16 May 2023

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Microbial indicators of dental health, dysbiosis and early childhood caries

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Dental caries lesions are a clinical manifestation of disease, preceded by microbial dysbiosis, which is poorly characterized and thought to be associated with saccharolytic taxa. Here, researchers assessed the associations between the oral microbiome of children and various caries risk factors such as demographics and behavioral and clinical data across early childhood and characterized over time the salivary and dental plaque microbiome of children before clinical diagnosis of caries lesions.

The oral microbiome establishes, matures, and changes throughout life in response to various physiological and environmental factors. To ensure that the oral ecosystem remains healthy, it needs to adapt to changes occurring in the oral environment. When the natural equilibrium between the host and its oral microbiome shifts toward an imbalanced, also called dysbiotic, state, this can promote demineralization of a tooth surface and increase risk of dental caries. A dysbiotic shift in the oral microbiome toward a cariogenic state commences before the manifestation of a caries lesion and is, therefore, challenging to determine and characterize.

The study was part of a larger project, “Predicting Caries Risk in Underserved Toddlers in Primary Healthcare Settings.” The current study is a longitudinal prospective cohort observational study. No intervention was performed during the study.

Children (N = 266) were examined clinically at ~1, 2.5, 4, and 6.5 y of age. The microbiome samples were collected at 1, 2.5, and 4 y.

Caries groups consisted of children who remained caries free (International Caries Detection and Assessment System [ICDAS] = 0) at all time points (CFAT) (n = 50); children diagnosed with caries (ICDAS ≥ 1) at 6.5 y (C6.5), 4 y (C4), or 2.5 y of age (C2.5); and children with early caries or advanced caries lesions at specific time points.

Microbial community analyses were performed on zero-radius operational taxonomic units (zOTUs) obtained from V4 of 16S ribosomal RNA gene amplicon sequences.

The oral microbiome of the children was affected by various factors, including antibiotic use, demographics, and dietary habits of the children and their caregivers. At all time points, various risk factors explained more of the variation in the dental plaque microbiome than in saliva.

At 1 y, composition of saliva of the C4 group differed from that of the CFAT group, while at 2.5 y, this difference was observed only in plaque. At 4 y, multiple salivary and plaque zOTUs of genera Prevotella and Leptotrichia were significantly higher in samples of the C6.5 group than those of the CFAT group.

In conclusion, up to 3 y prior to clinical caries detection, the oral microbial communities were already in a state of dysbiosis that was dominated by proteolytic taxa. Plaque discriminated dysbiotic oral ecosystems from healthy ones better than saliva.

Kahharova D, Pappalardo VY, Buijs MJ, et al. "Microbial Indicators of Dental Health, Dysbiosis, and Early Childhood Caries." Journal of Dental Research. 2023;0(0). doi:10.1177/00220345231160756