The adult human mouth contains 32 permanent teeth. There are four layers to a tooth. The pulp is the middle of the tooth made up of soft connective tissue, blood vessels and nerves. The cementum, made of minerals, covers the pulp and helps to anchor the tooth. The majority of the tooth is made up of dentin which gives the tooth its shape. The shiny outer surface of the tooth is made of enamel, the hardest substance in the human body according to the Dental Health Site. There are four types of teeth that work together to help to tear and chew food needed for nutrition.
Incisors, also called cutting teeth, have flat surfaces with a straight, sharp edge. The front 4 top and bottom teeth are incisors, making 8 total incisors in the human mouth. These teeth work to cut and bite food into small pieces that can be chewed by the other teeth. Incisors have one long conical root that anchors it into the jaw bone.
The primary (also known as baby teeth) incisors are the first teeth to erupt. The bottom incisors usually begin to appear between 6 and 10 months of age, according to The Online Knowledge Magazine, while the top incisors appear between 8 and 12 months of age.
The canine teeth are the strong, pointed teeth found in the corners of the mouth. There are 4 canine teeth, two on top and two on bottom. The canine teeth surround the incisors. These teeth are used to shred and tear food.
The top canine teeth are often also called the eyeteeth. The canine teeth are the longest teeth in the mouth and extend beyond the other teeth. Like the incisors, the canine teeth have one single root. In addition, the canine teeth are the only teeth with a single cusp (a rounded projection on the chewing surface of a tooth), according to Forensic Dentistry Online.
Behind each canine tooth are two pre-molar teeth, also known as bicuspids. This makes a total of 8 pre-molar teeth in the adult human mouth. The pre-molars have a flat upper surface with at least 2 cusps and are used for chewing and crushing food. The pre-molar teeth have either 1 or 2 roots.
The teeth found furthest back in the mouth are the molars. There are 12 molars in the adult human body, 3 in each quadrant. The molars have the largest upper surface providing for the maximum chewing and grinding of the food. This is important since the molars are the final teeth food meet before swallowing. Molars have between 2 and 4 roots to anchor them into the jaw bone.
The third molars are also known as the wisdom teeth. These molars are the last to appear, erupting in the late teens to the twenties. The wisdom teeth are often removed due to lack of space in the jaw or because of a partial eruption that can lead to infection.