A Tissue-Dependent Hypothesis of Dental Caries

Abstract

Current understanding of dental caries considers this disease a demineralization of the tooth tissues due to the acid produced by sugar-fermenting microorganisms. Thus, caries is considered a diet- and pH-dependent process. We present here the first metagenomic analysis of the bacterial communities present at different stages of caries development, with the aim of determining whether the bacterial composition and biochemical profile are specific to the tissue affected. The data show that microbial composition at the initial, enamel-affecting stage of caries is significantly different from that found at subsequent stages, as well as from dental plaque of sound tooth surfaces. Although the relative proportion of Streptococcus mutans increased from 0.12% in dental plaque to 0.72% in enamel caries, Streptococcus mitis and Streptococcus sanguinis were the dominant streptococci in these lesions. The functional profile of caries-associated bacterial communities indicates that genes involved in acid stress tolerance and dietary sugar fermentation are overrepresented only at the initial stage (enamel caries), whereas other genes coding for osmotic stress tolerance as well as collagenases and other proteases enabling dentin degradation are significantly overrepresented in dentin cavities. The results support a scenario in which pH and diet are determinants of the disease during the degradation of enamel, but in dentin caries lesions not only acidogenic but also proteolytic bacteria are involved. We propose that caries disease is a process of varying etiology, in which acid-producing bacteria are the vehicle to penetrate enamel and allow dentin degrading microorganisms to expand the cavity.

Functional profiles of coronal and dentin caries in children

“…This contrasted with the genes of dentin caries, which differed from each other and reflected a wider range of metabolic capabilities. Differences in the microbiome composition from enamel (coronal) to dentin caries and increased diversity in dentin caries was observed in a metagenomic analysis [13] as in the current report. The pH of dentin caries was found to vary considerably ranging from pH 4.5 to over pH 7, with the different microbiotas being associated with various levels of acidity [28], consistent with the diversity in the microbiota in dentin caries sites observed of the current report.…”

“…Previous studies have shown differences in microbial gene expression based on sample site within the oral cavity [13] between health and periodontitis [14] and dental caries [15,16]. Microbial gene expression activity in dentin can differ markedly from that in enamel and closer to the tooth surface [16].…”

Molecular and Histological Association Between Candida albicans from Oral Soft Tissue and Carious Dentine of HIV-Positive Children

“…It was not attempted to determine whether oral bacteria co-existed with C. albicans or that they possibly facilitated the penetration of the organism deep into the dentine, but from previous in vitro studies it would be feasible that it can be the case [40]. No claims are made based on the results of this study regarding the cariogenic potential of C. albicans.…”

Cariogenic microflora and pH in superficial and deep layers of occlusal carious lesions - A metagenomic analysis

“…[14] Recent molecular study using second-generation sequencing and metagenomic techniques has discovered an extraordinary ecosystem where S. mutans accounted for only 0.7-1.6% of carious lesions. [10,33] However, some recent studies indicate that the relationship between S. mutans, and caries is not absolute high proportions of S. mutans may persist on tooth surfaces without lesion development, and caries can develop in the complete absence of S. mutans. [34,35] Veillonella are an acidogenic Firmicutes with 5.8% of the total population.…”