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Human
teeth also serve major functions other than chewing. The teeth
are directly involved in the process of speech, acting as a
brace against which the tongue presses in the formation of
certain sounds. The teeth also affect the dimensions and the
expression of the face, the appearance of which may be
unpleasantly modified by the loss of neighbouring teeth or by
any irregularity in tooth growth or colouring. |
Why do
we have teeth?
Have you ever really thought about why people need teeth? They
might be more important than you think.
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Why
teeth are important?
Teeth bite and chew food so that it is small enough to be
swallowed.
Teeth help you to form words so that you can speak properly.
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MILK TEETH |
Your first
teeth are called deciduous teeth (say dee-sid-you-us). (They
can also be called milk teeth, baby teeth or primary teeth.)
They are called deciduous because like the leaves of a
deciduous tree you lose them.
You have 20 deciduous teeth and they start growing into your
mouth from about 6 months of age.
All 20 teeth have grown into your mouth by about two and a
half years of age.
From about 6 years of age until 12 years of age you start to
lose them, BUT that doesn't mean you don't have to look after
them.
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TYPES
OF TEETH |
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The 20
deciduous, or baby, teeth in a child’s mouth are gradually
replaced by the permanent array of 32 teeth illustrated here.
The 8 incisors (4 on the upper jaw and 4 on the lower) have a
straight, sharp edge for cutting and biting. The 4 pointed
canines are specialized for tearing. The 8 bicuspids, or
premolars, missing among the deciduous teeth, have grinding
surfaces, as do the 12 more massive molars. In parentheses are
the ages at which these teeth appear. The third molars, absent
in some people, are called wisdom teeth.
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Incisors |
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The four front
teeth in both your upper and lower jaws (a total of eight) are
incisors. The pair of teeth at the center of your mouth, top
and bottom, are called the central incisors. And the teeth on
each side of the central incisors are the lateral incisors.
All the incisors are broad, flat teeth with a narrow edge good
for cutting or snipping off pieces of food. They have a single
root.
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Canines |
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Sometimes called eyeteeth or cuspids, canines are the longest
and most stable teeth in the mouth. They are thick and come to
a single sharp point. They are ideal for ripping and tearing
at foods that might be tough, such as meat, and for piercing
and holding. They have a long single root.
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Premolars |
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Next to
each canine are two premolars (a total of eight). Also called
bicuspids, premolars are a cross between canines and molars.
They have sharp points for piercing and ripping, but they also
have a broader surface for chewing and grinding. On the upper
jaw, the first premolars (directly next to the canines) have
two roots, and the second premolars have one root. On the
lower jaw, all premolars have one root. |
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Molars |
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The last three
upper and lower teeth on both sides of your mouth are the
molars (a total of 12). They are numbered first, second or
third molars depending on their location. The first molars,
also called 6-year molars, are those closest to the front of
the mouth, directly next to the second premolars. The third
molars are also called the wisdom teeth. They are the last
teeth, farthest back in the mouth on all sides. In between are
the second molars, also called 12-year molars. Molars are
large teeth with broad surfaces designed for crushing,
grinding and chewing food. On the upper jaw, the molars have
three well-separated roots. On the lower jaw, the molars have
two roots |
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STRUCTURE
OF A TOOTH |
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Human
teeth consist of an external portion, called the crown, and a
root that is embedded within the jaw. The outer layer of the
crown is composed of calcified tissue known as enamel—the
hardest substance in the body. Inside the enamel is the
dentine, a bonelike substance extending from the inner surface
of the enamel into the jaw to form the root. Covering the
dentine of the root is a thin layer of a hard tissue called
cementum. The roots are held in place by elastic fibres that
constitute the periodontal membrane, which extends from the
cementum to a thickened layer of bone, known as the lamina
dura, within the jaw.
The dentine of the crown encloses the pulpal chamber, which
penetrates into the root as the root canal. Passing through
the root-canal opening at the end of the root are blood
vessels, nerves, and connective tissue, which fill the root
canal and pulpal chamber |
Teeth
have two parts,
1.The crown is the part of the tooth we can see in our mouths.
2.The root of the tooth which is 'planted' into the jawbone to
keep the tooth steady while it is doing its job.
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Teeth
have three layers:
1.Enamel, (say ee-nam-el) a hard protective outer layer
covering the crown of the tooth.
2.Dentine, (say den-teen) a second protective layer covering
the nerve of the tooth.
3.Pulp, (also called the nerve) the soft middle of the tooth
that has a blood supply and nerve endings
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Courtsey
www.lilypads.com.sg
www.cyh.com
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REFERENCES:
microsoft Encarta
www.lakshdeep.com |
