The Trouble With Teeth
Most people go through three smiles in a lifetime- the milk teeth, an adult set, and the pair the dentist makes It's worthwhile trying to keep your own
Few people, if any, have not at one time had trouble with their teeth, whether it be a slight toothache, a painful wisdom tooth or a serious abscess. And because we constantly use our teeth for eating, talking or just smiling, we tend to be more conscious of tooth trouble than of other minor complaints.
Human teeth are diphyodont - the childhood set is replaced later in life by a completely new set - and in this respect they are unique among the organs of the body.
The childhood or milk teeth are 20 in number and appear during the first two years of life. This set is replaced, normally between the sixth and eighteenth years of life, by the permanent set of 32 teeth. Both sets contain teeth of different shapes which have different functions. The milk dentition is made up of incisors, canines and molars which are used for biting, tearing and chewing respectively. Each quadrant (for example the lower jaw on the right hand side) contains two incisors, one canine and two molars. The permanent set of teeth contains the same number of incisors and canines, but also one extra molar and three other teeth called premolars between the canines and the molars.
As soon as the teeth are fully erupted they cease to grow (although they are still living structure) and gradually wear away with continual use.
A tooth is a complex structure consisting of inorganic salts of calcium and living tissue derived from skin. Its external features are a crown, visible above the gum, and one, two or three roots which are buried in the gum and which occupy a socket, the alveolus, in the jawbone (the mandible in the case of the lower teeth and the maxilla for the upper ones). The roots are attached to the bone by the periodontal membrane, which also acts as a shock absorber to take the enormous forces (up to 400 pounds) which the tooth must bear during chewing.
The inside of a tooth consists of a hard wall and a hollow enclosed space filled with a soft core of dental pulp, often called the 'nerve' of the tooth. The pulp is the living part of the tooth and contains connective tissue and the network of nerves and blood vessels which supply food material to the tooth. The hard wall is made up of three kinds of material. Dentine, or ivory, borders the pulp cavity and makes up the body of the entire tooth.
Below the gum this is covered by cement, a substance which has some resemblance to bone. The cement layer is thickest at the ends of the roots, and becomes thin at the neck of the tooth - the junction of the roots and the crown at the edge of the gums. The crown of the tooth is covered by a white shiny material called enamel. This is almost completely made up of inorganic calcium compounds, and is the hardest of all animal tissues. But it will dissolve in acids with a concentration no greater than lemon juice! As with cement, the enamel is thickest on the top of a tooth (in this case where it bears the grinding action of other teeth) and becomes thinner at the neck.
The eruption of teeth is a long, and by no means smooth, process. At birth no teeth are visible and the first ones, usually the central incisors, appear at about the age of six to nine months. Working outwards from the center (the way teeth are usually numbered by the dentist) the rest of the teeth gradually appear until the complete milk dentition has erupted at the age of about two years. At about age six the permanent teeth begin to push their way through the gums, dislodging the milk teeth as they do so. But the eruption of the permanent teeth follows a slightly different pattern from that of the childhood ones. The first molar is usually the first to appear, followed, at approximately the rate of one tooth in each quadrant per year, by the incisors, the premolars and then the canines and the second molar. The third molar, or wisdom tooth as it is often called, is the last to appear, and this often does not erupt until the age of 18 or even later.
Many problems are associated with the eruption of teeth. The irritation of the tooth as it pushes through the gum may cause a number of symptoms, most commonly irritability and loss of sleep, but the infant may also refuse to eat which could lead to loss of weight. In some cases teething can be especially troublesome and may lead to general symptoms such as diarrhea, coughing, skin eruptions and sometimes convulsion. Treatment is fairly straightforward and aims to induce the teeth to erupt quickly, and with as little trouble as possible. The child may be given a rusk or something hard such as a bone or teething ring which it can press against its gums.
