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The Oral Microbiome: Good vs. Bad Bacteria in Your Mouth

The oral microbiome

How to promote a healthy oral microbiome.

Mouths are amazing, complex places filled with life: more than 500 million oral bacteria might call a single tooth home. If it’s been more than a few hours since you brushed your teeth, there may be more microbes living in your mouth than there are people on earth.

Some of these oral bacteria can cause cavities, gingivitis and bad breath. But they’re not all bad. Much of the bacteria in your mouth are actually good for you and are on your side, defending your teeth and gums, freshening your breath, and aiding in the digestive process.

Scientists have identified more than 700 different species of oral bacteria that live in the mouth and make up your oral microbiome. Believe it or not, your unique combination of microbes might even be as identifying as a fingerprint. The bacteria in your mouth’s microbiome live together, work together, and affect your health together. When it comes to oral health, promoting the growth of good bacteria may be even more important than eliminating bad bacteria. Researchers are just beginning to decode the complex balance of oral bacteria—and what it means for you.


Some bacteria help digest food and protect against harmful microbes in the food you eat. The details are still being studied, but it is known that these bacteria in your mouth work as a team. Some helpful microbes produce substances that make it easier for their neighbors to grow and thrive.


Don’t forget: many of the bacteria in your mouth don’t have your best interests in mind. Take Streptococcus mutans, for example: S mutans feasts on sugar and pumps out tooth-dissolving acid compounds. These acids dissolve the outer layer of tooth enamel and lead to tooth decay.

If you find yourself with a case of bad breath, you might have Porphyromonas gingivalis, Treponema denticola, or Prevotella intermedia to thank. These gassy little creatures make cozy homes in the crevices between your teeth and just below your gumline.

These “bad” bacteria team up and work together just like their friendlier counterparts. Some strains pre-digest substances found in the food you eat so it can be more readily absorbed by their odor-emitting neighbors.

Using an antiseptic mouthwash such as LISTERINE® Cool Mint can help kill up to 99.9% of these “bad” bacteria that can cause bad breath, plaque and gingivitis that can have a negative impact on your oral health.


The overall mix of microbes in your oral microbiome is more important than any single species. You may not be able to give your mouth an instant germ makeover, but there are a few simple actions you can take to help the bacteria help you.

Number 01

Avoid sugar

When you eat, you aren’t just feeding yourself, you’re feeding the bacteria that live in your body. The tooth decay-causing bacteria in your mouth LOVE sugar—the more you eat, the more enamel-dissolving acid they spit out.

Number 2

Oral hygiene

A top-notch oral care routine includes brushing and rinsing with mouthwash twice per day and cleaning between your teeth daily. The bacteria in your mouth are constantly producing gingivitis disease causing plaque, so regularly removing it with a thorough brushing is crucial.

Number 3

Visit your dentist

An oral exam will help your dentist see if your mix of microbes is out of whack. A professional cleaning will remove buildup you can’t remove yourself and if necessary, they can recommend ways to sharpen up your oral hygiene regimen.