Dentists and doctors. Doctors and dentists. We train these health professionals in separate and distinct traditions as if the work of one had little to do with the other.

Hippocrates, the Father of Western Medicine, saw things differently 2,400 years ago. He treated many types of bodily infections by pulling bad teeth. Today, researchers are discovering that Hippocrates was definitely on to something.

The mouth, it turns out, is… part of the body! It’s a gateway, through which good things and not-so-good things enter the digestive tract, the bloodstream, and the respiratory system. What happens in the mouth, doesn’t stay in the mouth.

It’s also a window, offering lots of clues about things going on elsewhere in the body. This two-way flow of cause and effect, as we learn more about it, provides new opportunities for improving the treatment and diagnosis of a growing range of health issues.


Our mouths are home to a busy community of microorganisms. Hundreds of different species of bacteria, viruses, fungi, and protozoa reside on the various types of surfaces inside the oral cavity. But before you run for the Listerine, stay calm and keep reading.

In a well-tended mouth, there’s less variety of bacterial species, and these are mainly friendly ones. They keep the unfriendly species out of the neighborhood. Poor hygiene disturbs this ecological balance and allows pathological species to multiply and then dominate. These are the bacteria that ferment carbohydrates, such as sugars, and secrete the acids which eat away at our enamel. This causes tooth decay and cavities, probably the most common infectious disease of the human race.


As their colonies grow these unfriendly bacteria can bring on the other common type of oral pathology. Gingivitis and periodontitis are immune-inflammatory diseases which attack the gums, and if allowed to progress, the bone supporting the teeth.

People often overlook gingivitis, which is unfortunate since it is relatively easy to treat. It’s not usually painful, so it’s not hard for us to ignore the symptoms of reddish and swollen gums, and perhaps some bleeding when we brush and floss. The good news is gingivitis is easily identified by dentists and dental hygienists. Whether the bad breath (halitosis) gingivitis can cause is also good news is a matter of opinion, but if this is what motivates us to get with the dentist it can’t be all bad.

Periodontitis is the unhappy final chapter in this process of infection. Receding gum lines and bone loss are the results of bacteria concentrating in pockets formed in the gums. Chronic inflammation triggers the body’s immune system to fight back, and the battlefield suffers destruction.

The key word in this scenario is “infection”. Cavities and periodontal diseases are caused by infection. Let’s now go over what we know and what we’re learning about the connection between oral infections and general health.


Systemic diseases are conditions that involve the entire body, or at least large parts of the body’s systems.
Full disclosure: researchers have not yet produced conclusive proof that periodontal disease is the exclusive cause of any systemic disease. That said, there is a great deal of scientific evidence for correlations between oral infections and numerous systemic conditions. The fact that two conditions are often or even always seen together doesn’t tell us which caused which, or even that one caused the other. It could be that a third factor, known or unknown to us, caused them both. It could be that they cause each other, in a vicious circle.

Even without certain knowledge of cause and effect, there’s a lot of value in knowing about the connections we’ve found between your oral health and all the rest of you.


Bacterial endocarditis is an infection of the inner lining and the valves of your heart. Some of the bacteria species that cause periodontitis also cause endocarditis, and there’s a high level of confidence that these bacteria reach the heart by riding the bloodstream from colonies in the mouth. We noted that brushing and flossing with periodontal disease often cause bleeding, and that’s a sign the bloodstream is open to bacteria.

Bacterial endocarditis is a serious, sometimes fatal disease. Treatments include long courses of powerful antibiotics delivered intravenously, and heart surgery is sometimes required. Not a very common complication of oral neglect, but a very terrible one.


The case for oral infections as a cause of cardiovascular diseases such as atherosclerosis (clogged arteries) grows stronger as more studies explore the long-accepted correlation between the two. In addition to the body’s reactions to the chronic inflammation of periodontitis, scientists are zeroing in on substances called endotoxins. These endotoxins appear to migrate from the outer membranes of the guilty bacteria into the bloodstream, where they cause injury to blood vessels.


The diabetes-periodontitis relationship is now known to be a case of two-way cause and effect. Diabetes can reduce a patient’s resistance to infection, including oral infections, and patients with oral infections find it more difficult to control blood sugar levels. Studies have demonstrated that periodontal treatment of diabetic patients improves their blood sugar management.


The list of systemic diseases that research has linked to oral infection is long and growing longer, and study of the cause-and-effect relationships continues. Pathologies of the kidneys, lungs, bones, and brain have all been linked to periodontitis. So, too, have birth weight and complications of pregnancy.
It may seem interesting, but not very useful, to know only that a systemic disease is correlated with oral health. After all, you ask, what can be done to help a patient if we don’t know which way the arrow of cause points?


This brings us back to our observation that the mouth is a part of the body. The extent of this unity is dramatically illustrated by the increasing variety of saliva tests, which now include diagnostic analysis for HIV, hormones such as cortisol, pancreatic cancer, hepatitis, testosterone, amoeba parasites, and C-reactive protein, among many others. Preliminary findings suggest saliva testing may soon be available for diabetes, Parkinson’s disease, and cirrhosis of the liver.

Whether or not periodontal infection causes any of these ailments, or is caused by them, doesn’t alter the basic truth that an infection in the mouth is a health issue that needs to be taken seriously.

For you and for all of us, the moral of the story is clear. Dental health is essential health. We shouldn’t neglect it any more than we’d neglect the health of any of our body’s organs or systems, because they’re all connected. We should keep our doctors appraised of our dental situation, and keep our dentists up to speed on our medical status. We’re all on the same team.