Oral flora: healthy oral flora and symptoms of disturbed flora

More than 800 different bacteria live in your mouth. This so-called biofilm (a layer of microorganisms surrounded by self-produced mucus attached to a surface) is important for the health of your teeth and protects against diseases and infections. If the composition of your oral flora is out of balance, that is, if pathogenic germs gain the upper hand, this can lead to tooth decay, gingivitis or even periodontal disease. The most obvious sign is bleeding gums and inflammation of the gums (gingivitis). Bad breath can also be a sign of an imbalance in oral flora, as well as a persistent bad taste in the mouth. Some bacteria not only cause inflammation, they also release sulfur compounds. This is how the unpleasant or foul odor comes about.

  • A mouth full of bacteria
  • What is oral flora?
  • Healthy oral flora
  • Delicate balance
  • Investigate oral flora
  • Types of bacteria in the mouth
  • Types of bacteria
  • Balance
  • Mouth flora develops
  • Good bacteria in the mouth
  • Dangerous bacteria in the mouth
  • Fighting bacteria in the mouth
  • Symptoms of a disturbed flora
  • Remedies against bacteria in the mouth
  • Yogurt or kefir
  • Chlorophyll
  • Sage, thyme and lemon
  • Tea tree oil
  • Baking soda
  • Black and green tea
  • Oil pulling
  • Marigold or calendula
  • Chamomile
  • Mouthwashes
  • Restore or improve oral flora
  • Probiotics
  • Xylitol
  • Hydrogen peroxide


A mouth full of bacteria

Even if you don’t see or feel anything, the oral cavity is full of life and activity. Millions of microorganisms are teeming in the mouth. Bacteria colonize not only the teeth, but also the tongue. It is estimated that approximately two-thirds of all oral bacteria colonize the posterior portion of the tongue. Bacteria and food remains (tongue coating) are present there. Some people have a lot of bacteria on their tongue if they do not remove the tongue plaque regularly. The result is bad breath. Bacteria also occur on the teeth, the oral mucosa, between the teeth, the pockets, in the gums and sometimes even in the root canal of the teeth. A tooth root infected and inflamed with bacteria causes severe toothache and many people have already experienced it. The biggest cause of tooth decay, the bacteria Streptococcus mutans, forms sticky deposits in the mouth called biofilm or plaque. A paradise for these bacteria in the oral cavity are hidden places that are difficult to reach with a toothbrush. Food residues accumulate there, which the caries bacteria metabolize. This creates aggressive acids that attack tooth enamel and over time cause tooth decay.

What is oral flora?

The oral flora is the set of microorganisms that live in the oral cavity. It varies from person to person: each individual has a very special composition of bacteria in the mouth. The oral flora mainly consists of hundreds of different types of bacteria. Some species are even only found in the oral flora, and therefore not in the intestine, the organ in which numerous microorganisms form the intestinal flora. In addition to bacteria, fungi (especially the yeast Candida albicans), viruses and other micro-organisms, such as small single-celled organisms, occur in the mouth.
Microbes of all kinds feel comfortable in the mouth because it is warm and moist there and they can find enough food. Bacteria in the mouth are transmissible. For example, when kissing, millions of microorganisms migrate from one mouth to the other. Usually beneficial and harmful microbes keep each other at bay. However, certain influences can cause the oral flora to become unbalanced. Then ‘bad’ bacteria multiply more intensely, giving them the upper hand.

Smoking is bad for the oral flora / Source: WerbeFabrik, Pixabay

Healthy oral flora

Delicate balance

Healthy oral flora has an important protective function. The microorganisms in the mouth keep out harmful environmental influences, fend off dangerous germs and help digest food. Good oral flora ensures that teeth and gums remain healthy. However, some factors can disrupt the delicate balance of microorganisms in the mouth, such as:

  • poor oral hygiene
  • wrong, very sugary diet
  • tension and (chronic) stress
  • smoking
  • heavy alcohol consumption
  • poor condition of the teeth
  • age
  • weakened immune system
  • use of medication, such as antibiotics
  • diseases such as diabetes or cancer

Then the balance shifts in favor of some pathogens that endanger oral health. There is a risk of bad breath, tooth decay, gum disease (gingivitis ) or periodontitis, an inflammation of the supporting tissues of the teeth.

