Tooth Decay - Types of teeth



The permanent teeth number 32. In advancing from deciduous to permanent teeth, the human gains six teeth in the lower jaw, or mandible , and six in the upper jaw, or maxilla , of the mouth. In general, each kind of tooth appears first in the lower jaw. The usual ages for the appearance of the permanent teeth are as follows:

LOWER UPPER
incisors 6-8 yrs 7-9 yrs
cuspids 9-10 yrs 11-12 yrs
bicuspids 10-12 yrs 10-12 yrs
first molars 6-7 yrs 6-7 yrs
second molars 11-13 yrs 12-13 yrs
wisdom teeth 17-21 yrs 17-21 yrs

An incisor is designed to cut off particles of food, which is then pushed by muscles of the tongue and cheeks to teeth farther back in the mouth for grinding. The front teeth, one on each side, upper and lower, are central incisors. Next to each central incisor is a lateral incisor.

A cuspid is so named because it has a spear-shaped crown, or cusp . It is designed for tearing as well as cutting. Cuspids sometimes are called canine teeth or eyeteeth; canine teeth owe their name to the use of these teeth by carnivorous animals, such as dogs, for tearing pieces of meat. There are four cuspids in the mouth, one on the outer side of each lateral incisor in the upper and lower jaws.

Teeth

Bicuspids sometimes are identified as premolars . The term “bicuspid” suggests two cusps, but a bicuspid may in fact have three cusps. The function of the bicuspids is to crush food passed back from the incisors and cuspids. The permanent set of teeth includes a total of eight bicuspids.

The molars , which also number eight and are the last teeth at the back of the mouth, are the largest and strongest teeth, with the job of grinding food. The third molars, or wisdom teeth, are smaller, weaker, and less functional than the first and second molars.



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