SS2 Biology Lesson Note on Mammalian Teeth

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MAMMALIAN TEETH

The type of teeth possessed by a mammal is related to the type of food it eats. The number, arrangement and conformation of teeth in an organism are referred to as its dentition. When all the teeth are the same shape and size as in fishes, amphibians and reptiles it is called homodont dentition. When they differ in shape as in dogs, man and rabbits it is heterodont dentition.

Mammals usually have four different types of teeth namely the incisors, canines, premolars and molars. Man has two sets of teeth during his lifetime; the milk teeth when young and the permanent teeth when mature. There are 20 milk teeth and 32 permanent teeth.

Types of Teeth

1. Incisors – These are flattened, chisel-like with a sharp edge for cutting and holding onto the food/prey. They are located in the front of the jaw.
2. Canines – These have sharp, pointed tips and are used for tearing flesh. They are next to the incisors.
3. Premolars – These have broad ridged surfaces called cusps. They are used for grinding and chewing food. They are located towards the back of the jaw.
4. Molars – These also have broad, ridged surfaces and are used for chewing and grinding food. They are found at the extreme back of the jaws.

Dental Formula

This refers to the number, type and arrangement of teeth in one half of each jaw.

Example in;

• Man; I 2/2 ; C 1/1 ; PM 2/2 ; M 3/3
• Dog; I 3/3 ; C I/I ; PM 4/4 ; M 2/3
• Rabbit; I 2/1 ; C 0/0 ; PM 3/2 ; M 3/3

Structure of a Tooth

A typical tooth has three parts; the crown, the neck and the root. The crown is the part above the gum. The root is embedded in the jaw and the neck is the part on the same level with the gum, it is the narrow junction between the crown and root.

The incisors and canines have one root each while the premolars and molars have two or three roots each.

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