dentitions

Dentitions refers to the arrangement, types, and condition of teeth within the jaws of a species. In humans, dentition is typically heterodont and diphyodont, meaning there are different tooth types and two successive sets of teeth: deciduous (primary) and permanent (secondary).

The deciduous dentition consists of 20 teeth, arranged per quadrant as 2 incisors, 1 canine, and 2 molars (2-1-0-2). The permanent dentition contains 32 teeth, arranged per quadrant as 2 incisors, 1 canine, 2 premolars, and 3 molars (2-1-2-3). The teeth are located in the maxillary (upper) and mandibular (lower) dental arches and work together in occlusion. The main tooth types are incisors (cutting), canines (tearing), premolars (transitional/for grinding), and molars (grinding). Teeth comprise enamel, dentin, cementum, and dental pulp, anchored in the jawbone by the periodontal ligament.

Development and eruption follow a characteristic timeline. Odontogenesis begins before birth, deciduous teeth usually erupt from about 6 months to 2-3 years, and begin to shed around age 6 as permanent teeth emerge through adolescence and into early adulthood. Third molars, or wisdom teeth, may erupt last or be absent.

Variations in dentitions include agenesis (missing teeth), supernumerary teeth, and ectopic eruption. In addition to humans, dentition styles vary across species; many animals are monophyodont or polyphyodont, and some are homodont rather than heterodont.

The dentition plays a critical role in nutrition, speech, and aesthetics, and is subject to diseases such as dental caries and periodontal disease. Preventive care includes oral hygiene, fluoride use, sealants, and regular professional check-ups.