Investigate oral flora

A dentist can test the number and composition of bacteria in the mouth to see how your oral flora is doing. He determines which bacteria settle in the oral cavity and saliva by placing a cotton swab in your mouth and then sending it to a lab. In the laboratory, the microbes are multiplied and carefully analyzed under the microscope.

Candida infection in the mouth / Source: Adam J/Shutterstock.com

A saliva test also provides information about the yeast Candida albicans, a yeast that occurs naturally in and on the body and does not cause problems under normal circumstances. If the balance of the oral flora is disturbed, an infection with candida can occur.
Some particularly aggressive bacteria have been linked to the development of periodontal disease. A bacterial test shows which germs are exactly responsible for damage to the tooth-supporting structures. Microbiologists analyze the hereditary material (DNA) of the germs in the laboratory and identify the pathogen(s).

Types of bacteria in the mouth

The number of bacteria in the mouth is immense. Researchers estimate that billions of bacteria and approximately 800 different species can be found in the oral cavity; a hustle and bustle. Even in 2020, researchers are still discovering unknown subtypes of bacteria. These microorganisms can be roughly divided into ‘good’ and ‘bad’, the latter meaning ‘pathogenic’.

Types of bacteria

Some bacteria need oxygen for their metabolic processes (aerobic), while others can do without the gas from the air (anaerobic). Their ‘food’, for example, is protein and sugar from food scraps. Some microbes are permanent residents of the mouth, while others are only temporarily present in the oral cavity.


There is usually a balance between the microorganisms in the oral flora because they keep each other in balance. However, when the oral flora is disturbed, dangerous pathogens multiply, their numbers get out of control and cause problems in the mouth, gums and teeth.

Mouth flora develops

The oral flora must develop over time. A child in the womb does not yet have bacteria in its mouth. But microorganisms begin to colonize the oral cavity immediately after birth. Usually the first bacteria in the mouth are streptococci. Several other types of bacteria later appear as part of the oral flora, such as staphylococci or pneumococci.
The composition of the oral flora becomes increasingly complex over time , especially when the first teeth erupt. During puberty, the oral flora changes significantly again due to hormonal changes (similar to those during pregnancy). The gums receive more blood and are softer. Under these conditions, bacteria can more easily settle in the gums and cause gingivitis, for example.

Streptococcus salivarius / Source: CDC Richard R. Facklam, Ph.D., Wikimedia Commons (Public domain)

Good bacteria in the mouth

Most bacteria in the mouth are considered harmless and do not damage the teeth or gums. Some ‘good’ bacteria in the mouth also have a protective function. They act as a protective force and even promote oral and dental health.
An example is the beneficial bacterium Streptococcus salivarius, a gram-positive, facultative anaerobic bacterium. This bacterium has anti-inflammatory properties and displaces germs. The bacterium is one of the first to settle in the oral cavity. The bacterium Streptococcus sanguinis, a gram-positive, facultative anaerobic bacterium, also fights germs and prevents tooth decay. It colonizes the oral cavity when teeth begin to grow.

Dangerous bacteria in the mouth

In addition to the ‘good’ microbes, there are also dangerous bacteria in the mouth that promote tooth decay (cariogenic microorganisms) or gum disease:

  • Streptococcus mutans: This bacterium plays an important role in the development of tooth decay. Parents pass these bacteria on to their children when, for example, they kiss or lick the pacifier and then put it in the child’s mouth. Caries bacteria metabolize the sugar from food and produce acids, especially lactic acid. This attacks the tooth enamel and creates cavities in the teeth. Streptococcus mutans feels most comfortable in dental plaque.

