Mouth Bacteria: Promote the good bacteria and kill the bad ones

bacteria of mouth
You will be surprised if you learn how many microorganisms live in our bodies.
The number of bacteria exceeds even our cells, which shows their importance in our system.

The mouth alone hosts a large number of bacteria with more than 500 species, 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 bacteria are not necessarily bad. Most microorganisms in the oral cavity live in symbiosis. In other words, we have a reciprocally beneficial relationship with them.

Under certain conditions, the balance between these bacteria will be disturbed. The bad bacteria will dominate and cause problems.

The development of mouth bacteria: From fetus to adulthood

The fetus's environment is free of bacteria. However, some studies have concluded that certain bacteria found in the mother's gum disease can contaminate the amniotic fluid (the fluid that surrounds the fetus) and lead to complications such as premature birth and low birthweight.

Immediately after childbirth (less than 5 minutes), the baby's mouth will be contaminated by the mother's microorganisms.
Thus, babies born via vaginal birth will have an oral flora similar to that found in the mother's vagina, while babies born by Cesarean section have bacterial communities similar to those present in the mother's skin.
Some of these bacteria are temporary and will disappear with the acquisition of the permanent flora.

After a few hours, the baby's mouth will be contaminated by the external environment through breathing, breastfeeding and contact with parents and medical staff.
At this stage, the permanent oral flora begins to form.

The bacteria that have colonized the mouth will attract other bacteria to form complexes.

After a few months, the baby already has a diversified oral flora, mainly through food ingestion, contact with other adults, children, pets, and oral hygiene habits.

With the eruption of the first teeth (6 months), a new environment appears for the bacteria.
Cariogenic bacteria (or cavity-causing bacteria) such as Streptococcus mutans will begin to colonize the teeth as their preferred adhesion surface appears.

The space that forms at the gum line is a favorable environment for anaerobic bacteria (that are intolerant to oxygen). They are involved in gum disease.
This highlights the importance of oral hygiene practice in the baby.

At 3 years old, the oral microbiome is already complex. The maturation process continues until adulthood.

During this period, the bacteria live in harmony. However, this balance is fragile and can be disrupted by various factors leading to diseases, especially caries and gum disease.

Why does the mouth contain so many bacteria?

Bacteria are microorganisms that depend on their environment. The oral flora is rich and complex for different reasons:

Diversity of tissues in the mouth

The mouth offers different surfaces for bacteria to adhere to. The teeth will attract cariogenic bacteria while the gums will attract bacteria responsible for gum disease.
Remember that these bacteria live in balance and only under certain conditions do they cause disease.

Ensures the nutritional needs of bacteria

The mouth will ensure the nutritional needs of bacteria through the food debris trapped between the teeth, saliva and tissues.

The mouth temperature is suitable

During the day, the temperature of the mouth can vary from 0 to 60°C. This will ensure the survival condition of a large number of bacteria, hence the diversity of species in the oral microbiome.

The mouth humidity

Different types of fungi or bacteria require different amounts of water to reproduce and grow. In the mouth, this is provided by saliva.

Interaction and formation of complexes between bacteria

The presence of certain bacteria will attract other bacteria by promoting their adhesion and ensuring their nutritional needs through their secretions. This will lead to the formation of more resistant and sometimes very pathogenic bacterial complexes.

How bad bacteria affect us

We can divide the bacteria of the mouth into two groups: friendly flora which is beneficial for us, and pathogenic flora.

Normally, these two groups coexist harmoniously.
The imbalance between these two groups will be mainly manifested by caries and gum disease.

4 factors can disturb this balance:
  • Pathogenic bacteria in sufficient quantity,
  • Absence of "friendly" bacteria,
  • Bad oral environment (high acidity, dental plaque, tartar),
  • Weakened immune system.

Bacteria that cause tooth decay

Dental caries are the result of irreversible damage caused by bacteria through the acid they release.

When oral bacteria multiply and accumulate in the form of plaque, they can penetrate tooth tissue.

The bacteria associated with cavities is Streptococcus mutans. It is also the most common bacterium in dental plaque.

However, studies have shown that other bacteria are also associated, such as Lactobacillus, Veillonella, Bifidobacterium, Propionibacterium.

These microorganisms have a high capacity to metabolize the sugars in food, causing a very acidic environment that attacks the tissues of the teeth.

The increase in acidity of the mouth will apply a natural selection by sparing only the bacteria able to survive in an acid environment. The good bacteria will decrease while the cariogenic bacteria will increase, which will further increase the risk of cavities.

