Gary Moran is an associate professor of dental medicine at Trinity College Dublin. Our mouth is one of the most diverse habitats in our body: it houses over 700 species of bacteria, as well as yeasts, viruses, and a number of protozoa. This microbial community is known as the oral microbiome, which, like the gut microbiome, can influence our health.
The most common diseases caused by changes in the oral microbiome are tooth decay and gum diseases. However, over the years, scientists have discovered many clues suggesting that the oral microbiome is also linked to many other serious problems that manifest elsewhere in our bodies.
Respiratory Diseases
The respiratory tract starts in the mouth and ends in the lungs. Therefore, it is not surprising that when the oral microbiome proliferates, some of the microbes can be inhaled and end up in the lungs. This often leads to pneumonia. The risk of developing this infection, which is often fatal in the elderly, has been associated with poor oral hygiene, which leads to the proliferation of certain bacteria such as Streptococcus pneumoniae and Haemophilus influenzae.
Studies have shown that improving oral hygiene in nursing homes and providing dental care by professionals can reduce the number of pneumonia cases by a third. It is also important to ensure the cleanliness of dental appliances and other oral devices (mouthguards for athletes, for example).
Some research has also shown an association between poor oral health and chronic obstructive pulmonary disease (COPD), as well as alterations in respiratory function, due to changes in the oral microbiome resulting from such a situation.
Heart Diseases
Chronic periodontitis is one of the most common conditions due to the oral microbiome. This disease results from the proliferation, due to inadequate oral hygiene, of bacteria between the gums and teeth. It is characterized by a destructive inflammatory response that attacks the bones and tissues supporting the teeth, leading to loosening and loss of teeth.
Researchers have observed a significant statistical association between periodontitis and cardiovascular diseases over the years. This could be explained by common risk factors between these different conditions. Thus, periodontitis and heart diseases are both more common in smokers.
Another hypothesis is that bacteria from periodontitis could be capable of moving to the heart and causing an infection. However, scientists are currently trying to elucidate the mechanisms that may be at work.
As mentioned earlier, periodontitis triggers a strong inflammatory response. It is important to note that inflammation is one of our body’s ways to fight infections: it involves the production of cells and various chemical signals necessary for the proper functioning of the immune response. But too much inflammation can be harmful. According to some researchers, the inflammation caused by periodontitis could damage the cardiovascular system.
A study has shown that treating periodontitis reduces inflammation levels in the blood and greatly improves arterial function. Other studies have also shown that treating periodontitis reduces overall inflammation levels in the body.
These studies demonstrate that oral disease can have significant effects on the function of tissues located elsewhere in the body. Since many people live with untreated periodontitis, sometimes for decades, the deleterious effects on their health can potentially be major in the long term.
Colon Cancer
Oral bacteria are capable of traveling through the stomach to the intestines. Generally, the microbes that usually live in the mouth are not well adapted to these new environments, and they die quickly. However, in 2014, two studies showed that colon cancer tumors were highly colonized by a bacterium species called Fusobacterium, which is normally found in dental plaque.
These studies also showed that Fusobacterium has a strong affinity for malignant cancer cells. This bacterium is indeed capable of tightly binding to the surface of cancer cells and invading the tumor. Since then, multiple studies have confirmed that Fusobacterium can colonize tumors throughout the gastrointestinal tract.
Research has also shown that patients with colon cancer heavily colonized by Fusobacterium respond less well to chemotherapy and have a shorter life expectancy compared to those who do not have this colonization. This could be due to the fact that tumors infected with Fusobacterium are more aggressive and therefore more likely to spread than those not infected with this bacterium.
Research continues to better understand this relationship, and to determine if people more susceptible to colon cancer could benefit from a vaccination against this oral microbe.
Alzheimer’s Disease
One of the most controversial links between oral health and pathology concerns Alzheimer’s disease.
In individuals with Alzheimer’s, suffering from chronic periodontitis is associated with a greater cognitive decline. However, since periodontitis and Alzheimer’s disease are both associated with aging, it is difficult to determine if there is indeed a cause-and-effect relationship.
However, in 2019, research revealed that the brains of people with Alzheimer’s disease were colonized by Porphyromonas gingivalis, one of the main bacteria responsible for periodontitis. The fact that the brain, an organ normally preserved from microorganisms, can be infected by oral bacteria remains highly controversial, and further research on this topic is needed.
Furthermore, as in the context of heart diseases, some specialists have also suggested that the inflammation caused by periodontitis in patients with poor oral health could be an exacerbating factor for Alzheimer’s disease.
The Importance of Good Oral Health
Poor oral hygiene can have multiple deleterious consequences on health. However, it is possible to control your oral microbiome and prevent related diseases.
For this, it is necessary to establish a daily oral hygiene routine. This includes brushing your teeth twice a day, as well as regularly using dental floss to limit plaque and reduce the incidence of cavities and gum diseases. When it comes to gum diseases, quitting smoking greatly reduces the risk of their occurrence. It is also advisable to see a dentist at least once a year for scaling and to receive advice from a professional.
Following these recommendations will make your smile brighter and could also extend your life expectancy by a few years…
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