Streptococcus mutans / Source: Y tambe, Wikimedia Commons (CC BY-SA-3.0)

  • Streptococcus mitis is part of the normal oral flora, but under certain conditions (e.g. increased sugar consumption) is associated with the development of tooth decay.
  • Lactic acid bacteria (lactobacilli) and fusobacteria promote tooth decay. The enzyme glucansucrase is produced from the lactic acid bacterium Lactobacillus reuteri and bacteria use the enzyme to convert sugar from food into long, sticky sugar chains. With the help of this adhesive, they adhere to tooth enamel.
  • Actinomycetes are ultra-small parasitic bacteria associated with gingivitis, cystic fibrosis and antimicrobial resistance.
  • Veillonella parvula is a normal part of the oral flora, but under certain conditions, such as a weakened immune system, it can cause diseases such as periodontitis and caries, as well as with various systemic infections.
  • The bacterium actinobacillus actinomycetemcomitans is particularly dangerous and responsible for a serious form of gingivitis. (periodontitis). The germs Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia and Treponema denticola also play an important role in periodontitis. In the course of periodontitis, the composition of the oral flora changes: atypical representatives may appear, for example, Escherichia coli bacteria in the mouth, which further aggravate periodontitis. However, they usually prefer to live in the intestines.

Rotting bacteria breakdown products cause bad breath.

Fighting bacteria in the mouth

If the oral flora is out of balance, dangerous germs gain the upper hand. You need to reduce these ‘bad’ bacteria in the mouth to prevent tooth decay, bad breath, gum inflammation or periodontal disease. Most bacteria in the oral cavity live mainly on the back part of the tongue; Bacteria and food remains (tongue coating) are present there. They can be reduced by brushing the tongue regularly. Suitable tools for this are a tongue scraper or a tongue brush. It is recommended to use it once a day. Alternatively, a clean spoon without sharp edges can help with tongue scraping. With all devices it is important that they never go too far back into the throat, otherwise a gag reflex will occur. Professional tongue cleaning at the dentist also reduces bacteria in the mouth. He uses special tongue suckers or an ultrasonic device to remove the tongue deposits.
Bacteria live not only on the tongue, but also on the oral mucosa, teeth, gums, on the necks of teeth or in the deep pockets. You can eliminate dangerous bacteria through good oral and dental hygiene and other measures:

  • Brush your teeth at least twice a day for two minutes or more and do this thoroughly. Combine brushing your teeth once a day with dental floss and toothpicks. These tools can be used to combat bacteria found on the gum line and in the spaces between the teeth.
  • Use disinfectant mouthwashes. Products containing fluorides (tin fluoride, amine fluoride) have an antibacterial and anti-inflammatory effect; they reduce the number of germs in the mouth, but are not a substitute for brushing your teeth. As the only remedy for problems with gums and teeth, a mouthwash can do nothing. It should always be combined with good brushing.
  • A professional dental cleaning at the dentist or dental hygienist also tackles stubborn bacterial plaque that is located in hard-to-reach places, such as the back molars, tooth necks or pockets. There are many bacteria that attack tooth enamel and cause inflammation in the gums. A professional dental cleaning is a great way to restore healthy oral flora. Depending on the dental situation, professional dental cleaning is recommended twice a year and more often in case of illness.
  • Have a dentist treat damage to your teeth such as cavities, defective fillings or open root canals. Otherwise, food waste will collect there, which in turn is an ideal breeding ground for bacteria. The same applies to inflammation of the gums (gingivitis) and periodontitis.
  • Nutrition: If you often eat sugary foods, the germs will find the best conditions to multiply. This applies to all bacteria that multiply from sugar from food waste. So reduce your sugar consumption or switch to products with sugar substitutes.
  • It is best not to smoke or consume too much alcohol. Such stimulants weaken the immune system in the mouth.
  • Stress weakens the body’s defenses, including the defenses in the mouth. This changes the composition of the bacteria and oral flora. The risk of periodontal disease increases. So try to control the stress in everyday life and at work. Relaxation exercises can help with this.
  • Metabolic diseases such as diabetes also affect oral health. Have such diseases treated appropriately.


