Bacteria of mouth: An enemy of our Oral Health

bacteria of mouth

Did you know that we are only 10% human and 90% bacteria ? Our body contains 10 times more bacteria than our cells. For each human cell there are around 10 bacterial cells.

The mouth is the dirtiest part with more than 500 different genera and species, more than 100 bacteria per cell, 1 million bacteria per 1 ml of saliva and 100 millions bacteria per 1 mg of dental plaque.
In the normal state, these bacteria serve us; they help us in digestion, provide us with essential nutrients like vitamins, maintain our immune system and protect us from other pathogenic bacteria.
Bacteria in the mouth change from birth to adulthood by different factors.

Does this change make our bacteria aggressive, or, on the contrary, it makes them more beneficial to us?

Bacteria of mouth: Modification from birth to adulthood

Before birth, the oral flora does not exist or very little. Afterwards, the baby's mouth may be contaminated by certain bacteria because of contact with the external environment.
Indeed, it is only from the 4th day that oral flora will be formed. The beginning of this colonization is essentially done by the contact with the mother (during breastfeeding) and contaminated objects.
From 0 to 6 months, some bacteria are present temporarily in the baby's mouth, while others are already permanently colonizing his mouth and tongue. This first colonization is authorized by the immunological immaturity of the infant. The baby at this age does not have teeth. The flora of his mouth is composed only of bacteria able to attach to soft surfaces (tongue, cheek, gum).
Later, as the years go by, the complexity of bacteria of mouth increases.
From 6 months, this flora will change again because of the eruption of the first teeth that offer a new type of surface for bacterial colonization.
The gap between tooth and gum created by eruption of teeth represents a new habitat for bacteria of mouth. It helps to increase the growth of anaerobic bacteria responsible for periodontal diseases.
Subsequently, other bacterial species colonize the tooth surfaces. Some of them are capable of causing dental caries after an imbalance of the natural oral flora.

Bacteria of mouth modification: Is it bad for us?

Bacteria of the mouth are essentially commensal; it represents all the bacteria found in the healthy state.

Not only do commensal populations not cause us damage, but also, they protect us from bacteria that can damage our tissues by preventing them from colonizing our tissues. They have a protective role, they are able to protect us from dental diseases.
However, in certain conditions (alteration of immunity, hormonal modification, diabetes, unbalanced diet, insusceptible oral hygiene) bacteria that are part of the normal oral flora, will be attacked by aggressive bacteria. These will multiply and become dominant. This excessive proliferation will lead to the increase of toxins, enzymes and bacterial pathogenic substances, hence the appearance of dental diseases.
In short, the modification of bacteria of mouth can be harmful only if it is caused by the individual himself.
We adopt behaviors by which we attack our natural flora without realizing it. Among these behaviors we find: smoking, excessive consumption of sugar, snacking, poor oral hygiene, uncontrolled diabetes.
However, the change of the oral flora in relation to the growth of the child is a natural process. As our tissues and organs mature, the bacteria that live in us will also adapt to their environment to be able to live without damaging us in the absence of external factors.

Why our mouth is the dirtiest part of our body ?

The mouth is the dirtiest part of our body with more than 500 different species of bacteria, more than 100 bacteria per cell, 1 million bacteria per 1 ml of saliva and 100 million bacteria per 1 mg of dental plaque. These huge numbers leave us wondering why the mouth is the germiest part of our body.
Many factors favor the colonization of bacteria in our mouth:

Rest of food

The mouth ensures the nutritional needs of the bacteria by different means. The rest of the food stuck on the teeth and gum is a good food source for the bacteria. Saliva and tissues of the mouth provide other nutrients essential for bacteria.

Temperature of mouth

Large temperature variations can be observed in the mouth and can range from 0 C to 60 C. These will help ensure the necessary survival conditions of many microorganisms, hence the gender diversity of bacteria of mouth.

Diversity of surfaces of the mouth.

The mouth is composed of 2 types of surfaces: The hard surface which represents the tooth, and the soft surface which represents the gum. The mouth will recruit bacteria able to attach to the hard surfaces responsible for caries, and bacteria capable of attaching to the gum responsible for gum disease.


Humidity is a necessary survival condition to certain bacteria. The mouth being wet will allow the bacteria to grow quietly under the necessary conditions.
This species diversity will allow bacteria to interact and make connections. In fact, the bacteria will help each other to live even in the most difficult conditions. Plaque is a form of these interactions.

dental plaque

How bacteria can cause Dental Disease ?

As we have already seen, a simple imbalance of the oral flora caused by the individual (behavior) or the environment is enough for bacteria that were our friends to become our worst enemies. Bacteria of the mouth are responsible for 2 diseases: cavities and gum diseases.


Dental caries is a disease of bacterial origin, occurring after the eruption of teeth. It is accompanied by a destruction of the tissues of the tooth and evolves towards the formation of a cavity.
It has been shown that the ingestion of carbohydrate causes in a few minutes the elevation of the acidity in the mouth. The bacteria responsible for cavities use these carbohydrates to produce acids that will be responsible for demineralization of the enamel (the external surface of the tooth).
When acidity increases, the enamel is demineralized. In its initial stage, it is easily treated, but, if nothing is done, the demineralization will evolve towards the formation of a cavity requiring a surgical treatment.
In addition, the acidity produced by these bacteria will make the environment favorable only for their growth, and not for the natural flora that is supposed to protect us. Thus, the process of demineralization will be more and more rapid and will tend to evolve towards the internal tissues of the tooth (pulp).

Periodontal diseases

Periodontal disease is a very common disease in the world. At first, it reaches only the gum, but if no treatment has been considered, it can progress to the deepest tissues (bone, root of the tooth).
It has been shown that most bacteria capable of causing gum disease are anaerobic bacteria, which means that their growth is conditioned by an environment where there is very little oxygen.
The space between the gum and the tooth being very narrow does not let the oxygen pass which presents a favorable environment for the growth of anaerobic bacteria capable of colonizing the periodontal tissues (which surround the tooth).

How to reduce the number of aggressive bacteria ?

The best way to limit the number of pathogenic flora is to maintain good dental hygiene; brush your teeth at least twice a day for 3 minutes and use an interdental instrument (floss, oral irrigator) to control the plaque that forms between the teeth.
Mouthwash is highly recommended in case of gum disease, it reduces the inflammation of the gums and promotes its healing.
It is best to get rid of the behaviors that ruin our oral health such as smoking, nibbling between meals, excessive sugar consumption, forget to brush your teeth after meals.
It is also necessary to control the general health. As we have seen, there is a relationship between the state of general health and oral health. For example, diabetics are more likely to develop cavities and periodontal disease than normal people. Also, diseases that are related to hormonal modification are a huge risk factor for gum disease.
It is therefore necessary to control the general health, balance the diet and maintain good hygiene.
And do not forget, take care of your mouth and your natural flora for better oral and general health.