Periodontitis is Not Just a Disease of the Mouth

A new understanding of the oral microbiome is shedding light on the relationship between periodontitis and systemic diseases, such as CVD, COPD, and cancer.

The mouth contains one of the most important microbiomes of the human body. It is home to some 700 different species of bacteria that live in different microbial sub-habitats:

While the mouth is one of the most vital body parts for our health, its significance is often overlooked. In fact, despite my background as a clinical dentist, even I was surprised as I delved into the research on the relationship between periodontitis and systemic diseases, such as cardiovascular disease, COPD, and cancer.

The mouth is the first point of contact for microbes

However, while a high level of species diversity within the GI tract is correlated with better health, oral is associated with higher diversity and richness of microbe species.

Good oral health is ensured by maintaining the homeostasis of a relatively limited number of microbe species living within the mouth.

Disturbing the Balance

A new understanding of the oral microbiome is shaping how we think about oral health and disease in relation to some systemic diseases. So far, three pathways linking oral infections to secondary systemic effects have been proposed.

1. Metastatic Infection: Transient bacteria from oral infection or dental procedures can gain entrance into the blood and circulate throughout the body. Disseminated microorganisms may find favorable conditions, settle at a given site and start to multiply, colonize and infect the new site.
2. Metastatic Injury: Certain bacteria can produce toxins that, when excreted or otherwise introduced into a host body, can trigger many pathological manifestations.
3. Metastatic Inflammation: Proinflammatory molecules that enter the bloodstream from oral tissues may react with circulating antibodies to produce large complexes that give rise to acute and chronic inflammatory reactions. ( )

We can gain a more concrete understanding of these mechanisms by looking specifically at the second most common oral disease in the world: periodontal disease, which also called periodontitis. It may surprise you to learn that this common oral disease has connections to many systemic diseases, such as

Introduction to periodontal disease

Anaerobic bacteria found in invasive microbial plaque can penetrate gingival tissues in the gums. When this happens, it can induce tissue destruction as well as inflammatory responses from cells such as lymphocytes, macrophages, leukocytes, and other cells with crazy names that are associated with the immune system. These cells act to protect your body from foreign pathogens.

In other words, a periodontal lesion is like a rotting fruit hidden in the trunk of your car. At first, you may have no idea that there is an old banana sitting in the corner of your trunk underneath a pile of shoes.

However, if left to sit, the once healthy banana will turn into a brown lump of mush that will attract fruit flies, in the same way that the bacteria in periodontal lesions elicit an immunological response. If the rotting banana is still not attended to, then the normal progression of any food item that is left out will follow. The smell of decay will inevitably permeate the entirety of the car.

Periodontitis and cardiovascular disease

Periodontal disease itself is treatable through surgical procedures that involve removing plaque and tartar from the teeth and root surfaces. Relating back to the rotting fruit analogy, once the source of the smell is found, it too, can be cleaned and managed.

However, the smell will still remain for quite some time after, similarly to the way periopathogenic bacteria will remain in the body due to dissemination via the circulatory system. This can lead to increased risk of certain systemic diseases, including cardiovascular disease, as well as prompt reinfection of the gums.

Researchers have linked periodontitis to cardiovascular disease by corroborating associations between specific bacteria (consistent with periodontitis) and coronary diseases developing as a result of atherosclerosis.

Theories about pathogenic oral bacteria and cardiovascular disease

The exact mechanism by which pathogenic bacteria involved in periodontal disease (such as Porphyromonas gingivalis, Helicobacter pylori, and Prevotella intermedia) influence the thickening of arterial walls is still in the hypotheses stage. It is proposed that the migration of such microbes into the circulation system can lead to a direct invasion of arterial walls.

Periodontitis and chronic obstructive pulmonary disease

Due to the close proximity of the oral cavity to the respiratory tract, perhaps it is easier to see how pathogens in the mouth can affect the lungs rather than the heart. In fact, recent epidemiological studies have shown that there is an increased risk of chronic obstructive pulmonary disease (COPD) as a result of inflammatory responses to certain periodontal pathogens (such as P. gingivalis) .

Periodontitis and Cancer

Research on this topic is still in the early stages, but the basis on which it stands still traces back to bacteria involved in periodontal disease and, ultimately, an imbalanced oral microbiome.

The bottom line

Periodontitis is not just a disease of the oral cavity. It has links to serious systemic diseases, such as cardiovascular disease, chronic obstructive pulmonary disease, and cancer. Although, we don’t fully understand the exact mechanisms involved, here is one thing we do know:

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Ellen M.Martin and Hailey Motooka were co-authors on this story. Click on the link to learn more about them.