The mouth is one of the most diverse habitats of the human body.
It contains more than 700 known species of bacteria, as well as yeasts, viruses and some protozoa.
This community is collectively known as the oral microbiome, and like the gut microbiome, bacteria in your mouth play an important role in health.
Some of the most common diseases caused by changes in the oral microbiome are cavities and gum disease (periodontitis).
But growing evidence suggests that the oral microbiome is also linked to many other serious health conditions that occur elsewhere in the body.
1. Respiratory disease
Since the respiratory tract begins in the mouth and ends in the lungs, it is perhaps not surprising that an overgrowth of the oral microbiome can cause these microbes to be inhaled into the lungs.
This often leads to infections such as pneumonia, an often fatal disease in the elderly that has been linked to poor oral hygiene, causing an overgrowth of oral bacteria such as Streptococcus pneumoniae and Haemophilus influenzae.
Research has even shown that introducing regular oral hygiene practices and professional dental cleaning in nursing homes can reduce the number of pneumonia cases by a third.
It is also important to keep dentures and mouth guards clean.
Poor oral health has also been linked to chronic obstructive pulmonary disease (COPD) and poorer respiratory function, and this is linked to changes in the oral microbiome.
2. Heart disease
One of the most common oral microbiome diseases is chronic periodontitis.
This is an aggressive inflammatory response that destroys the bone and tissues that support the teeth, eventually resulting in tooth loss.
This disease is caused by an overgrowth of bacteria that thrive in the space between the gums and teeth due to poor oral hygiene.
But what has baffled researchers for years is the strong association between gum disease (gingivitis and periodontitis) and cardiovascular disease.
The link may be due to common risk factors. For example, gum disease and heart disease are more common among smokers.
Others have theorized that bacteria that cause gum disease could travel to the heart and cause an infection.
No convincing evidence of this link has yet been presented.
Gum disease also triggers a strong inflammatory response from the immune system.
Inflammation is the body’s way of tackling infections.
This results in the production of immune cells and chemical signals that fight infections.
But too much inflammation can be harmful. Some researchers think that the inflammation caused by gum disease could damage the cardiovascular system.
One study showed that treating gum disease reduced levels of inflammation in the bloodstream and significantly improved arterial function.
Other studies have also shown that treating gum disease reduces overall levels of inflammation in the body.
These studies demonstrate how a disease in the mouth can have significant effects on tissue function in other parts of the body.
And considering that many people live with untreated gum disease for decades, the potential for long-term health impacts is significant.
3. Colon and rectal cancer
Oral bacteria are known to travel through the stomach to the intestines.
Generally, our oral microbes are not well adapted to this new environment and usually die.
But in 2014, two studies showed that some types of colon and rectal cancer were heavily colonized by a species of bacteria called Fusobacterium which is normally found in dental plaque.
Both studies also showed that the Fusobacterium has a high attraction to malignant cancer cells.
This is because the surface of cancer cells allows the bacteria to firmly attach to and invade the tumor.
Multiple studies have now confirmed that Fusobacterium can colonize tumors throughout the gastrointestinal tract.
Research has also shown that patients with colon cancer heavily colonized by Fusobacterium They respond worse to chemotherapy and have a shorter life expectancy compared to those who are not colonized.
This may be because tumors infected with Fusobacterium They are more aggressive and therefore more likely to spread compared to those who are not infected with the bacteria.
Research is being done into this relationship and into whether people at risk for colon and rectal cancer could be vaccinated against this oral microbe.
4. Alzheimer’s disease
One of the most controversial links between oral health and disease has to do with Alzheimer’s disease.
Periodontitis has been associated with greater cognitive impairment in people with Alzheimer’s disease.
But since both periodontitis and Alzheimer’s are associated with aging, it is difficult to determine whether there is a clear cause-and-effect relationship.
In 2019, researchers presented evidence that the brains of people with Alzheimer’s disease were colonized with P gingivalisone of the main bacteria that cause gum disease.
The idea that the brain, a normally sterile part of the body, can be infected by oral bacteria remains highly controversial and requires more research.
As with heart disease, inflammation caused by gum disease has also been proposed as a driver of Alzheimer’s disease in patients with poor oral health.
Good oral health
Although the impact of poor oral health seems overwhelming, the good news is that we have the power to manage our oral microbiome and prevent oral diseases.
A good oral hygiene regimen is essential. This includes brushing your teeth twice a day and flossing regularly to control plaque and reduce the incidence of cavities and gum disease.
If you smoke, quitting can greatly reduce your chances of developing gum disease.
It’s also worth visiting your dentist or hygienist every six months for a professional cleaning and personal oral hygiene advice.
All of this work will not only improve your smile, it can even add years to your life.
*Gary Moran is Associate Professor of Dental Sciences at Trinity College, Dublin. This article appeared on The Conversation. You can read the original version in English here.
Keep reading:
* The correct way we should brush our teeth
* Everything that the mouth reflects about our health
* 3 dental diseases that you can transmit through kisses
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