Encrustations formed from microbes (bacteria, algae, fungi, plankton, or protozoa) embedded in an EXTRACELLULAR POLYMERIC SUBSTANCE MATRIX that is secreted by the microbes. They occur on body surfaces such as teeth (DENTAL DEPOSITS); inanimate objects, and bodies of water. Biofilms are prevented from forming by treating surfaces with DENTIFRICES; DISINFECTANTS; ANTI-INFECTIVE AGENTS; and anti-fouling agents.