This article released by the National Institutes of Health explains a study, published in the journal Circulation and supported by four agencies of the NIH, reports that periodontal bacteria are a strong, possible precursor for the development of cardiovascular disease.
Cardiovascular diseases are usually influenced by atherosclerosis, a common arterial disease in which raised areas of degeneration and cholesterol deposits, called plaques form on the inner surfaces of the arteries, making the arteries thicker and hindering the proper circulation of blood to organs. This  disease predisposes the person to myocardial ischemia, also known as heart attacks and strokes.
This study found that certain bacteria found in the mouth can be one of the precursors for cardiovascular disease, as researchers state that these persons had thicker carotid arteries. Bacterial infection from an oral origin may enter the main blood circulation and affect the heart and other major organs.
Although researchers have yet to establish the correlation that periodontal bacteria directly causes cardiovascular disease, the authors write that there are currently studying four specific bacteria to determine the specificity of the association.
The lead author, Moïse Desvarieux, M. D., Ph. D., an infectious disease epidemiologist at Columbia University’s Mailman School of Public Health and the University of Minnesota, elaborates that in their studies and experiments, they tested the oral bacteria and carotid thickness of each of the 657 subjects, with factors such as smoking and diabetes, which largely influence thickened arteries, aptly controlled. They found that it was next to impossible to determine whether the periodontal disease or the thickening of the carotid arteries came first. Therefore, causality cannot be firmly established.
Another author of the paper, Ralph Sacco, M.D., M.S., associate chair of Neurology, professor of Neurology and Epidemiology, and the director of the Stroke and Critical Care Division of Columbia University College of Physicians and Surgeons, state that they will re-test the subjects in less than three years to see if the progression of the atherosclerosis of the carotid arteries in relation to ongoing periodontal disease, to hopefully get a better understanding of the time frame of the disease and to verify if indeed one is the cause of the other.
The article states that an average person carries varying quantities of bacteria in the mouth, but not all of these bacteria prove to be harmful. The researchers are determined to find out if increased proportions of the so-called ‘bad bacteria’ relates to a higher incidence of thickened carotid arteries. The four kinds of bacterial pathogens that stood out were Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola. However, David Jacobs, Ph. D., another author and a professor in the Division of Epidemiology at the University of Minnesota School of Public Health adds that they found an exception, a bacterium called Micromonas micros, which carried significant weight in the close relationship of periodontal disease and cardiovascular disease.
The researchers, out of their studies and experiments are confident that their hypothesis has received some merit, but it is essential for them to continue on doing further research to prove the causality for sure.  Read more on this article