THE CARE OF THE MOUTH
=Sickness often begins in the Mouth.=--A clean mouth and sound teeth
have much to do in keeping one well. The germs which cause nearly a
half million deaths in the United States every year enter the body
through the mouth. If the mouth is unclean, only one or two disease
germs entering it may remain there and grow.
[Illustration: FIG. 30.--The teeth of the upper jaw at eleven years of
age.]
It is just as important to wash the mouth two or three times each day
as it is to wash the hands and face. A few germs of diphtheria, sore
throat, or tuberculosis are likely to get into the mouth any day, but
if the mouth and teeth are well washed with a brush morning and night,
the germs will not have time to grow and cause sickness.
=The Teeth.=--The first twenty teeth that appear are called the _milk
set_. The eight front teeth grow out during the first year of life and
back of these twelve others appear during the second year. Between the
seventh and the tenth year all of the milk teeth are lost because
others grow beneath them and push them out.
[Illustration: FIG. 31.--The full set of teeth on the right side at
twelve years of age. The numbers show at what year of age each one
grows out of the gum.]
The first four teeth of the second set appear in the sixth year, just
behind the last milk teeth (Fig. 30). These teeth should be watched
very closely and at the first sign of decay you should go to the
dentist. As the milk teeth get loose and come out, the second set of
teeth take their places.
If you are ten or eleven years old, you should have twelve good teeth
in the upper jaw and the same number below. The last ones to break
through the gums are the four wisdom teeth at the back of the mouth.
They appear after the seventeenth year.
The front teeth are called _incisors_ because they are used to cut the
food. The back teeth are named _molars_ because they are used in
grinding the food.
[Illustration: FIG. 32.--Photograph of teeth not kept clean, showing
how germs and a sour substance called acid eat holes in them and thus
cause decay and toothache.]
=Toothache.=--Toothache is a common ailment, and yet it can be
entirely prevented. A tooth does not ache until it has a hole in it.
The tender nerve within gives us warning that it is being hurt. The
dentist can stop the ache and mend the tooth so that it will not ache
again. Look at your teeth every month and feel about them with a
wooden tooth-pick to know when the decay begins. If the little holes
are mended as soon as found, you will never have toothache, and you
can keep your teeth as long as you live.
[Illustration: FIG. 33.--Slice down through a tooth showing _f_, the
enamel, and _d_, the soft pulp with nerves and blood tubes from the
root at _h_.]
=How to keep the Teeth Sound.=--Every tooth is covered with a layer of
hard shining substance called _enamel_ (Fig. 33). So long as this is
unbroken the softer bony part of the tooth cannot decay. At the base
of the tooth where the gum joins it the enamel is very thin, so that
the scratch of a pin or other instrument may break it.
Never pick the teeth with a pin or needle. The biting off of thread,
finger nails, and other hard material may crack the enamel. It may
also be softened and eaten away by acid formed where food remains
about a tooth. For this reason a quill or wooden pick or piece of
tough thread, called _dental floss_, should be used to clear the teeth
of food after each meal. Slimy matter collects over the whole surface
of the teeth, and is likely to cause decay in spots unless it is
cleaned off night and morning with brush and water. The chewing of dry
crusts of bread or crackers strengthens the teeth and keeps off decay.
=Why Candy and other Sweets cause the Teeth to Decay.=--A sour
substance called acid usually starts the decay of a tooth by eating
through the enamel. Germs change sugar and other sweets into an acid.
The acid is not made at once. An hour or more is needed for the germs
to grow to form the acid. If, after eating sweet foods, the mouth is
well cleaned, no acid will be formed. Sugar and candy do not,
therefore, spoil the teeth unless it is left sticking about them.
=How to brush the Teeth.=--Every boy and girl should own a toothbrush.
_The teeth should be brushed every night and morning and kept white._
Yellow or gray slimy teeth are very ugly. The teeth should be brushed
on the inside as well as on the outside. It is best to brush the teeth
crosswise for two minutes and then spend another two minutes brushing
the upper teeth downwards and the lower teeth upwards. This prevents
pushing the gum away from the teeth. Plenty of water should be used
with the brush, and a little good powder is helpful once a day.
=How the Dentist can Help.=--Sometimes the milk teeth do not get loose
so that they can be pulled with the fingers at the right time. The
second teeth then come in at one side and may never get straight in
place. They then spoil the appearance of the face and do poor work in
chewing. The dentist should be asked to help straighten the teeth as
soon as they appear crooked.
[Illustration: FIG. 34.--Exact drawing of the teeth of two persons.
Those in the lower picture began to decay over twenty-five years ago and
they were then filled so as to remain perfect. The teeth in the upper
picture began to decay less than ten years ago but were not filled.]
It is wise to have the dentist examine the teeth once or twice every
year and remove a limy substance called tartar collecting at their
base. The dentist can stop the decay in a tooth by cleaning out the
little hole and filling it with gold or some other material. It may
cause a little pain and expense to have the teeth filled, but it will
save a hundred times as much pain and expense later. The six year
molars need special care as they are likely to decay early. Even the
milk teeth often need filling so that they will not be lost too soon.
=Bad Teeth cause Sickness.=--When anything decays, it is full of
germs, and they are always giving off some poison. The poison may hurt
the body and is likely to make parts of the mouth sore and tender so
that other germs of disease can break through into the flesh. Disease
germs can easily lodge in the holes of decaying teeth, grow in
numbers, and finally cause diphtheria, sore throat, or other ailments.
Four out of every five children suffering from diphtheria or other
throat or ear troubles are found to have from one to ten bad teeth.
You must keep good teeth if you wish to be well and strong.
=The Value of Sound Teeth.=--Sound teeth which will do good work in
chewing food are worth more than a foot or an arm. If the foot or arm
is lost, the body is likely to get well and be as healthy as ever.
_The health of the whole body depends upon the work done by the
teeth._ Unless they do their part the stomach cannot get the food
ready for the blood.
A part of badly chewed food is turned into a poison farther down in
the food canal. This is what makes many people feel so tired and
miserable much of the time. Hundreds of men have been refused
admission to our army because they have poor teeth. Soldiers must be
strong and well to take long marches and fight battles. Sound teeth
give strength and health.
PRACTICAL QUESTIONS
1. Why should the mouth be washed out every day?
2. When do the milk teeth appear?
3. When are the milk teeth lost?
4. How many teeth have you?
5. How many show signs of decay?
6. How may toothache be prevented?
7. How may the teeth be kept sound?
8. Why do sweets cause the teeth to decay?
9. How should you brush your teeth?
10. Why should the dentist examine your teeth every year?
11. Why are sound teeth of great worth?