The most common dental diseases, tooth decay and gum ailments, result from the longstanding biofilm on tooth surfaces. A tenacious layer, known as the pellicle, is always present on the teeth. The pellicle adheres strongly to germs in the mouth, forming a microbial community referred to as dental plaque. Many people mistakenly identify the soft, non-mineralized, whitish deposit found around the gingival margins, often associated with poor oral hygiene, as dental plaque. However, this substance is materia alba, not plaque. Materia alba consists of food debris, microorganisms, and dead cells.

The key difference between plaque and materia alba is that plaque is invisible and cannot be removed by simply rinsing the mouth—it requires brushing and flossing. In contrast, materia alba is visible and can be washed away with mouth rinsing. Dental plaque can be made visible by using plaque-disclosing tablets, which stain the invisible plaque a pink color.