Some adults experience considerable pain during the eruption of their wisdom teeth. This is usually because there is not enough room for the new tooth between the second molar and the vertical portion of the jaw, and so a person with a smaller than normal jaw will suffer most. Sometimes a tooth begins to grow into the vertical portion of the jaw bone, or may even erupt in the wrong direction and impact in other parts of the bone. But even if the wisdom tooth does not cause pain, the gum flap over the tooth often prevents proper drainage and food debris collects, forming a breeding ground for bacteria, which eventually leads to decay. The usual remedy for trouble with wisdom teeth is to remove them.
For a number of hereditary or environmental reasons the permanent teeth may be irregular when they erupt. There may be defective development of the jaw bone, a highly arched palate or slowness in casting the milk teeth, resulting in teeth of both sets being present at the same time. The result is overcrowding of the teeth, sometimes leading to impactation of the teeth which are last to erupt- the canines or the wisdom teeth for example - or to distortion of the position of the teeth. Slight irregularities usually disappear as the jaw grows, but more serious deformities may need corrective measures such as the removal of some of the teeth or the wearing of an elastic device or brace in the mouth to keep constant pressure on the deformed teeth.
When the teeth are developing in the embryo, formation of the enamel may lead to small fragments of tissue being left deep in either the mandible or maxilla.
Later in life these fragments may start to grow for some reason, and as they do the inner cells of the fragments die. This leads to the formation of a fluid-filled ball of tissue, or cyst, inside the bone, and it may go on growing and reach a great size before it causes any symptoms, such as swelling of the bone or infection of the fluid-filled cavity. The cyst must then be removed surgically, and the resulting space carefully protected from infection until it heals.
An adequate diet is of course important in the development and maintenance of healthy teeth. Because teeth contain large amounts of calcium, foods such as milk, cheese and green vegetables are vital, not only for children, but for adults and especially pregnant mothers as well. But for calcium to be of any use to the body, vitamin D is also necessary. This is found in eggs, milk, butter, liver and fish oils, but not in plant foods, and this is one reason why strict vegetarians often have weaker teeth than normal.
Caries, or decay, is certainly one of the most common of the diseases of the teeth. It is most frequent among civilized peoples whose diet contains a large proportion of refined carbohydrates (sugars), and most commonly seen in children and young adults. Although its exact cause is not certain, it is known that the micro-organisms found in the tartar, or deposits of food particles and saliva on the teeth, play an important part. By fermenting sugars in the food particles, the micro-organisms produce acids which attack and dissolve the enamel.
Decay usually begins in some groove or pit in the enamel or between the teeth, and when the process has made a small opening in the enamel, it can spread rapidly within the dentine. Eventually the cavity which is produced reaches the pulp, which is then killed, and this may occur with or without pain depending on the speed of the process and the patient's threshold to pain. Pain (toothache) is usually the result of the cavity produced by decay reaching and thus exposing the pulp. Many general conditions, such as digestive disturbances, or pregnancy, render a person more liable to toothache than when in good health, and exposure to cold, a hot drink or some sweet or acid food can often start an attack.
But often the first sign a person may get, apart from discoloration, may be a tooth suddenly caving in during a meal. However, when the pulp is dead it may putrefy and cause infection around the root and in the jawbone, and if this area becomes acutely infected severe swelling and pain may result. In some cases there may be long-standing infections subject to sudden 'flare-ups'.
Generally three factors are involved in the development of caries - the resistance of the teeth, the presence of micro-organisms and a suitable food material from which the micro-organisms can obtain nourishment and produce acids as a by-product.
Experiments on rats have shown that the latter two factors are involved in caries. Rats which were kept germ-free did not develop caries, showing the involvement of bacteria; and if normal rats were fed a sugary diet direct to their stomachs, thus by-passing the bacteria in the mouth, caries was again avoided, demonstrating the involvement of sugars.
But the resistance of the teeth is not quite so simple. Certain chemicals, present only in minute quantities, may alter the chemical composition of the enamel in some way, and hence change its resistance to attack by acids. In some parts of the United States, where the soil contains unusually large quantities of selenium, the incidence of caries is abnormally high.
