Tooth Anatomy

美人帐下跳着舞 · 发表于 2009-4-12 01:55:15

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People use their teeth to bite and chew food - they are the first step in the digestion of food. The long, sharp canine teeth tear up food (like meat). The wide, flat molars grind and mash up food. While we chew food, the tongue pushes the food to the teeth and saliva helps digestion and wets the food. Teeth also help us say certain sounds.

People have two sets of teeth in their lives, the primary teeth (also called the baby, milk or deciduous teeth) and the permanent teeth (also called the adult or secondary teeth). Children have 20 primary teeth; they are replaced by the permanent teeth by about age 13. Adults have 32 permanent teeth. Primary Teeth:
Most babies are born with no visible teeth -- the teeth are forming inside the gums. The 20 primary teeth (also called baby teeth or first teeth) erupt (poke through the gums) over the time from when a baby is from about 6 months to a year old. Permanent Teeth:
Primary teeth fall out and are replaced by 32 permanent teeth (also called the adult teeth). This happens over the time from when a child is from about 6 to 14 years old. As a permanent tooth forms under the gums and in the jawbone, the roots of the primary tooth it is replacing dissolve. Then the primary tooth becomes loose and falls out. The permanent tooth will fill the space. Wisdom Teeth:
Wisdom teeth (also called the third molars) are molars that usually erupt from the ages of 17 to 21.

Tooth Glossary: Cementum - a layer of tough, yellowish, bone-like tissue that covers the root of a tooth. It helps hold the tooth in the socket. The cementum contains the periodontal membrane. Crown - the visible part of a tooth. Dentin - the hard but porous tissue located under both the enamel and cementum of the tooth. Dentin is harder than bone. Enamel - the tough, shiny, white outer surface of the tooth. Gums - the soft tissue that surrounds the base of the teeth. Nerves - nerves transmit signals (conveying messages like hot, cold, or pain) to and from the brain. Periodontal membrane/ligament - the fleshy tissue between tooth and the tooth socket; it holds the tooth in place. The fibers of the periodontal membrane are embedded within the cementum. Pulp - the soft center of the tooth. The pulp contains blood vessels and nerves; it nourishes the dentin. Root - the anchor of a tooth that extends into the jawbone. The number of roots ranges from one to four.