Teeth (singular, tooth) are structures found in the jaws of many vertebrates that are used to tear, scrape, and chew food. Some animals, particularly carnivores, also use teeth for hunting or defense. The roots of teeth are covered by gums.Teeth are among the most distinctive (and long-lasting) features of mammal species. Paleontologists use teeth to identify fossil species and determine their relationships. The shape of an animal's teeth is related to its diet. For example, plant matter is hard to digest, so herbivores have many molars for chewing. Carnivores, on the other hand, need canines to kill and tear meat.Humans are diphyodont, meaning that they develop two sets of teeth. The first set (the "baby," "milk," "primary" or "deciduous" set) normally starts to appear at about six months of age, although some babies are born with one or more visible teeth, known as neonatal teeth. Normal tooth eruption at about six months is known as teething and can be quite painful for an infant.Some animals develop only one set of teeth (monophyodont) while others develop many sets (polyphyodont). Sharks, for example, grow a new set of teeth every two weeks to replace worn teeth. Rodent incisors grow and wear away continually through gnawing, maintaining relatively constant length. Some rodent species, such as the sibling vole and the guinea pig, have continuously growing molars in addition to incisors

Dental anatomy is a field of anatomy dedicated to the study of tooth structures. The development, appearance, and classification of teeth fall within its purview, though dental occlusion, or contact among teeth, does not. Dental anatomy is also a taxonomical science as it is concerned with the naming of teeth and their structures. This information serves a practical purpose for dentists, enabling them to easily identify teeth and structures during treatment.The anatomic crown of a tooth is the area covered in enamel above the cementoenamel junction.The majority of the crown is composed of dentin with the pulp chamber in the center.The crown is within bone before eruption. After eruption, it is almost always visible. The anatomic root is found below the cementoenamel junction and is covered with cementum. As with the crown, dentin composes most of the root, which normally have pulp canals. A tooth may have multiple roots or just one root. Canines and most premolars, except for maxillary (upper) first premolars, usually have one root. Maxillary first premolars and mandibular molars usually have two roots. Maxillary molars usually have three roots. Additional roots are referred to as supernumerary roots.

Humans usually have 20 primary teeth (also called deciduous, baby, or milk teeth) and 32 permanent teeth. Among primary teeth, 10 are found in the maxilla and the other 10 in the mandible Teeth are classified as incisors, canines, and molars. In the primary set of teeth, there are two types of incisors, centrals and laterals, and two types of molars, first and second. All primary teeth are replaced with permanent counterparts except for molars, which are replaced by permanent premolars. Among permanent teeth, 16 are found in the maxilla with the other 16 in the mandible. The maxillary teeth are the maxillary central incisor, maxillary lateral incisor, maxillary canine, maxillary first premolar, maxillary second premolar, maxillary first molar, maxillary second molar, and maxillary third molar. The mandibular teeth are the mandibular central incisor mandibular lateral incisor, mandibular canine, mandibular first premolar, mandibular second premolar, mandibular first molar, mandibularsecond molar, and mandibular third molar. Third molars are commonly called "wisdom teeth" and may never erupt into the mouth or form at all. If any additional teeth form, for example, fourth and fifth molars, which are rare, they are referred to as supernumerary teeth.

Most teeth have identifiable features that distinguish them from others. There are several different notation systems to refer to a specific tooth. The three most commons systems are the FDI World Dental Federation notation, the universal numbering system, and Palmer notation method. The FDI system is used worldwide, and the universal is used widely in the United States.Oral hygiene is the practice of keeping the mouth clean and is a means of preventing dental caries, gingivitis, periodontal disease, bad breath, and other dental disorders. It consists of both professional and personal care. Regular cleanings, usually done by dentists and dental hygienists, remove tartar (mineralized plaque) that may develop even with careful brushing and flossing. Professional cleaning includes tooth scaling, using various instruments or devices to loosen and remove deposits from teeth.The purpose of cleaning teeth is to remove plaque, which consists mostly of bacteria. Healthcare professionals recommend regular brushing twice a day (in the morning and in the evening, or after meals) in order to prevent formation of plaque and tartar. A toothbrush is able to remove most plaque, excepting areas between teeth. As a result, flossing is also considered a necessity to maintain oral hygiene. When used correctly, dental floss removes plaque from between teeth and at the gum line, where periodontal disease often begins and could develop caries. Electric toothbrushes not considered more effective than manual brushes for most people.The most important advantage of electric toothbrushes is their ability to aid people with dexterity difficulties, such as those associated with rheumatoid arthritis.In addition, fluoride therapy is often recommended to protect against dental caries. Water fluoridation and fluoride supplements decrease the incidence of dental caries. Fluoride helps prevent dental decay by binding to the hydroxyapatite crystals in enamel.The incorporated fluoride makes enamel more resistant to demineralization and thus more resistant to decay. Topical fluoride, such as a fluoride toothpaste or mouthwash, is also recommended to protect teeth surfaces. Many dentists include application of topical fluoride solutions as part of routine cleanings.