More Oral-Systemic Connection Evidence? Mouth Bacteria Found in Stroke Victim Brain Clots

Emerging science and evidence have begun to lift the veil on complex, interconnected relationships between the health and biome of the oral cavity and the health of the rest of the human body.

This relationship has been deemed the “oral-systemic connection,” and we have already identified numerous diseases and conditions that have been tightly correlated with high oral bacterial loads and poor oral/gingival hygiene and health.

  • Gum disease has been linked to heart disease and other cardiovascular system conditions such as atherosclerosis and stroke
  • Diabetes is more statistically likely when oral health suffers
  • Pregnancy complication rates are elevated among women with gum disease
  • Alzheimer’s disease and some cancers occur more frequently in those with gingivitis

The latest research, emerging from a study conducted by a group in Finland that has been pursuing evidence of the oral-systemic connection for a decade, evaluated blood clots removed from the brains of 75 patients who had been treated from ischemic strokes (the type of stroke caused by a clot in the brain—87% of strokes are the ischemic type, versus hemorrhagic strokes, caused by a ruptured blood vessel and uncontrolled cranial bleeding without an initiating clot).

The results of the study were remarkable: 63 of the clots (84%) removed from the brains of these stroke patients contained DNA from viridans streptococci bacteria, normally found in the mouth.

Researchers already know this type of bacteria can travel from the oral cavity to the bloodstream and cause infections, including endocarditis—inflammation and enlargement of the tissues of the heart, including its muscles or lining. The new study’s authors had already found this type of bacteria in the blood clots of patients who had experienced heart attacks earlier, in 2013.

Still, the American Heart Association isn’t moving rapidly to revise its stance on the oral-systemic connection. The last time it convened a panel to review the evidence of ties between gum disease and heart disease, the group declined to conclude the evidence at the time was strong enough to prove a direct link; in a classic reformulation of “correlation does not prove causation,” the lead author of AHA’s position statement cautioned, “Finding evidence of bacteria in blood clots doesn’t mean they have a role in the disease process.”

Nonetheless, as more studies continue to emerge, evidence continues to build. It’s hard to imagine the harm that might come from pre-clearance, antibiotic prophylaxis, and collaboration among health providers before and after invasive dental/endodontic procedures.

As the lead author of the current study put it: “Our results suggest that bacteria might have a role in the [development] of serious complications related to atherosclerosis”—and until we know differently, the safest course for dentists, hygienists, and patients is to proceed with appropriate oral care and hygiene as though bacteria in the mouth may travel everywhere during and after procedures.