Dental plaque to Arterial plaque - Does gum disease cause heart disease?

Dr Nameirakpam Anthopia *

Inadequate removal of plaque caused a build up of calculus (dark yellow color) near the gums on almost all the teeth. :: Pix - Wikipedia

Gingivititis is the inflammation of the gum following a microbial infection. Progress of gingivitis to involve the supporting tissues of the tooth (periodontium) leads to periodontitis. Periodontitis is characterized by bleeding and swollen gum, apical migration of the gum, and mobility of the involved tooth as a result of loss of soft tissue and bony support of the tooth. The source of microorganisms which cause periodontitis is the dental plaque which is a biofilm in which group of microorganisms adhere to each other on the tooth surface. 1,000 out of the 25,000 species of bacteria present in the oral cavity are involved with the formation of the dental plaque. The group of bacteria identified as causative organisms in periodontitis are Actinobacillus actinomycetemcomitans , Porphyromonas gingivalis, Bacteroides forsythus, Treponema denticola, T. socranskii, and P. intermedia.

A lot many people have linked gum disease, or periodontitis, to an increased risk of atherosclerosis and cardiovascular disease (CVD). The link impresses many as these conditions share common drivers such as inflammation. It is well known that even mild manipulation of the periodontal tissues, such as occurs during chewing or scaling causes translocation of bacteria from the dental plaque biofilm through the ulcerated epithelium of the periodontal pocket into the circulation resulting in bacteremias. Also experimental animal studies have shown that oral inoculation by periodontal pathogens results in accelerated atherosclerosis, and that bacterial DNA from the infecting pathogens can be localized within the vessel walls.

What is Atherosclerosis?
Cardiovascular disease (CVD), also called heart disease, is caused by disorders of the heart and blood vessels. It includes coronary heart disease (CHD), cerebrovascular disease, raised blood pressure, peripheral artery disease, rheumatic heart disease, congenital heart disease and heart failure. Many of these conditions are related to atherosclerosis.

Atherosclerosis is a condition that develops when a substance called plaque (atheroma) builds up in the walls of the arteries. It involves a gradual and focal accumulation of lipids, smooth muscle cells, white blood cells, cholesterol crystals, calcium, and fibrous connective tissue under the surface lining (endothelium) of the artery, ultimately forming an elevated plaque that protrudes into the vessel's lumen and significantly reducing blood flow. It is analogous to a kitchen drain pipe becoming gradually plugged with cooking grease and sludge.

How does atherosclerosis start?
The etiogenesis is not clear, but the popular belief is that it starts when the innermost layer of the artery known as endothelium becomes damaged. The arterial wall damage can be due to elevated levels of cholesterol and triglyceride in the blood, high blood pressure or cigarette smoke. Fats, cholesterol, platelets, cellular debris and calcium are deposited in the damaged artery wall overtime. These substances may stimulate the cells of the artery wall to produce still other substances resulting in more cells accumulating in the innermost layer of the artery wall where the atherosclerotic lesions form. At the same time, fat builds up within and around these cells. The innermost layer of the artery becomes markedly thickened by these accumulations, resulting in less blood supply to the heart, brain or limbs. Plaque may partially or totally block the blood's flow through an artery. The whole artery may be blocked when a piece of the plaque breaks off or when a blood clot (thrombus) forms on the plaque's surface. A heart attack or stroke can occur in such a sequelae

Possible explanations for the association between periodontal disease and atherosclerosis

1. It may merely reflect confounding by common risk factors that cause both periodontal disease and atherosclerosis, such as smoking, obesity, and diabetes.

2. The autoimmune theory, according to which antibodies against bacterial antigens may also react against endothelial protein, causing destruction of the artery wall and initiating the arterial lesion

3. Both atherosclerosis and periodontitis are inflammatory processes. The presence of gum inflammation enhances theory is supported by an increase in white blood cells, C-reactive protein and other markers for inflammation in patients with periodontitis.

4. Periodontal bacteria entering the bloodstream during chewing, or small cuts and tears made by dental procedures. Once in the bloodstream, bacteria can produce an enzyme that causes blood platelets to become sticky and form small blood clots which may contribute to the development of atherosclerosis.

What is the strength of the association between periodontitis and atherosclerotic heart disease?
The connection is indeed biologically plausible. Various epidemiological studies were published regarding this association in the past 20 years. A prospective cohort study of 9760 subjects published in British Medical Journal demonstrated a 25% increase in the risk for CHD associated with periodontal disease. A longer follow-up period demonstrated a stronger relationship, and the risk for CHD increased gradually with the severity of periodontal disease, suggesting a possible continuum between the degree of poor oral health and the risk for CVD. The American Academy of Periodontology reported that periodontitis patients have nearly twice the risk of having a fatal heart attack than patients with healthy gums. It is important to note that periodontitis and atherosclerosis share a number of powerful risk factors like smoking, diabetes mellitus, and low socioeconomic status, all of which can contribute to a confounded association. For this reason, epidemiologic studies of higher quality have statistically adjusted many of these confounding factors and found an independent association between periodontitis and atherosclerosis. Recent studies have demonstrated a positive relationship between periodontitis and CVD among people who never smoked. After evaluating the totality of the epidemiologic evidence, the American Heart Association made a statement which acknowledge the association between the two conditions independent of known confounders.

No causal relationship accepted as yet
While many acknowledge that periodontal infections are more frequent in patients with CVD, few are skeptical about a causal relationship between the two conditions. Richard Shannon (Allegheny General Hospital, Pittsburgh, PA) suggested that the bacterial DNA detected in the plaque could have just been left there by inflammatory cells. Shannon explained, “Inflammatory cells respond to plaque, but if they have previously been mopping up bacteria somewhere else in the body they could deposit those bacteria in the plaque when they reach it. The bacteria could then form what is known as a biofilm—they just sit there but do not actively replicate or cause infection”. Shannon pointed out that most people without CHD would still have some early atherosclerosis, but no bacteria in the arteries of control subjects who did not have CHD, suggesting that bacteria are not necessary to start the atherosclerotic process.

Does successful treatment of periodontitis will prevent the onset of cardiovascular disease or slow its progression?
Unfortunately, there is no direct peer-reviewed evidence to suggest that treating or preventing periodontal infections lead to fewer clinical cardiovascular events. The main reason for this knowledge gap is that researches that could answer these questions have not been conducted yet. To answer this question, definitive clinical trials to define the optimal timing of treatment, type of treatment procedures, maintenance protocol, length of follow-up, and the relationship of treatment result to the overall risk profile for CVD or certain groups of population is necessary. Hence, the research needs are formidable in size and duration, and so we may be years away from getting the definite answers. Very recently, findings from an observational study involving data from a US health insurance registry suggested that regular tooth scaling was associated with decreased risk of experiencing cardiovascular events during a seven-year period. Intervention studies have demonstrated that treatment of periodontitis results in improved function and thickness of artery wall, and general reduction in systemic inflammation which all contribute to a healthy heart.

So what messages can we communicate to the public given the available evidences as well as the current gaps in knowledge regarding this association? The observed association between periodontitis and atherosclerosis related heart disease is biologically plausible, the mechanisms mediating the link between the two conditions having been identified as well. Periodontal treatments do not typically include systemic pharmacotherapies and are associated with negligible adverse effects. Periodontal treatment results in improved function of blood vessel wall (endothelium) and reduced systemic inflammation which are important markers for cardiovascular health. Maintaining oral/periodontal health should be considered an integral part of a holistic approach to a healthy heart along with other health promoting behaviors – healthy diet, exercise, cessation of smoking. The dental team and the public can play an important role on this.