Dental tartar, plaque and gum disease. Close-up of the teeth of a patient with dental plaque and tartar, that has caused gum disease (gingivitis). Plaque consists of a film of bacteria embedded in a glycoprotein matrix. The matrix is formed from bacterial secretions and saliva. Plaque is the main cause of tooth decay. The bacteria feed on sugars in food, producing acid as a waste product. This acid corrodes the teeth's enamel coating, resulting in dental caries. A build-up of dental plaque can also lead to inflamed and infected gums (as here). Tartar, or calculus, is a form of hardened dental plaque produced by the continual accumulation of salivary minerals on existing plaque.