Cavities Infectious

Cavities. Getty

That cavity you got a filling for was likely thanks to some bacteria. These bacteria make a home in our mouths. They can eat away bits of our teeth if we're not careful.

There are ways to avoid having these bacteria eat away at our teeth. It's about more than just avoiding sweets - though those candies the bacteria may munch away on and then multiply with.

Cavities Can Be Contagious

Our mouths are filled with bacteria.

  Some of these bacteria cause cavities. Some bacteria appear to protect us against cavities.

The bacteria associated with cavities can break down the sugars we eat. These bacteria can break down sugars. These are sugars like glucose, fructose, and sucrose that are broken into lactic acid. This acid production can make plaque, the sticky coating on our teeth, acidic. This acidic plaque can break down and soften the tooth enamel. It demineralizes the enamel. This breakdown can then reach below the hard enamel and then into the dentin, which is softer and more easily damaged, and then into the pulp of the tooth. This is how bacteria can get within our teeth and how cavities (also called caries) and dental abscesses are formed.

The bacteria remain when we brush our teeth and rinse our mouths. Brushing though can keep our gums and teeth from being overrun with bacteria. This is especially because after meals and snacks can help rid our mouths of the food these bacteria break down.

Why a Dry Mouth Can Be a Problem

It’s not just brushing our teeth (and using fluoride containing water and rinses) that protects our teeth from these bacteria. Those with dry mouths will not be as protected; saliva cleans teeth and protects against acidity. Smokers may have drier mouths which can make them more prone to cavities.

Others with dry mouths include those who take some epileptic medications, antihistamines, or other medications, or have medical conditions (like Sjogren’s )that cause dry mouths. Overnight we have drier mouths so making sure we brush before going to bed is particularly important. Alcohol can also damage the enamel risking cavities.

It's not just bacteria. It Matters Which Bacteria Are There

This also means that what bacteria we have in our mouths matters. We don’t know what bacteria we have. We just have a lot of bacteria, often a lot of different varieties. We all have many types of bacteria in our mouths – just like on our skin or in our guts – throughout our lives. We can’t rid ourselves of these bacteria – as they would just be replaced by others.

What bacteria a child has in his or her mouth can be associated with having more cavities. Mom may pass on some of these bacteria to her kid. Some bacteria are associated with protection from cavities; other bacteria is associated with having more cavities.

In particular, Streptococcus mutans, Actinomyces, Lactobacillus are associated with cavities, while Streptococcus sanguinis, which is closely related, is associated with fewer cavities. These different bacteria may work together – or against each other – in creating cavities. It’s not usually just one type of bacteria working alone, but rather the effects of the whole population of bacteria which leads to cavities or not.

Usually what bacteria we have in our mouths doesn’t change much. What bacteria is in our mouths today will likely be there tomorrow and next week. However, if we are exposed to new bacteria, we can acquire new bacterial populations. Infants usually acquire most of their bacteria from their mothers or family. A mother sharing utensils and food can pass bacteria from her mouth to her child’s  – which may be good or bad for cavities. These bacteria can also be spread with a kiss. We can spread cavities, then, to our loved ones.

Given the role of bacteria in causing cavities, there has been work on finding ways to avoid these bacteria. There has been talk of developing a vaccine against bacteria associated with cavities. These vaccines have looked particularly at Strep mutans. There was even research into developing a chewing gum to help. This chewing gum that would contain a bacteria that would overcome the bacteria associated with cavities. Simply taking a short course of antibiotics however would not clear up the bacteria associated with cavities; bacteria would quickly return. Infections suspected to have led to dental abscesses or more severe infections however often need antibiotics.

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