Types of dentitions and teeth
In dentitions that are only shed and replaced once (diphyodontia), the rather smaller teeth of the first dentition are replaced by the larger teeth of the second dentition. In humans, the primary dentition appears first with 20 teeth (dentes decidui). It is replaced and supplemented by the complete, secondary dentition of 32 permanent teeth (dentes permanentes). The primary dentition is also known as the temporary dentition.
The teeth in the primary and permanent dentitions are arranged in superior and inferior dental arches (arcus dentalis superior and inferior). In mammals, and hence in humans, the dentition is heterodont (different kinds of teeth), and the teeth can be divided into the following functional groups (Fig 1-15).
- Anterior teeth (dentes anteriores):
- Incisors (dentes incisivi; dens incisivus; incidire = to cut; pre-canine teeth = teeth in front of the canines)
- Canines (dentes canini; dens caninus; dens an-gularis; angulus = corner, angle)
- Posterior teeth (dentes posteriors):
- Premolars (dentes praemolares; dens prae-molaris; dens bicuspidatus = two-cusp or two-point teeth; cuspis = point; dens buccalis mi-noris = small back tooth)
- Molars (dentes molares; dens molaris; dens multicuspidatus = multi-point teeth; dentes buccales majores = large back teeth)
The dentition is symmetric in both dental arches: The maxilla and mandible each contain the same number of teeth and groups of teeth, and they show mirror symmetry. Each half of either jaw contains a quarter of all the teeth: two incisors, one canine, two premolars, and three molars. The third (last) molar is often called the wisdom tooth (dens serotinus).
The permanent dentition contains:
- 12 anterior teeth (8 incisors, 4 canines)
- 20 posterior teeth (8 premolars, 12 molars)
The primary dentition contains:
- 12 anterior teeth (8 incisors, 4 canines)
- 8 posterior teeth (all molars)
The primary dentition has no premolars and only two so-called primary molars in each half of each arch.