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.  

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