The oral microbiome can predict childhood caries

Early childhood caries is an oral disease common in young children.  The infection leads to sustained demineralization of tooth enamel and dentin and can also spread to gums and surrounding areas.  Unfortunately, the damage from this disease is irreversible and can put a child at risk for tooth loss for the rest of his or her life.  In an effort to explore different ways to prevent childhood caries, researchers from China sought to investigate whether or not changes in the oral microbiomes of children could serve as a predictive measurement for development of caries.  

In a longitudinal cross sectional study conducted over 2 years, the researchers examined spatial and temporal variations in the microbiomes of 50 4-year old preschoolers.  The researchers took microbiota samples from saliva and plaque at four different time points.  Based on clinical monitoring among this cohort, the children were further segmented into 3 groups based on diagnosis: 1) healthy, which constituted 17 children, 2) caries onset, which constituted 21 children, or 3) caries progression, which represented 12 in the group. 

It was found that the caries onset group experienced delayed microbiota development, adjusted for age (which has shown to be a significant confounder as microbiota composition changes significantly during development).  Furthermore, changes in microbiota composition were more associated with ECC in onset children as opposed to progression, thus lending to the possibility of using the microbiome composition as a predictive tool.  In this light, the researchers developed a model termed Microbial Indicators of Caries (MiC) and successfully diagnosed ECC saliva/plaque samples from healthy samples with 70% accuracy, while predicting ECC onset in children with 80% accuracy.  The MiC model derived a readout based on an identified “intermediate” state of microbiota that represents a compositional shift. 

We’ve discussed in the past how microbiome composition and metabolites could be indicators of disease.  These findings point to another potential tool that can use features of the microbiome as a diagnostic method.  More research and further understanding of our microbiome can introduce a new field with the potential to provide immense health benefits.  

Saliva regulates our oral microbiome

We know that saliva is important during eating and digestion, but researchers from Harvard and MIT investigated how saliva may be influencing the microbiome.  In an article recently published in Applied and Environmental Microbiology the scientists describe results that show saliva also includes molecules that influence oral bacteria so as to prevent cavities.

Cavities are formed when bacterial biofilms form on teeth and produce acids that go on to dissolve tooth enamel.  Saliva, which flows through the mouth, works to wash away these bacteria and helps remineralize teeth.  Beyond this, it contains molecules called mucins, which are a component of body mucous that are known to influence the microbiome and which have been associated with many autoimmune disaeases.    Before now, it was unknown how salivary mucins impacted the oral microbiome.

Researchers combined the bacteria Streptococcus mutans, which is known to be one of the many bacterial culprits behind cavities, with salivary mucins in the presence of artificial teeth.  They discovered that while the mucins did not prevent the bacteria from growing and proliferating, they did in fact prevent the S. mutans from attaching to the artificial teeth.  In fact over 95% of biofilm formation (which can cause cavities) was decreased between control samples and samples with the mucins.  The scientists noted that in the samples with mucins the cells simply never formed biofilms, and stayed in the planktonic (i.e. free floating) form.  They speculate that the mucins either physically prevent binding or are somehow changing the genetics of S. mutans so as to prevent production of binding proteins.

Follow-up studies in human subjects that compare the presence of mucins with cavity abundance would be interesting to see.  We all know people who, despite brushing and flossing multiple times a day, still seem to get cavities (myself included!), and others who, despite not going to a dentist in years and never brushing, don’t get any cavities at all.  Perhaps the concentration of mucins is responsible, and perhaps we could add mucins to toothpaste and forget about cavities all together.  

Mouth diseases and tooth loss may be caused by oral microbiome alterations

Chronic periodontitis is a prevalent inflammatory disease of the tissue around and supporting the teeth and is the leading cause of tooth loss in the United States. Scientists at the University of Florida recently published a study in Applied and Environmental Microbiology that studied the oral microbiome of 25 healthy individuals and 25 individuals with chronic periodontitis, in order to determine if there are any consistent microbial differences between the groups.

In the study, they found that patients with periodontal disease had an altered oral microbiome with microbial communitites that were more homogeneous than healthy individuals’.  They were able to identify two specific groups of bacteria, Fusobacterium and Porphyromonas, that were associated with periodontitis and another two groups of bacteria, Rothia and Streptococcus, that were prevalent in the majority of the healthy sites without periodontitis.  The scientists also identified several genes that were involved with various biological activities that were enriched in the oral microbiome of healthy individuals.

This study provides more insight into the possible microbial causes of chronic periodontitis, which is common among adults in the United States. While this study is limited because of its small sample size and its lack of diversity among severity of chronic periodontitis disease, it is still a great starting point for further inquiry into the disease. The scientists also compared their work to previous studies utilizing Human Microbiome Project (HMP) participants, though the HMP only included healthy individuals and excluded individuals with periodontal disease.  Further research could lead to the discovery of better ways to both treat and prevent the disease by altering the microbial communities of our mouth.