A Handbook of Health by Woods Hutchinson (learn to read books .txt) 📖
- Author: Woods Hutchinson
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The shape and position of the teeth literally make the lower half of the face and give it half its expression. A properly grown and developed set of teeth not only is necessary to health and comfort, but helps greatly to make the face and expression attractive or unattractive. Few faces with bright eyes, clear skin, and white, regular, well-kept teeth are unpleasing to look at. Beauty and health are closely related, and we ought to try to have both. In fact, nine times out of ten, what we call beauty is the outward and visible sign of inward health. The healthier you are, the handsomer you'll be.
It is particularly important to understand the natural growth and proper care of the teeth because there are few organs in the body for which we are able to do so much by direct personal attention. Our stomachs, our livers, and our kidneys, for instance, are entirely out of sight, and more or less out of reach; but our teeth are both easily got at and in full view; and, to a large degree, upon the care that we give them while they are young, will depend not only their regularity and whiteness, but also the length of their life and the vigor and comfort of our digestion all our lives.
The first thing to be remembered about the teeth is that, hard and shiny and different from almost everything else in the body as they look, they are simply a part of the skin lining the mouth, hardened and shaped for their special work of biting and chewing. Much of the care needed to prevent decay should be given, not to the teeth themselves directly, but to the gums and the mucous membrane of the whole mouth. The gums and the mouth literally grew the teeth in the first place; and when they become diseased, they secrete acids which slowly eat away the crowns and roots of the teeth. Their diseases come chiefly from irritation by decaying scraps of food, or from the blocking of the nose so that air is breathed in through the mouth, drying and cracking the soft mucous membrane. After the acids from the diseased gums have attacked the teeth, the poisons of the germs that breed in the warmth and moisture of the mouth cause the teeth to decay. Eight times out of ten, if you take care of the gums the teeth will take care of themselves.
Structure of the Teeth. The upper half of the tooth, which pushes through and stands up above the jaw and the gum, we call the crown; and this is the portion that is covered with enamel, or "living glass." The body of the tooth under the enamel is formed of a hard kind of bone called dentine. The lower half of the tooth, which still is buried in the jaw, we call the root. Wrenching the lower or root part of the tooth loose from its socket in the jaw is what hurts so when a tooth is pulled. The crown of the tooth is hollow, and this hollow is filled with a soft, sensitive pulp, in which we feel toothache. Tiny blood vessels and nerve-twigs run up from the jaw to supply this pulp through canals in the roots of the tooth.
(Lengthwise section.)
E, enamel; D, dentine; P, pulp cavity; C, cement; B, blood vessels; N, nerve.
Kinds of Teeth. If you look at your own teeth in a mirror, the first thing that strikes you is your broad, white, shiny front teeth, four above and four below, shaped like the blade of a rather blunt chisel. Their shape tells what they are used for. Like chisels, they cut, or bite, the food into appropriate sizes and lengths for chewing between the back teeth; and from this use they are called the incisors, or "cutters." From having been used for so many generations upon the kind of food we live on, they have grown broader than the canines, the teeth next to them, and almost as long.
The canines are of a cone-like shape, although it is a pretty blunt cone, or peg. Those in the upper jaw lie almost directly under the centre of each eye, and are called the "eye-teeth"; though their proper name, from the fact that they are the most prominent teeth in the dog, is the canine teeth. These are our oldest and least changed teeth; and as you might guess from their shape, like a heavy, blunt spear-head, were originally the fighting and tearing teeth, and still have the longest and heaviest roots of any teeth in our jaws. If you slip your finger up under your upper lip, you can feel the great ridge of this root, standing out from the surface of the gum.
Lastly, looking farther back into our mouths, we see behind our canines a long row of broad, flat-topped, square-looking teeth, which fill up the largest part of our jaws. Again their shape tells what they are used for. They are not sharp enough to cut with, or pointed enough to tear with, but are just suited for crushing and grinding into a pulp, between their broad, flat tops, any food that may be placed between them; and from this grinding they are called the molars, or "mill" teeth. If you will look closely at the back ones, you will see that each of them has four corners, or cusps, with a cross-shaped, sunken furrow in the centre, where they come together. After they have been used in grinding food for some years and rubbing against each other, these little corner projections become worn away, and their tops become almost flat. Those in the upper jaw have three roots, and those in the lower jaw have two, so that they are solidly anchored for their heavy, grinding work. The first two molars in each jaw, behind the canines, are smaller than the others and made up of only two pieces instead of four, and hence are called the bicuspids, or "two-cusped" teeth.
