TEETH

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TEETH
Teeth are hard conical structures set in the alveoli of the upper and lower jaws that are used in mastication and in assisting in articulation. They are the hardest and most characteristically stable tissue in the body. Each individual has 2 sets of teeth (dentitions).  A tooth is identified and described on the basis of whether it is deciduous (primary) or permanent (secondary) teeth.
1. Decidious or temporary teeth:- are usually immature and are present in children. They are usually 20 in numbers (i.e 2 incisors, 1 canine and 2 molar in each half of the jaw). Before eruption, the developing teeth reside in the alveolar arches as tooth buds. 
Deciduous teeth begin to erupt after 6 months of birth (starting from lower central incisors) and are all present after 24months.
2. Permanent teeth replace the deciduous teeth starting from the 6th year after birth to 25th year when the whole teeth are expected to have been completed (32 teeth).
 


CLASSIFICATION
Teeth can be classified according to their shape and functions.
1. Incisors:- they are chisel– shaped and are for cutting of food.
2. Canines:- they are conical in shape, for piercing and tearing
3. Premolars (bicuspids):- have broad crowns with rounded cusps, for grinding and crushing of food.
4. Molars (4 cusps):- they have square crowns, for grinding of food.

DENTAL FORMULA
This is a graphical representation of the types, numbers and position of teeth in the oral cavity.
Decidous dentition:- I =2/2, C =1/1, M =2/2 =(10 *2)=20 teeth.
Permanent dentition:- I =2/2, C =1/1, PM =2/2, M =3/3 =(16*2)=32.

Parts and Structure of the Teeth
A tooth has a crown, neck, and root. The crown projects from the gingiva. The neck is between the crown and the root. The root is fixed in the tooth socket (dental alveoli) by the periodontium in the alveolar processes of the mandible and maxillae; the number of roots varies. Most of the tooth is composed of dentin, which is covered by enamel over the crown and cement over the root.  Enamel is composed primarily of calcium phosphate and is the hardest substance in the body.
 The central region of the tooth contains the pulp cavity. The pulp cavity contains the pulp, which is composed of connective tissue with blood vessels, lymph vessels, and nerves. A root canal, continuous with the pulp cavity, opens to the connective tissue surrounding the root through an apical foramen. The tooth receives nourishment through vessels traversing the apical foramen.

 

BLOOD SUPPLY
The teeth receive blood supply from superior and inferior alveolar arteries which are branches of maxillary artery. They are drained by the alveolar veins.
Nerve supply
Teeth are innervated by alveolar branch of mandibular and maxillary nerves.

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