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.
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.