pH gradient and distribution of streptococci, lactobacilli, prevotellae, and fusobacteria in carious dentine

Abstract

Objectives Caries process comprises acidogenic and aciduric bacteria that are responsible for lowering the pH and subsequent destruction of hydroxyapatite matrix in enamel and dentine. The aim of this study was to identify the correlation between the pH gradient of a carious lesion and proportion and distribution of four bacterial genera; lactobacilli, streptococci, prevotellae, and fusobacteria with regard to total load of bacteria. Materials and methods A total of 25 teeth with extensive dentinal caries were sampled in sequential layers. Using quantitative real-time PCR of 16S rRNA gene, we quantified the total load of bacteria as well as the proportion of the abovementioned genera following pH measurement of each sample with a fine microelectrode. Results We demonstrated the presence of a pH gradient across the lesion with a strong association between the quantity of lactobacilli and the lowest pH range (pH 4.5–5.0; p = 0.003). Streptococci had a tendency to occupy the most superficial aspect of the carious lesion but showed no correlation to any pH value. Prevotellae showed clear preference for the pH range 5.5–6.0 (p = 0.042). The total representation of these four genera did not reach more than one quarter of the total bacterial load in most carious samples. Conclusion We revealed differential colonization behavior of bacteria with respect to pH gradient and a lower than expected abundance of lactobacilli and streptococci in established carious lesions. The data indicate the numerical importance of relatively unexplored taxa within the lesion of dentinal caries. Clinical relevance The gradient nature of pH in the lesion as well as colonization difference of examined bacterial taxa with reference to pH provides a new insight in regard to conservative caries management.

Functional profiles of coronal and dentin caries in children

“…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.…”

“…ADS and urease have been associated with reduced caries activity based on ammonia production and raising the pH to counterbalance acidic conditions typical of active caries [43]. It seems likely these enzymes also involved in the higher pH found deep in in dentin compared to the tooth surface [28]. Linking ADS with S. sanguinis and urease with A. naeslundii in the microbial community is consistent with the metabolic properties of these species.…”

The Role of Bacterial Biofilms in Dental Caries and Periodontal and Peri-implant Diseases: A Historical Perspective

“…Less aggressive cariogenic microbiomes appear to include other acidogenic species, such as Streptococcus, Actinomyces , and other taxa in Actinobacteria (Belda-Ferre et al 2012; Eriksson et al 2018). Caries in dentin, including root caries, can be characterized by Lactobacillus, Bifidobacterium , and Scardovia species in addition to S. mutans (Mantzourani et al 2009; Kianoush et al 2014), suggesting rapid disease progression, although proteolytic species may be cariogenic in deep dentin. Shifts in predominant caries-associated microbiomes in different stages and sites of caries lesions are determined by environmental ecologic factors (Takahashi and Nyvad 2016; Fig.…”

The Oral Microbiome of Children: Development, Disease, and Implications Beyond Oral Health

“…For instance, healthy children (from 3 months old) already harbor potentially cariogenic bacteria ( S. mutans ), which increase in abundance with age [35, 52]. Additionally, among 3-month old children, Increased presence of Lactobacilli, a taxon that tends to dominate carious lesions [41, 53] may be predictive of caries at 3 years [34]. These observations suggest that a combination of extrinsic and intrinsic factors determine oral disease phenotypes later in childhood.…”