I SUPPOSE YOU COULD call me one of your body's blue-collar workers. I am not a brilliant chemist like your liver, or a dedicated slave like your heart. I am the most perishable part of your body whilst you are alive and, if I survive you the most durable after death. It's quite possible that I will be around several thousand years after the rest of you is dust.
I am your upper right canine, or "eye", tooth. With my twin, the left upper canine and our two opposite numbers in the lower jaw, I am part of a team that totaled 32 when you began your adult life. When you eat, we teeth start up the digestive process and contribute to your enjoyment of eating - food wouldn't taste like much swallowed whole.
Some of our attributes are rather striking. We have one bite for soft foods, another for hard, and a sensing device that tells us which to use. We can withstand pressures that would make jelly of other organs. Kidneys, skin and most of the components of your body can do some self-repairs when injured. We can't. Injure us and we stay injured.
My right to speak for the other teeth in your mouth? I think, perhaps, the eyetooth is the most interesting. In your superstitious past; it was thought that my roots were so long that they reached to the eye. People where afraid that if I were pulled out, the eye would become diseased. Even though you now know this is nonsense, you still say you would give your eyeteeth for something you want badly.
We teeth may have started out as scales on fish in ancient seas. But gradually, as life on land began, we changed form and position and became teeth. At birth, you had quite a mouthful of us, 52, buried in your gums. We weren't fully formed, but the maturing of 20 "baby" teeth was well under way, including enamel coating. When you where a newborn, your jaw was small and poorly developed, your face modeled for nursing, not chewing. There was barely room for the baby teeth, and not nearly enough for an adult set of 32.
The gum was our womb. At six months the first of us, the two lower central incisors - You call them your front teeth - began to push their way upward. My baby version came along at 18 months and the second molars, the last baby teeth, at 24 months.
The first permanent teeth - the six-year molars - made their appearance back of all your baby teeth. These molars allowed you to chew while your body absorbed the roots of your baby teeth, causing them to loosen and make way for other permanent teeth. I came along when you where 12. The last, the wisdom teeth, didn't appear until you where 18.
Look at my structure. I'm quite a piece of engineering. My part that protrudes from the gum has a "skin" of enamel. Although it contains some organic-living-material, it is mainly calcium phosphate. My enamel consists of tiny hexagonal rods, something like bundles of pencils standing on end. It would take 100 of them to bulk as large as a hair. Since my enamel contains no nerves, it is insensitive to pain and is tough enough to stand the ferocious pressures of chewing.
Under my enamel comes the dentine, which is related to bone. Tooth sensitivity begins here. Under the dentine lies my heartland, the pulp, a relatively soft material containing nerves, blood vessels and cells that radiate into the minute tubules of the dentine. The whole tooth structure sits in a tailor-made socket in the jaw, anchored by cementum, a bony tissue, and thousands of fibers. Instead of being an integral part of your jawbone, we are more like plants growing in a flowerpot, rooted according to our jobs. A single root is enough for the cutters up front and me (a tearer of meat and tough food). The heavy-duty grinders farther back may need as many as three for support.
It's no news to you that teeth cause trouble! You have already lost four of us, and more are threatened. (Some people have lost ten by the age of 40.) Had they cared for us properly this wouldn't have happened. I know that you brush regularly and use mouthwash. You think your mouth is clean. Actually, it is a massive zoo of microbes, and there is little you can do to eliminate them.
For much of your life the great enemy was decay, caused by interaction between bacteria and food particles in the mouth. Debris collects in the crevices on teeth. Your dentist calls this plaque, and usually it's invisible. Living bacteria in plaque ferment foods, producing acid. In its turn, the acid dissolves enamel, allowing bacteria to invade the inner structure.
There is another mode of entrance. The enamel in your teeth may have minute fissures that bacteria can slip into and start the decay process under the enamel. X rays can spot this hidden decay.
The decay rate slows after age 35. The big thing for you to watch for now is periodontal disease, which strikes below the gum line. Here again, plaque is the major culprit. In time, invisible plaque picks up minerals from the saliva to become tartar - which is hard and jagged. Either tartar or plaque can wedge the gum away from the teeth, providing little pockets where food and bacteria lodge. All sorts of misery can result. Gums can become inflamed and bleed. Or bacteria can attack the softer part of the tooth normally protected by gum. Let this continue and pus pockets will form, destroying our attachment to the jaw. At this point it's very likely good-bye for us. At your age, most of your serious tooth troubles trace to this process.
If your parents had your teeth straightened when you where young, you wouldn't have had malocclusion, another cause of periodontal disease. Malocclusion means that one of us in the upper jaw doesn't mesh properly with our opposite number below. Thus one tooth works while the other one idles and gets no stimulation in its root area. The gum around the idle one falls away, bacteria invade, pus pockets form and the loosening process begins.