Teeth can be affected by a variety of diseases as well as by developmental malformations. The common diseases of human dentition are dental caries, periodontal disease, and malocclusion.
Dental caries is a bacterially caused resorption or destruction of the enamel and dentin of the tooth, leading eventually, if untreated, to an infection of the dental pulp and an abscess of the apex of the tooth. The caries-causing bacteria proliferate within a protective covering, called plaque, on the tooth surfaces and produce both acid and enzymes to break down the calcified substances of the tooth. Sweets and other foods that stick to the tooth surface increase the activity of the caries-producing bacteria. Saliva, containing immunoglobulins and other antibacterial substances, tends to protect against caries, and decreased flow of saliva usually results in increased caries. Tooth shape and hereditary factors determine a person's susceptibility to the disease.
Periodontal disease is a chronic or low-grade infection of the tissues supporting the tooth and can result in tooth loss by recession or loss of the supporting tissues. Malocclusion, or significant inability to close the teeth properly because of abnormal alignment, results in difficulty in chewing and can eventually lead to increased caries and periodontal disease risk. Caries and periodontal disease can be prevented by proper oral hygiene measures to remove bacterial plaque from the surfaces of teeth, and caries can be prevented by public health measures such as addition of fluoride to drinking water.
Dental diseases also occur in animals, and many species are used for studies in the experimental pathology of caries and periodontal disease.
Because of their high degree of calcification, teeth have been well preserved over thousands of years, and they have been used extensively in studies on the evolution of humans from hominidlike primat