Plaque refers to a buildup of unwanted material on a surface in the body. The term most commonly describes three things: the sticky film of bacteria on your teeth, the fatty deposits inside your arteries, and the protein clumps found in the brains of people with Alzheimer’s disease. Each type forms differently, causes different problems, and requires a different approach to manage.
Dental Plaque: The Sticky Film on Your Teeth
Dental plaque is a yellowish, sticky biofilm that forms on the surface of your teeth. It’s made up of bacteria embedded in a matrix of proteins and sugars, some produced by the bacteria themselves and some from your saliva. That “fuzzy” feeling on your teeth when you haven’t brushed in a while is plaque you can feel.
Over 600 bacterial species have been identified in dental plaque, and roughly half of those can’t even be grown in a lab yet. When you eat sugary or starchy foods, these bacteria feed on the sugars and produce acid as a byproduct. That acid starts dissolving tooth enamel once the pH at the tooth surface drops to around 5.5, which can happen within minutes of eating. Over time, this acid exposure leads to cavities. Certain acid-producing bacteria are especially associated with tooth decay, but even common, everyday mouth bacteria can generate enough acid to damage enamel if sugar is present frequently.
Plaque also causes gum disease. When it accumulates along and below the gumline, it triggers inflammation that can progress from mild gingivitis to severe periodontal disease. Severe periodontal disease affects roughly 1 billion people worldwide.
Plaque vs. Tartar
You can remove dental plaque yourself with regular brushing and flossing. If you don’t, it hardens into tartar (also called calculus) within days. Tartar is made mostly of dead bacteria that have mineralized, mixed with proteins from your saliva. Its primary mineral component is calcium phosphate. Once plaque has calcified into tartar, no amount of brushing will get it off. Only a dentist or dental hygienist can remove it with professional tools during a cleaning.
Arterial Plaque: Buildup Inside Blood Vessels
Arterial plaque is something entirely different. It forms inside the walls of your arteries and is the hallmark of atherosclerosis, the disease behind most heart attacks and strokes. This type of plaque is a mixture of fat, fibrous tissue, calcium deposits, smooth muscle cells, and immune cells. Over years or decades, these materials accumulate in the artery wall, thickening it and gradually narrowing the channel blood flows through.
The process starts when the inner lining of an artery gets damaged, often by high blood pressure, smoking, or high cholesterol. Fatty substances in the blood seep into the damaged area, and immune cells rush in to clean up. Instead of resolving, the inflammation becomes chronic. Smooth muscle cells migrate into the area, and the whole mass slowly grows into a plaque that bulges into the artery.
Stable vs. Vulnerable Plaque
Not all arterial plaques are equally dangerous. A stable plaque has a thick cap of fibrous tissue holding it together. It may narrow the artery and cause symptoms like chest pain during exercise, but it’s less likely to cause a sudden heart attack. A vulnerable plaque, on the other hand, has three key features identified in autopsy studies: a thin fibrous cap (less than 65 micrometers thick), a large pool of fatty, dead-cell debris underneath, and active immune cells clustered near the cap’s surface.
When a vulnerable plaque ruptures, its contents spill into the bloodstream. The body treats this like an injury and activates clotting. A blood clot can form rapidly at the rupture site, abruptly blocking the artery. If that artery feeds the heart, the result is a heart attack. If it feeds the brain, it’s a stroke. This is why someone with no prior symptoms can have a sudden cardiac event: the plaque that ruptures may not have been large enough to cause noticeable narrowing beforehand.
Can Arterial Plaque Be Reversed?
Clinical trials have shown that lifestyle changes can shrink atherosclerotic plaques and stabilize them so they’re less likely to rupture. The key interventions are diet improvements (particularly reducing saturated fat), smoking cessation, regular exercise, and stress management. Cholesterol-lowering medications also have strong evidence for reducing plaque size and stabilizing vulnerable plaques. The Lifestyle Heart Trial, one of the earliest randomized controlled studies on this question, demonstrated that comprehensive lifestyle changes could affect coronary atherosclerosis within one year. Multiple trials since then have confirmed these findings, and a meta-analysis of diet and exercise interventions found they effectively decrease plaque burden in both coronary and carotid arteries.
Brain Plaque: Amyloid in Alzheimer’s Disease
The third type of plaque that comes up in medicine is the amyloid plaque found in the brains of people with Alzheimer’s disease. These plaques are clumps of a small protein fragment called beta-amyloid that accumulate outside brain cells. Along with tangled fibers of another protein (tau) found inside neurons, amyloid plaques are the two defining features required for an Alzheimer’s diagnosis.
Beta-amyloid is a fragment cut from a larger protein that sits in brain cell membranes. In a healthy brain, these fragments are produced and cleared away routinely. In Alzheimer’s, the fragments misfold, stick together, and form insoluble clumps that the brain can’t remove. These clumps first appear as small, soluble clusters of just a few molecules. Even at that tiny scale, they’re toxic. Clusters as small as two molecules, isolated from Alzheimer’s patients, have been shown to disrupt the electrical signaling between brain cells. Larger soluble clusters poison neurons and interfere with the brain’s ability to strengthen connections between cells, a process essential for forming new memories.
One puzzling aspect of amyloid plaques is that the amount of plaque in the brain doesn’t closely match how severe someone’s symptoms are. Some people accumulate significant plaque deposits but show only mild cognitive decline, while others deteriorate rapidly with less visible plaque. This suggests the large, visible plaques may be less harmful than the smaller, soluble clusters circulating between cells. The relationship between amyloid buildup and cognitive loss remains one of the central questions in Alzheimer’s research, and it has shaped the debate around newer treatments designed to clear amyloid from the brain.
Why the Same Word Means Different Things
The word “plaque” comes from a French term meaning a flat plate or patch. In medicine, it broadly describes any abnormal deposit that forms on or within a body structure. Dental plaque is a living bacterial community on the tooth surface. Arterial plaque is a slow-growing mass of fat, calcium, and cells inside artery walls. Brain plaque is a clump of misfolded protein fragments between neurons. They share a name because they’re all unwanted accumulations, but their causes, compositions, and consequences are fundamentally different.