Symptoms of a disturbed flora

Symptoms that the oral flora is out of balance include inflammation of the oral mucosa, gums and teeth. Symptoms may include:

  • Bad breath: there is deposits on the tongue in which bacteria multiply, the result is unpleasant bad breath and a bad taste in the mouth.
  • Aphthous mouth ulcers are painful injuries to the mucous membrane of the mouth. Canker sores can also appear on the tongue.
  • Abscesses in the mouth, purulent inflammation.
  • Sometimes fungi and bacteria in the mouth cause your tongue to feel burning if the microorganisms are out of balance.
  • Fungal infection of the oral mucosa when the yeast Candida albicans multiplies.
  • Herpes infections caused by herpes viruses.
  • Caries, when caries bacteria multiply rapidly; they attack tooth enamel and cause cavities; then the bacteria in the mouth cause symptoms such as toothache.
  • Root tip inflammation, an inflammation in the root tip of a tooth or molar.
  • Inflammation of the gums (gingivitis): the gums are red, inflamed and painful.
  • Periodontal disease: harmful bacteria penetrate deep into the structures that anchor the teeth and cause inflammation. Symptoms include receding gums, painful exposed tooth necks and, in the worst cases, tooth loss.


Remedies against bacteria in the mouth

Home remedies can reduce the number of germs in the mouth.

Yogurt or kefir

You can of course treat bacteria in the mouth with yogurt or kefir that contain lactic acid bacteria; These lactic acid products attack bacteria that break down proteins and thereby release sulfur-containing gases such as hydrogen sulphide and methyl mercaptan that smell like rotten eggs and give you bad breath.


The chlorophyll or chlorophyll from parsley, peppermint or wheatgrass juice repels bacteria that cause bad breath.

Sage, thyme and lemon

Sage and thyme have anti-inflammatory properties. Lemon is also good against bacteria.

Tea tree oil

Tea tree oil has an antibacterial effect; put a few drops of it in a glass of water and rinse your mouth with the solution. Then spit it out. Never put undiluted tea tree in your mouth!

Baking soda

Baking soda

A solution with salt or baking soda (baking soda) disinfects and combats harmful bacterial growth on the teeth.

Black and green tea

Black and green tea contain polyphenols, which have an antibacterial effect and slow the growth of plaque bacteria. The active ingredients are said to help with periodontitis and receding gums.

Oil pulling

Swirling oil in the mouth, for example olive oil or coconut oil, is said to eliminate bacteria in the mouth. Put a tablespoon of oil in your mouth, move it back and forth and also let it run along your teeth. The oil binds bacteria and other germs. Then spit the oil into a paper towel and throw it in the trash.

Marigold or calendula

Marigold (calendula) has a calming, anti-inflammatory effect and fights bacteria and fungi in the mouth. Make marigold tea and rinse your mouth with the solution.


The home remedy chamomile is also good against bacteria in the mouth. The ingredients have a soothing effect on the gums and are anti-inflammatory.


Highly disinfectant mouthwashes, which are commercially available, kill the unwanted putrefactive bacteria. Mouth rinses with chlorhexidine prevent the formation of plaque, but you should generally only use these rinses for a short period of time (usually 1 to 2 weeks).

Restore or improve oral flora

You can help rebuild the oral flora yourself. Your oral flora is crucial for the health of the mouth, gums and teeth. This means that tooth decay, inflammation of the gums or periodontal disease are less likely to occur. All products that combat bacteria in the mouth also help build up oral flora. The following measures are useful:


Oral flora-promoting preparations with beneficial bacteria are available at drugstores and online. Probiotics are available as tablets or lozenges. For example, if you use antibiotics, the oral flora is disrupted because the drugs eliminate not only pathogenic but also healthy bacteria. Probiotics can then strengthen the oral flora.


You can also restore the oral flora if you use the sugar substitute xylitol instead of sugar. The substance has a caries-inhibiting effect because it reduces plaque formation and slows down the growth of caries bacteria such as Streptococcus mutans. The bacteria have no food and become ‘starved’. Xylitol prevents tooth decay.

Hydrogen peroxide

Hydrogen peroxide has a disinfectant effect and kills many types of bacteria that occur in the oral cavity and can cause inflammation. Hydrogen peroxide has a strong antibacterial effect, kills germs and you can restore your healthy oral flora. Use hydrogen peroxide as long as you have complaints, but not for longer than 7 days in a row.

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