Saliva protects teeth against cavities more than we thought

Date: Nov-12-2014 Mucus - part of the 0.5% of saliva that is not water - contains

salivary mucins, compounds that actively protect teeth from damage by

the cavity-causing bacterium Streptococcus mutans, according to

a new study.

The new study suggests salivary mucins play an active role in keeping our oral microbiomes healthy.

Previously it was thought that salivary mucins - large glycoproteins

- did little more than keep mucus in saliva slippery and elastic,

contributing to its gel-like properties. But now it seems they play an

active role in defending against pathogens and keeping the human

microbiome healthy.

First author Erica Shapiro Frenkel, of Harvard University, and

principal investigator Katharina Ribbeck, a professor at the

Massachusetts Institute of Technology, both in Cambridge, MA, report

their findings in the journal Applied and Environmental

Microbiology.

Frenkel says their findings suggest boosting the body's natural

defences might be a better way to prevent tooth decay than relying on

external agents like sealants and fluoride treatments.

The researchers found that salivary mucins do not alter levels of

S. mutans nor kill the bacteria over 24 hours. Instead, they

keep the bacteria suspended in a liquid medium, and this in turn

reduces their ability to form biofilms on teeth.

"This is particularly significant for S. mutans," Frenkel

explains, "because it only causes cavities when it is attached, or in a

biofilm on the tooth's surface."

A biofilm is a densely packed community of microbes that grow on

surfaces and surround themselves with sticky polymers that they

secrete.

Frenkel also points out that the oral microbiome - the collection of

friendly bacteria in the mouth - is better preserved when naturally

present species are not killed. "The ideal situation," she adds, "is to

simply attenuate bacterial virulence."

Salivary mucins prevent tooth decay bacteria from forming a biofilm

S. mutans causes tooth decay by first attaching itself to

teeth by forming a biofilm from sticky polymers that it produces. As

the bacterium grows under the protection of the biofilm, organic acid

byproducts of its metabolism attack the tooth enamel, causing

cavities.

For their study, the researchers focused on how the salivary mucin

MUC5B affects the ability of S.mutans to attach to teeth and

form a biofilm. These are the two key steps necessary for cavities to

form, Frenkel explains.

The investigation grew out of previous work looking at gastric

mucins in pigs that protected against lung pathogens. The researchers

wondered if salivary mucins might also play a protective role.

Frenkel says common diseases like cystic fibrosis, ulcerative

colitis and asthma have been linked to problems with mucin

production.

"There is increasing evidence that mucins aren't just part of the

mucus for structure or physical protection, but that they play an

active role in protecting the host from pathogens and maintaining a

healthy microbial environment," she adds.

Prof. Ribbeck says this kind of research is important because it

changes scientists' views on host-microbe interactions:

"It is generating a paradigm shift from the textbook view of mucus

as a simple catchall filter for particles, towards the understanding

that mucus is a sophisticated bioactive material with powerful

abilities to manipulate microbial behavior."

Meanwhile, Medical News Today recently learned that Roman Britons had less gum disease than

modern Britons. The surprising discovery provides further evidence

that modern habits like smoking can be damaging to oral health.

Written by Catharine Paddock PhD

Not to be reproduced without permission.

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Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.