The word “plaque” describes a sticky deposit of material that builds up on a surface, applying to two fundamentally different conditions in the human body: dental plaque and arterial plaque. Both formations represent a buildup of matter that can compromise health over time. This article focuses on the appearance and formation of these two types, which affect the oral cavity and the vascular system, respectively.
Appearance of Dental Plaque
Dental plaque is a colorless, sticky film that constantly forms on the teeth, making it initially difficult to see. This early stage is a microbial biofilm, a complex community of bacteria encased in a protective matrix of proteins, lipids, and polysaccharides. When the tongue runs over the teeth, this soft, unmineralized deposit often feels like a fuzzy or slippery coating. Plaque becomes visible only after it has accumulated and thickened, typically over one to two days without proper cleaning. At this point, the deposit takes on a yellowish-white, opaque appearance, often most noticeable near the gum line and between teeth.
If plaque is not removed, it begins to mineralize by absorbing calcium and phosphate salts from saliva. This process hardens the deposit into dental calculus, commonly known as tartar, which cannot be removed by simple brushing or flossing. Calculus presents as a hard, porous deposit, often yellow, brown, or even dark green or black, particularly when located below the gum line.
Appearance of Arterial Plaque
Arterial plaque, the hallmark of atherosclerosis, forms within the artery wall, not on the surface exposed to blood flow. This buildup begins as soft, fatty material consisting primarily of cholesterol, lipids, cellular debris, and inflammatory cells. Inside the artery wall, the lesion appears as a yellowish, soft mound covered by a fibrous cap.
The stability of the plaque dictates its appearance, distinguishing between soft and hard lesions. Soft, or “vulnerable,” plaque has a large, lipid-rich core and a thin, fragile fibrous cap. This type is prone to rupture, which exposes the underlying material to the bloodstream and triggers clot formation.
Conversely, “hard” plaque is more stable, containing higher amounts of calcium and dense fibrous tissue. As plaque ages, calcium deposits accumulate, giving the lesion a stiff, white, or chalky appearance.
How Plaque Develops
The formation of dental plaque begins almost immediately after teeth are cleaned, starting with a layer of salivary proteins called the acquired pellicle adhering to the tooth surface. Bacteria then attach to this thin protein film, colonizing the area and multiplying rapidly to form the sticky, organized biofilm. Over time, the bacteria produce an acidic byproduct that erodes tooth enamel. If left undisturbed, mineral components in saliva cause the plaque to harden into calculus.
The development of arterial plaque, a process called atherosclerosis, is initiated by damage to the endothelium, the inner lining of the artery. This damage, often caused by factors like high blood pressure or high cholesterol, allows low-density lipoprotein (LDL) cholesterol particles to infiltrate the artery wall. Immune cells known as macrophages enter the area to consume the trapped cholesterol, transforming into lipid-laden foam cells. These foam cells accumulate and multiply, forming the initial fatty streak that eventually matures into the complex lesion known as arterial plaque.