transfer of biofilm bacteria to the blood is also discussed. Techniques used for identifying these organisms are mainly PCR, cloning, and 16S rRNA gene sequencing, as well as microarrays. As much as 50% or more of the microbiota in oral biofilms cannot yet be cultured. This may have significant implications for our knowledge of the pathogens in major biofilm infections in the oral cavity such as caries, periodontitis, peri-implantitis, and mucositis. Furthermore, several bacterial species not traditionally believed to be oral pathogens have also been shown to be associated with disease.

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