Bacteria that cause gum disease

Gum diseases are very common in the world. Gingivitis and periodontitis are gum diseases that cause inflammation of the tissues surrounding the tooth, leading to their gradual destruction, which may end in tooth loss.

In a healthy state, the gums host a benign bacterial flora, composed mainly of Lactobacilli, Streptococci, Actinomyces, which ensures the health of the gums and protects them from pathogenic bacteria.

When the level of these "good bacteria" decreases, the balance is broken and pathogenic bacterial complexes develop, mainly composed of Porphyromonas gingivalis, Tannerella forsythensis and Treponema denticola.

Dental appliance and oral flora

Dental appliances, especially braces, can disturb the oral flora. They are associated with cavities risk and the aggravation of gum disease.

Among the effects of braces on the oral flora:
  • An increase in bacterial plaque, which is the main cause of gingivitis and cavities.
  • Contribution to bacterial diversity and interactions.
  • Increase in pathogenic bacteria in the mouth.

A study was conducted to evaluate the link between orthodontic appliances and bacterial colonization.

Metallic brackets in use for 1 month were multi-colonized by several bacterial species, including cariogenic microorganisms and periodontal pathogens, reinforcing the need for meticulous oral hygiene and additional preventive measures to maintain oral health in orthodontic patients.

Oral flora and cancer

An association between oral microorganisms and cancer has been suggested relatively recently.
Some microorganisms can transform alcohol into a carcinogenic substance called acetaldehyde.
People with poor oral hygiene have higher levels of acetaldehyde than those with better oral hygiene and even more so in heavy drinkers.

Similarly, smoking increases salivary acetaldehyde levels, adding to the risk from alcohol, making the effects of smoking and alcohol consumption on cancer development synergistic.

Hormones and oral flora

The hormonal change that occurs, for example, during puberty, menstruation or pregnancy leads to an increase in some groups of oral microorganisms that are highly involved in gum disease.

This change in the oral microbiome may be associated with the increased incidence and severity of gingivitis during these periods.

How do friendly bacteria protect us?

Not all bacteria want to harm us. Some of them are there to protect us from bad bacteria.

Streptococcus mutans are known to cause cavities. They are mostly found in dental plaque.

Bacteria able to cause gum disease include Porphyromonas gingivalis (Pg) and aggregatibacter actinomycetemcomitans (Aa). They are can penetrate deep periodontal tissues and cause inflammation.

Some bacteria found in dental plaque can inhibit these pathogenic bacteria through a substance called hydrogen peroxide.

Among them are S. sanguinis and S. oligofermentans which can release hydrogen peroxide and thus protect our tissues from these bad bacteria.

Other protective bacteria include S. cristatus which can bind to Pg and prevent it from colonizing gum tissues and S. sanguinis, S. mitis and S. salivarius which can prevent the colonization of Aa.

The aggression of these friendly bacteria will affect our oral health because of their protective role. It is then necessary to maintain this healthy flora to prevent oral diseases.

The study of these bacterial interactions has also brought attention to the use of probiotics as a means of treatment.

Probiotics are live microorganisms that are intended to have health benefits when consumed or applied to the body. In the mouth, they strengthen the good bacteria and compete with the pathogenic ones.

They can then disrupt the formation of dental plaque and prevent bad bacteria colonization.

A study has shown that individuals who ate certain fermented cheeses and yogurts (sources of probiotics) had significantly less gum disease.
This can be explained by the fact that they certainly seeded good bacteria from their food. However, stopping these foods will also stop the effects.

How to support good bacteria and kill bad bacteria

The characteristics of the oral flora depend on our genetics but also on our oral hygiene, our diet, our age and our health.

We can't change our genetics but some solutions allow us to promote the good bacteria and eliminate the bad ones. Among them:

  • Brush your teeth twice a day with a soft bristle brush and floss your teeth daily to remove all the dental plaque, which is a good niche for harmful bacteria.
  • Have a scaling once a year if you have healthy gums and 2 to 4 times a year in case of gingivitis and/or periodontitis.
  • Eat a balanced diet. Incorporating more vegetables and reducing animal products may help promote a balanced oral microbiome and overall health.
  • Reduce your sugar intake and acidic beverages as they promote the growth of Streptococcus mutans which contribute to cavities and periodontal disease.
  • Avoid smoking and excessive alcohol consumption. Research has shown that their effects are synergistic in disrupting oral flora and leading to oral cancer.
  • Are you diabetic? Check your blood sugar level, as it has a direct effect on the balance of oral flora. High blood sugar levels will attract bad bacteria and have a bad effect on the blood flow of the gums, which can increase your gum disease risk.
    Reciprocally, gum disease harms blood sugar balance. Therefore, good oral health is essential for diabetics.