An alloy of mercury. Practically all metals will form alloys, or amalgams, with mercury, with the notable exception of iron. Amalgams are used as dental materials (see illustration), in the concentration of gold and silver from their ores, and as electrodes in various industrial and laboratory electrolytic processes. However, dental amalgam have been largely replaced by resin-based composite materials.

The scientific study of people, with their living and extinct primate relatives, using the evidence of teeth. Dental anthropologists include not only those trained in anthropology but also practicing dentists, anatomists, radiologists, forensic scientists, biochemists, geneticists, archeologists, paleontologists and zoologists.

A disease in which the mineralized tissues of the tooth undergo progressive destruction from the outside surface of the tooth. The scientific term of dental caries (Fig. 1) is more commonly referred to as tooth decay or cavities. Carious lesions occur when bacteria colonize the tooth surface and, under certain conditions, produce sufficient acids to demineralize the enamel covering of the tooth crown or the cementum covering the root, and then the underlying dentin. As the destruction of the dentin progresses, along with breakdown of the organic components, the bacteria invade the dead tissue and enter the pulp chamber. The pulpal tissue becomes infected, and the typical toothache may ensue. Ultimately, the infection can destroy the pulpal tissue and extend out through the apical openings of the roots and into the surrounding periodontal tissues. With proper oral hygiene, including the use of fluoride, dental caries can be largely prevented. See also: Bacteria; Dentistry; Fluorine; Medical bacteriology; Microbiology; Mouth disorders; Periodontal disease; Tooth; Tooth disorders

The branch of biomedical science concerned with the embryology, development, and structure of the teeth, jaws, oral cavity, and adjacent structures, and with the prevention, diagnosis, and treatment of their abnormalities. The practice of general dentistry requires a thorough knowledge of not only the structure, growth, function, and pathologic conditions of the oral cavity and related structures, but also the relationship of the oral cavity to other parts of the body in health and disease, and a recognition of oral manifestations of various systemic diseases. Nevertheless, most of the dentist's time and effort are devoted to the treatment of dental caries (decay) and periodontal diseases (see illustration). In countries with professional and affordable dental care, the prevalence of dental caries, especially in children and young adults, has decreased rapidly; a similar trend is occurring with gingivitis (inflammation of the mucous membrane surrounding the tooth sockets) and periodontitis (inflammation of the tissues surrounding the teeth). As a consequence, other conditions are becoming relatively more important in general dentistry. These include orofacial and temporomandibular joint pain; oral mucosal lesions associated with immunosuppression, irradiation, and chemotherapy in patients with cancer or organ transplants; and unusual mucosal and periodontal lesions in patients with acquired immune deficiency syndrome (AIDS). See also: Acquired immune deficiency syndrome (AIDS); Chemotherapy and other antineoplastic drug treatments; Dental caries; Immunosuppression; Mouth disorders; Pathology; Tooth; Tooth disorders

The arrangement, type and number of teeth which are variously located in the oral or the pharyngeal cavities, or in both. Teeth are found in areas where there is an underlying supporting structure of cartilage or bone and where stomodeal ectoderm is present. The bones with which these structures are usually associated are the mandible (both the cartilaginous bones and the dentary), the premaxillaries and the maxillaries. However, in certain vertebrates, the vomerine, palatine, parasphenoid and pterygoid bones may be involved; and in many fishes, teeth are also found on the branchial arches.

The use of dental knowledge in the judicial process. Forensic dentistry, or forensic odontology, is best known for its usefulness in linking an identifying name to unknown human remains (Fig. 1). This may be accomplished in single instances, such as when a body is discovered along a lake or river shore, with the person having presumably drowned. Alternatively, more than one victim may be involved, such as in a house fire or an automobile accident. In some cases, referred to as multiple-fatality incidents (or mass fatalities or disaster victim identification), large numbers of deceased individuals may require identification. Recent examples include Hurricane Katrina in 2005, the Sumatra–Andaman earthquake and tsunami in 2004, the World Trade Center attack in 2001, and any of a number of common carrier incidents, including the 2009 crash of Continental Connection Flight 3704 in Buffalo, New York. Forensic dentists also assist in law enforcement cases involving suspected biting activity (animal or human) and in abuse cases involving head and neck injury. In addition, many forensic dentists act as expert witnesses in litigation involving professional liability claims against dentists and in personal injury cases involving the jaws or other oral structures.

The oral or buccal cavity and its related structures. The mouth (see illustration) is a key anatomical structure as it is the orifice through which food and air enter the body of most animals. Also termed the oral or buccal cavity, the mouth forms in the embryo from an in-pocketing of the skin—namely, the stomodeum; thus, it is lined by ectoderm and is not, properly speaking, part of the digestive tract. Functionally, however, the mouth forms the first portion of both the digestive and respiratory systems. In particular, various special structures are found in, or associated with, the mouths of most vertebrates. In terms of disease, the mouth is subject to numerous pathologies potentially affecting the lips, tongue, teeth, gums, and related structures. See also: Animal; Digestive system; Mouth disorders; Respiratory system; Vertebrata

Pathologies of form and function that affect the oral cavity and its related structures. The mouth, or oral (buccal) cavity, which comprises the lips, tongue, teeth, gums, and related structures, is subject to a large number of disease processes. Periodontitis (an inflammatory disease of the tissues supporting and surrounding the teeth; see illustration) and dental decay (dental caries) are the most common diseases; together, they account for almost all tooth loss. Other diseases of the mouth can be classified as cysts; neoplasms; diseases of the salivary glands; keratoses, inflammatory, ulcerative, and proliferative lesions; oral infections; and an unusual form of rapidly destructive periodontitis observed in some patients with acquired immune deficiency syndrome (AIDS). See also: Acquired immune deficiency syndrome (AIDS); Dental caries; Dentistry; Mouth; Periodontal disease; Tongue; Tooth; Tooth disorders

An inflammatory lesioned condition caused by bacteria affecting the tissues housing the roots of the teeth. Periodontal disease, sometimes called gum disease or pyorrhea, occurs when the tissues surrounding the teeth become pathologically inflamed by bacteria. In general, periodontal disease increases in prevalence and severity with advancing age, and it is a principal cause of tooth loss in adult humans throughout the world. When only the gum tissue or gingiva is affected, the disease is called gingivitis; however, when the inflammatory processes extend into deeper structures, it is known as periodontitis (Fig. 1). The diseased tissues appear abnormally red and slightly swollen, and they tend to bleed (sometimes profusely) when the teeth are brushed. In some cases, the gums may become thickened and scarred, and they may recede, exposing the root surfaces. As the disease advances, the attachment of the gum to the tooth is lost, creating a periodontal pocket; subsequently, a large portion of the gum tissue is destroyed, and the bone surrounding the roots is resorbed. The teeth become loose, abscesses form, and extraction is required. See also: Bacteria; Bacteriology; Dentistry; Inflammation; Medical bacteriology; Microbiology; Mouth disorders; Tooth; Tooth disorders

An organ located at the base of the oral cavity and found in all vertebrate animals. It is best developed in terrestrial vertebrates, where it takes on the functions of food procurement, food transport, and acquisition of chemosensory signals. The tongue generally is not a significant independent organ in fish, and it is secondarily reduced in organisms that feed aquatically, such as crocodilians and some turtles.