The teeth are one of the constituents of the oral region. In adults, there are a total of 32 teeth divided equally between the upper and lower jaws. These teeth are attached to sockets (alveoli) in two elevated arches of bone: the mandible below, and the maxillae above. The main function of the teeth is to cut, reduce and mix food with saliva during mastication (chewing). They also have a role in articulation. Throughout a human's life span, two successive sets of teeth develop. They are the deciduous primary teeth (baby teeth) and the permanent secondary teeth (adult teeth). Children have about 20 deciduous teeth that emerge from the gingivae between six months and two years of age. Permanent teeth begin to replace them starting around the age of six years old, and can continue their emerging during adulthood.
Each tooth is made up of a crown, neck and root. The crown projects from the gingivae (gums), which are specialized areas of oral mucosa that surround the teeth and cover nearby areas of the alveolar bone. The neck extends between the crown and the root. The root is a structure that's firmly fixed in the tooth socket by firm connective tissue, the periodontium. Teeth are mostly composed of dentin, a calcified tissue that is covered by enamel over the crown and by cement over the root. The dental pulp cavity is present in the center of each tooth. It is made up of connective tissue, blood vessels and nerves. The root canal (pulp canal) transmits nerves and vessels to and from the pulp cavity.
On each side in both the maxillary and mandibular arches are two incisors, one canine, two premolars and three molar teeth. Each one of these teeth can be identified by their own unique characteristics. The incisor teeth are the 'front teeth'. They have one root and a chisel-shaped sharp crown designed for cutting. The canines lie posterior to the incisors and they are the longest teeth. They have a crown with a single prominent cusp that's made for grasping. The premolar teeth have two pointed cusps, one on the cheek side and the other on the tongue side, and generally a single root. The premolars are designed for the grinding of food. Finally, the molar teeth are present behind the premolars. They have crown with three to five cusps, and three roots. Molars are designed for food grinding as well.
Teeth are supplied by blood vessels that branch from the maxillary artery, whether directly or indirectly. The inferior alveolar artery supplies all the lower teeth, while the superior teeth are supplied by the anterior and posterior superior alveolar arteries. The venous drainage generally follows that of the arteries. All the nerves that innervate the teeth are branches of the trigeminal nerve (V). The lower teeth are innervated by the inferior alveolar nerve, a branch of the mandibular nerve (V3). The upper teeth, on the other hand, are innervated by the anterior, middle, and posterior superior alveolar nerves that originate from the maxillary nerve (V2).