Five Types of Teeth in an Adult's Mouth

The human tooth is made out of four types of tissue. Pulp is the innermost layer, dentin protects it and makes up the largest part of the tooth, cementin surrounds and protects the root and enamel -- the hardest substance in the human body -- makes up the protective outermost layer of the tooth. The baby teeth begin to fall out when a person is about 6 years old, to be replaced by a set of 32 adult teeth.

Incisors

• The average adult human has eight incisors, or cutting teeth. They are located on the top and the bottom jaw, and are the teeth in the very front. They have somewhat flat surfaces and are made to slice and bite through food. They each have one long, conical root.

Canines

• The four canine teeth are located in the corners of the mouth, one on either side of the line of incisors on each jaw. Sometimes the canines on the upper jaw are referred to as "eyeteeth." They are longer than any other type of human tooth and distinguished by their long conical shape. They are made for tearing and shredding food.

Premolars

• The eight premolars are used to chew and grind food. They are found next to and behind the canine teeth on both jaws and are sometimes known as the "bicuspid teeth." They have a flat upper surface and may have one or two roots. Their shape is distinguished by two cusps or small pyramidal shapes on top.

Molars

• The 12 molars fill the rest of the adult jaw. Even more than the bicuspids, molars are responsible for the chewing and grinding of food; in fact, the word "molar" is derived from the Latin "mola," which means "mill." They are distinguished from the bicuspids by their larger size, flatter crowns and 2 to 4 roots.

Wisdom Teeth

• Technically, the wisdom teeth are molars -- the third or back most molars on both jaws and sides of the mouth -- to be specific. Since they are the last permanent teeth to erupt, sometimes there is not enough room in the mouth and they become impacted. Though they come in straight for most people, those with impacted wisdom teeth must have them removed to prevent further dental problems.