As we are what the scientists call an omnivorous, or "all-devouring," animal, able to eat and live upon practically every kind of food that any animal on earth can deal with,—animal and vegetable, soft and hard, wet and dry; fruits, nuts, crabs, roots, seaweeds, insects, anything that we can get our teeth into,—we have kept in working condition some of every kind of teeth possessed by any living animal; and the most important rule for keeping our teeth in health is to give all these kinds something to do.
Just as in other animals the teeth appear when needed, and grow into the shape required, so they grow in our own mouths when they are wanted, and of the size and shape required at the time. We are born without any teeth at all; and it is only when we begin to need a little solid food added to our milk diet,—when we are about seven months old,—that our first teeth appear; and these are incisors, first of all in the lower jaw. Then, at average intervals of about three months, the other incisors and the canines appear and, last of all, the molars, so that at about two years of age we have a complete set of twenty teeth. These are called the milk teeth.
Most animals (mammals) have formed the habit of growing two sets of teeth—a smaller, slighter set for use during the first few months or years of life, and a larger, heavier set to come in and take their place after the jaws have grown to somewhat more nearly their permanent size. In our mouths, at about seven years of age, a larger, heavier tooth pushes up behind the last milk tooth,—called the "seventh year molar,"—the milk teeth begin to loosen and fall out, and their places are taken by other new teeth budding up out of the jaw just as the first set did. These take a still longer time to grow, so that the last four of the full set of thirty-two do not come through the gums until somewhere between our eighteenth and twentieth years. These last four teeth, for the rather absurd reason that they do not appear until we are old enough to be wise, are known as the "wisdom teeth." Instead of being, as one might expect, the hardest and longest-lived of all our teeth, they are the smallest and worst built of our molars and among the first of our permanent teeth to break down and disappear. Not only so, but our jaws are so much shorter than they were in the days when man fought with his teeth and knew nothing about cooking and had no tools or utensils with which to grind and prepare his food, that there is scarcely room in them for these last teeth to come through. They often cause a great deal of pain in the process, and may even break through at the side of the jaw and cause abscesses and other troubles.
The "second teeth" are shown fully formed in the gums, ready to push out the milk teeth. The wisdom teeth, which appear later, cannot be shown at this stage.—After Gray.
Care of the Teeth. The most important thing for the health of any organ in the body is to give it plenty of exercise, and this is especially true of our teeth. This exercise can be secured by thoroughly chewing, or masticating, all our food, of whatever sort, especially breads, biscuits, and cereals. Thorough chewing not only gives valuable exercise to the teeth, but, by grinding up these foods thoroughly, makes them easier for the stomach to digest; and, by mixing them well with the saliva, enables it to change the starch into sugar. Meats, fish, eggs, cheese, etc., do not need to be mixed with the saliva, nor to be ground so fine for easy digestion in the stomach, and hence do not require such thorough chewing, though it is better to make a rule of chewing all food well. We can exercise our teeth also by eating plenty of foods that require a good deal of chewing, especially the crusts of bread, and vegetables such as corn, celery, lettuce, nuts, parched grains, and popcorn.
It is most important to keep the nasal passages clear and free, and the teeth sound and regular by proper dental attention, so that the jaws will grow properly, and each tooth will strike squarely against its fellow in the opposite jaw, and both jaws fit snugly and closely to each other, making the bite firm and clean, and the grinding close and vigorous. If we are mouth-breathers, our jaws will grow out of shape, so that our teeth are crowded and irregular and do not meet each other properly in chewing. Pressure upon the roots of the teeth, from meeting their fellows of the opposite jaw in firm, vigorous mastication, is one of the most important means of keeping them sound and healthy. Whenever a tooth becomes idle and useless, from failing to meet its fellow tooth in the jaw above or below properly, or from having no fellow tooth to meet, it is very likely to begin to decay.
The next important thing in keeping the
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