Dental plaque/biofilm is a soft mass of bacterial colonies made up of normal oral flora. Diet and retentive areas contribute to adherence of this biofilm to the tooth surfaces. Plaque/biofilm contributes, along with fermentable carbohydrate ingestion, to formation of dental caries. Plaque/biofilm can be both supragingival (above the gumline) and subgingival (below the gumline). Both need to be removed on a daily basis in order to avoid dental diseases.
Beverly to Mr. Smith: "Mr. Smith, I want to talk to you about your oral hygiene. Even though your gums look healthy there appears to be some plaque in a few areas of your mouth that became evident when I used the disclosing tablets. These tablets stain the plaque red to make it easier to see. Let me give you this mirror and show you those areas so you can pay particular attention to those areas when you brush and floss your teeth."