The teeth (latin: dentes) are small solid bone-like structures that fit into the jaws and form the upper maxillary and lower mandibular rows. The teeth are mainly responsible for the mechanical processing of food. An adult has a total of 32 permanent teeth.
Humans are provided with two sets of teeth. The first set are the deciduous or the milk teeth, and the second are the permanent teeth. The milk teeth are 20 in number and appear during childhood at the age of six to eight months and are replaced by the permanent teeth at 6 to 12 years of age. The permanent teeth replace the milk teeth, and the last to appear are the molar teeth, also known as the wisdom teeth, which emerge at the age of 17 to 24 years.
Each tooth has three main parts: the root, the neck and the crown. The rooth is the part of the tooth lying in the dental alveoli of the alveolar arches of the upper and lower jaws. The neck of the tooth is a slightly narrowed part between the root and the crown, and it is covered by gums. The crown is the portion of the tooth which is elevated above the gums and visible in the mouth. The surface of the crown is responsible for the mechanical processing of food.
Each tooth is fixated within the alveolus of the maxilla or mandible with the help of the periodontium, specialized fibrous tissue between the root of the tooth and the bone.
The teeth are classified according to the number of roots and the shape of the crown. There are four types of human teeth:
The incisor teeth (also known as incisors, latin: dentes incisivi) have a crown shaped cutting chisel with a triangular lateral surface. Humans are provided by eight incisor teeth: four in the upper and four in the lower jaw. The incisor teeth have a long single conical root and they are for biting, cutting the food.
The canine teeth (latin: dentes canini) in human oral anatomy are also known as cuspids or eye teeth. There are two canine teeth in the upper and two in the lower jaw, each separated by four incisors. Canine teeth have very deep and long single roots, flattened and grooved on the sides. The crown of the canine teeth have a sharpened conical form with spear-like cutting edges. They are for gripping and tearing the food.
The premolar teeth (also known as bicuspids, premolars, latin: dentes premolares) are located between the canine and molar teeth. The premolar teeth have a single root, which is usually bifurcated, and the crown of these teeth has a cuboid shape. There is a total of eight premolars in the human oral cavity: four in the upper and four in the lower jaw (two on each side). The premolar teeth provide chewing or crushing of food.
The molar teeth (also known as molars, latin: dentes molares) are located in the back of the oral cavity. Adults have a set of twelve molar teeth: three on each side in the upper and lower jaws. The molars have a crown with a cuboid-shaped convex on the buccal and lingual surfaces and flattened on its contact surfaces. The chewing surface of each molar tooth is square with three or more cusps. The upper molar teeth have three roots, but the lower have two roots. The molar teeth provide the grinding of food.
The teeth are innervated by the maxillary and mandibular branches of the trigeminal nerve (CN V).
The upper or maxillary teeth are supplied the following nerves that originate from the maxillaryn nerve (CN V2):
- anterior superior alveolar nerve,
- middle superior alveolar nerve,
- posterior superior alveolar nerve.
The lower or mandibular teeth are innervated by the following nerves originating from the mandibular nerve (CN V3):
- incisive nerve,
- inferior alveolar nerves.