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Teeth are numerous, hard tissue structures in the mouths of humans. In
humans the teeth are composed of nan inner layer of dentin that, above the
gum line, is covered by a layer of enamel. Called the crown, this part of
the tooth is extremely hard. The root portion of the tooth is covered with
a bonelike substance called cementum. The root is embedded in the jawbone
and lies in a socket, where the cementum is attached to the adjacent bone
by a periodontal membrane, consisting of fine consecutive tissue fibers.
The tooth is also attached to the gum tissue (gingiva); at this connection
there is a slight depression called the primary dentition, emerges in
steps between the ages of 6 months and 2 years. between the ages of 6 and
13 years a second (and permanent) set of teeth sequentially replaces the
first. Between the ages of 18 and 21 years, 4 molars called wisdom teeth
emerge. The 20 primary teeth -4 central incisors, 4 canines (cuspids), and
8 molars- begin to develop pior to birth. They are eventually replaced-
beginning around the age of 6 -by 32 permanent teeth.: 4 central incisors,
4 lateral incisors, 4 cuspids, 8 bicuspids (premolars), and 12 molars.
The 4 wisdom teeth develop after the other 8 molars, as the jaws increase
in size. If this increase is insufficient, the wisdom teeth may become
impacted, that is wedged between the jawbone and other teeth, sometimes
resulting in pain and inflammation. The upper teeth, called maxillary, and
the lower teeth, called mandibular, are shaped in such a manner that they
interdigitate (fit together) when the jaws are closed. This fit is
essential for the teeth to function properly when biting food with the
incisors (front teeth) and when chewing and grinding food with the back
teeth (molars and premolars). The molars and premolars have large surfaces
with points (called cusps) and grooves so that they fit together extremely
well.
Human teeth are derived from both the mesodem (...
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