The biofilm that builds up on the teeth is called plaque, more specifically dental plaque. It is a sticky microbial community made up mostly of bacteria, along with other microorganisms, embedded in a protective matrix.
Plaque begins forming soon after teeth are cleaned. Saliva creates a thin protein-rich coating called the acquired pellicle on the enamel, allowing early bacterial colonizers to attach. As the bacteria multiply, they organize into microcolonies and produce substances that help the biofilm adhere to the tooth surface.
Plaque is not the same as tartar, or dental calculus. Tartar forms when plaque mineralizes and hardens, and it generally cannot be removed completely with ordinary brushing. If plaque remains undisturbed, its acids can contribute to tooth decay, while bacteria near or below the gumline can contribute to gingivitis and periodontal disease.
Regular brushing, cleaning between the teeth, and professional dental care help control plaque. Dental-disclosing tablets can temporarily stain plaque, making missed areas easier to see.