People take in this selenium in eggs and milk from animals feeding on grass growing on this selenium soil. But the water supply too can contain traces of chemicals which affect the resistance of teeth. Selenium is not carried in water supplies, but fluorides are. Fluorides have the effect of increasing the resistance of the teeth to acid attack, and in areas where the natural content of fluorides in the water is high, the incidence of caries is relatively low.
This of course suggests a means of widespread control of dental caries, although attempts to fluorinate drinking supplies have met with great resistance from people who dislike the thought of anything being added to their water. Another way of obtaining fluorides is to have traces of it in toothpaste and a number of brands containing them are now available.
A more satisfactory way of preventing caries is to keep teeth clean. But for a number of reasons, such as bad quality of teeth or bad arrangement or overcrowding in the jaw which leads to food particles accumulating between the teeth, it is often not possible to keep teeth perfectly clean.
Decay rarely appears on free, smooth surfaces which are exposed to the rubbing of lips and tongue or the scouring of food, nor among primitive people who live on coarse food that requires a great deal of chewing.
Once a tooth has developed decay, it requires dental care. If a tooth is dead, or so far decayed as to be useless for chewing, it is often best to remove it, but in less advanced cases the dentist can remove the decay and fill the tooth with an inert material which will withstand the stress of biting. As caries can develop without symptoms it is important to visit the dentist regularly so that the decay can be stopped in the early stages.
One of the complaints which may develop from a carious tooth is a gumboil an inflammatory condition associated with the rot of a tooth, which gives a dull throbbing pain and may proceed to an abscess. The first sign is that one tooth may become painful and seem raised above the others. In the early stages the pain may be relieved by tightly clenching the teeth, but in a few days the tooth becomes very tender. Then a thickening forms at the side of the tooth but the pain from this may also be relieved by pressure or by holding a pad of cotton wool or other soft mass between the gum and cheek. After some days the pain lessens and either the swelling subsides or an abscess forms. An abscess is a localized collection of pus - a mixture of dead white blood corpuscles, dead tissue cells and dead bacterial cells.
There are sensations of warmth, and a general swelling, redness and pain. The abscess later becomes distended, and finally bursts, when the temperature returns to normal and the pain disappears and the small wound heals rapidly. If there is a cavity in the tooth this should first be stopped with a small plug of cotton wool soaked in oil of cloves, or with a mixture of zinc oxide and oil of cloves. If the pain does not go immediately, then the best course is probably to remove the tooth. The inflammation can be relieved in the early stages by painting the gum with tincture of iodine (iodine dissolved in alcohol) , and if the swelling is considerable the gum must be scarified down to the bone on the outer side between the gum and the cheek. Speed of treatment is essential here if the skin is becoming red all over, as this is a sign that the abscess is likely to burst through the cheek and leave an unsightly scar.
Bleeding from the gums can result from a number of conditions, of which the usual ones are inflammation of the gums, or gingivitis, and pyorrhea, also called periodontal disease. Gingivitis is a chronic disease which occurs more often in later life and is more common in women than in men. The gums are congested and often bleed during chewing or brushing. They are also very tender, and a deposit of tartar collects on the teeth.
Later the gums waste away and shrink at the margins, leaving the necks of the teeth exposed. Indigestion, diarrhea and anemia are common side effects of this disease. Pyorrhea is thought to be caused by inadequate roughage in the diet and inadequate care of the teeth. This causes an excessive deposit of tartar and a proliferation of bacteria on the teeth, which in turn lead to ulceration and inflammation of the gums. The effects of the condition are related to the general health of the individual, and it becomes worse if the person has another disease. It also worsens somewhat during pregnancy. Pain is not a feature of periodontal disease, but there may be an unpleasant taste in the mouth and bad breath, and, in the later stages, bleeding gums and discharge of pus.
Careful hygiene of the mouth is the best cure of these diseases, although at one time the wholesale removal of teeth was practiced as a cure for pyorrhea. Removal of tartar and regular use of an antiseptic mouthwash are both useful. Cleaning the teeth is vital to health; and regular visits to the dentist are a must.
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