Hygiene Of The Teeth
( Originally Published 1917 )
Temporary and Permanent Teeth.—Our first teeth begin to grow out from the gums when we are only a few months old. There are twenty teeth in this first or temporary set, and the last of them generally appear by the end of the second year. These first teeth begin to loosen and fall out when a child is about six years old, but some of them re-
main until he is twelve or older. As the first or temporary teeth go, the second or permanent set come in to take their places. There are thirty-two of these permanent teeth. The last of them, the four "wisdom teeth," may not appear until sometime between the ages of seventeen and twenty-five years or even later.
The Different Kinds of Teeth.—The arrangement of the permanent teeth is shown in Fig. 28. Flesh-eating animals, such as the dog, have only tearing or biting teeth, and some of the grass-eating animals, such as the cow or horse, have only flat grinding teeth. We have both kinds—four sharp cutting teeth or incisors in the front of each jaw; six molars or flat grinding teeth at the back of each jaw; and two cuspids and four bicuspids (partly for cutting and partly for grinding) at the sides of each jaw.
The Structure of a Tooth.—The part of a tooth which we can see above the gum is called the crown. Underneath the gum is a root, by which the tooth is held in place (see Fig. 29). The greater part of the tooth is made of a hard bony substance called dentine. On the crown, this is covered with a still harder layer of smooth shining enamel, and on the root with cement. Inside the dentine is a soft mass of pulp containing nerves and blood vessels.
Tooth Decay and Its Causes.—When particles of food are left between the teeth, they decay and the chemicals produced by microbes act, on the enamel and gradually destroy it. When the enamel has been injured, the dentine underneath is rapidly attacked and at last, if the cavity is neglected, the decay reaches the nerves. Such decay of the teeth is known as dental caries (ka ri ez).
There is another very common and serious disease, called pyorrhea (pi o re' a), in which the microbes infect the edges of the gums. Teeth affected in this way may become loosened and finally fall out.
Effects of Tooth Decay.—Neglect of the teeth produces many bad effects. The odor from an unclean mouth is most unpleasant to other people. The teeth in such a mouth decay, and as they begin to grow sensitive, chewing is neglected, and the stomach is likely to be loaded with unchewed food. Contact with sweet or hard substances, or extreme heat or cold, may then result in aching teeth, and lead to painful visits to the dentist, to have the tooth filled—if it is not too late.
The evil effects of tooth decay are not limited to the teeth themselves. Recent studies have shown that the microbes which cause decay of the teeth may form poisons which affect the whole body. In some cases the microbes themselves, after growing in the tissues about the teeth, may get into the circulation and pass to other parts of the body, where they set up serious diseases, such as rheumatism and heart disease. A neglected tooth is a gateway through which some of our worst germ enemies may gain entrance.
Care of the Teeth.—The enamel is the natural protection of the teeth, and it is very important that it should not be injured. It is fairly brittle and may easily be chipped, so that one should be careful not to crack hard nuts with the teeth or to pick the teeth with hard objects which might splinter them.
On the other hand, thorough chewing of the food, and particularly of fairly hard foods like crusty bread, tends to polish the surfaces of the teeth and to prevent deposits on them. The coarse food which savage people eat helps to keep their teeth in good condition, and the more of such food we eat, the better it is for us. But as most of us do not eat enough hard foods, especial care is necessary to prevent decay and to keep the mouth healthy.
The most important aid in keeping the teeth in good condition is, of course, the toothbrush. It has been said that in an army—where the greatest care must be taken of the health of the soldier—his toothbrush ought to be in-
spected as systematically as his gun. The teeth should be brushed regularly night and morning, at least. It is well to brush them after each meal, because the sooner deposits of food are removed, the better. Once a day a good tooth powder should be used to aid in cleaning the teeth; or, better still, the toothbrush may be sprinkled with some,, mild food acid, such as vinegar, and the mouth may be thoroughly rinsed, after brushing, with a mixture of one part of vinegar to two parts of water.
At other times, the brush and plain water alone are sufficient.
The toothbrush should not be too large, and the bristles should be of medium hardness and so shaped that they will get between the teeth. Both sides and the top of the teeth should be thoroughly brushed. It is much better to brush down or up from the gums to the cutting edge instead of side-ways across the teeth, because when the brush passes side-ways the bristles do not get in between the teeth. The most effective method is to place the bristles of the brush firmly against the teeth, apply pressure as if trying to force the bristles between the teeth, and then give the brush a rotary or scrubbing motion. Care should be taken to go over both the back and front of the cutting teeth in both jaws, as well as the flat crowns of the grinding teeth. The gums above and below the teeth and the surface of the tongue should also be cleaned.
When the brushing is finished, lukewarm water should be taken into the mouth and forced between and around the teeth several times, by means of the lips, cheeks, and tongue. This is as important as the proper use of the toothbrush itself. The tooth toilet should take from three to five minutes.
Even the best use of the toothbrush will not always keep the spaces between the teeth entirely clean. If food particles collect in these spaces, a bit of dental floss may be passed up and down between the teeth, care being taken not to injure the delicate gums.
Dental Care of the Teeth.—In spite of all that we can do, a hard substance called tartar often deposits upon the teeth, and decay sometimes begins before we know it. Inspection of the teeth of school children usually shows that at least two out of three mouths seriously need dental attention.
It frequently happens that the teeth are crowded irregularly into the mouth instead of being evenly arranged. Such teeth are unpleasant in appearance and are likely to decay, because there are many cavities between them to catch bits of food. Since the teeth in distorted jaws do not meet properly, adequate chewing is impossible. The dentist can straighten teeth of this kind and improve the appearance and health of the child at the same time—if the matter is attended to early enough.
It is well to have the teeth examined by a good dentist at least twice a year. He will remove the tartar, polish the teeth, and care for any beginnings of decay. There will be only slight pain and little expense. If the teeth are not examined in this way, decay is likely to start somewhere; and when a toothache finally drives us to the dentist's chair, there is suffering in store, and it may be too late to save the tooth. It is as true here as elsewhere that Prevention is better than Cure.
QUESTIONS FOR DISCUSSION AND REVIEW
1. How many sets of teeth do we have? When do they appear? How do they differ?
2. What are the advantages in having teeth of various shapes?
3. Describe the structure of a tooth.
4. What causes teeth to decay?
5. What effect do decayed teeth have on the digestion?
6. Describe your ideal of what a set of teeth should be. Notice the people you meet and see how many have teeth which are ideal.
7. What danger is there in cracking nuts or biting thread with your teeth? In picking your teeth with a pin?
8. It is said that the peasants of Scandinavia, who eat much hard black bread, have fine teeth. Explain.
9. Name several means of keeping the mouth and the teeth clean.
10. What kind of toothbrush is best?
II. Describe the correct use of the toothbrush.
12. How often should the toothbrush be used?
13. A little girl in the slums of a big city said that her father had a toothbrush, but that she didn't like to use it. Was she right or wrong? Explain.
14. Most large public school systems require an examination of the teeth of all school children. They also provide dental clinics where the necessary work on teeth is done at a nominal price. Why is this considered necessary?
15. Why should crooked teeth be straightened?
16. How often should teeth be examined by the dentist?