Molecular Studies of the Structural Ecology of Natural Occlusal Caries

Abstract

Microbiological studies of occlusal dental biofilms have hitherto been hampered by inaccessibility to the sampling site and demolition of the original biofilm architecture. This study shows for the first time the spatial distribution of bacterial taxa in vivo at various stages of occlusal caries, applying a molecular methodology involving preparation of embedded hard dental tissue slices for fluorescence in situ hybridization (FISH) and confocal microscopy. Eleven freshly extracted teeth were classified according to their occlusal caries status. The teeth were fixed, embedded, sectioned and decalcified before FISH was performed using oligonucleotide probes for selected abundant species/genera associated with occlusal caries including Streptococcus, Actinomyces, Veillonella, Fusobacterium, Lactobacillus and Bifidobacterium. The sites showed distinct differences in the bacterial composition between different ecological niches in occlusal caries. Biofilm observed along the entrance of fissures showed an inner layer of microorganisms organized in palisades often identified as Actinomyces, covered by a more loosely structured bacterial layer consisting of diverse genera, similar to supragingival biofilm. Biofilm within the fissure proper seemed less metabolically active, as judged by low fluorescence signal intensity and presence of material of non-bacterial origin. Bacterial invasion (often Lactobacillus and Bifidobacterium spp.) into the dentinal tubules was seen only at advanced stages of caries with manifest cavity formation. It is concluded that the molecular methodology represents a valuable supplement to previous methods for the study of microbial ecology in caries by allowing analysis of the structural composition of the undisturbed biofilm in caries lesions in vivo.

Analysis of Bacterial Activity in Sound and Cariogenic Biofilm: A Pilot in vivo Study

“…Considering that the role of at least three of them in the caries process has also been confirmed in other studies [Beighton, 2005;Tanner et al, 2011;Torlakovic et al, 2012;Dige et al, 2014], we considered Streptococcus mutans , lactobacilli, Bifidobacterium dentium , and Scardovia wiggsiae as representatives of caries-associated bacteria. In contrast to the former taxa, it was shown that asaccharolytic fusobacteria are more associated with healthy teeth than with caries lesions, but they can be found in all stages of caries [Wolff et al, 2013].…”

“…In contrast, Bifidobacteriaceae were found to be more involved in established caries lesions than in early stages, expressing their activity in further acidification of the final pH [van Houte et al, 1996;Dige et al, 2014]. Furthermore, B. dentium was found to grow slowly under low pH conditions but is highly resistant to low pH [Nakajo et al, 2010].…”

Ecological Hypothesis of Dentin and Root Caries

“…In contrast to root surfaces, coronal dentin will only become colonized by bacteria after total breakdown of the enamel [Dige et al, 2014]. Dentin caries lesions possess highly diverse microbiotas Obata et al, 2014;Schulze-Schweifing et al, 2014;Simón-Soro et al, 2014], which can lead to the development of strictly anaerobic conditions [Edwardsson, 1974;Hoshino, 1985].…”

Predicting Dental Caries Outcomes in Children

“…Although most of this initial evidence remains to be validated, plausible genetic associations may influence tooth anatomy and quality, salivary factors, taste preference, immunity, the oral microbiome, and other factors. The genome, along with the oral microbiome (metagenome), and their interactions (transcriptome, proteome, and metabolome) at the tooth surface level (Nyvad et al 2013;Dige et al 2014) remain largely unappreciated in caries risk assessment and personalized clinical decision making.…”