We usually take it for granted that kids’ teeth don’t always come in straight and aligned. The prospect of a kid needing orthodontic treatment is one all parents are aware of. Estimates are that between 50% and 70% of American kids will, in fact, wear braces before adulthood. It’s safe to say that not all kids who should get have orthodontic treatment actually get it. Thus, if all kids who needed braces got them, those estimates would be even higher. In recent years orthodontists are treating more adults than ever before. Some, perhaps most of these patients are making up for lost time. They needed braces as kids, but for one reason or another didn’t get them. However, adult teeth shifting is more common than you might realize. An adult who didn’t need braces as a kid can develop that need later in life.
Surprised by this fact of adult teeth shifting? After all, adults are supposed to be done with growing and developing. Adults teeth are strongly anchored in the jawbones. It’s hard enough moving them intentionally, with braces! How is it they can move all by themselves?
Well, there are a number of ways. Several causes, in fact, of adult teeth shifting. We’ll get to these, but first, let’s review some of the basics. It’ll help to be mindful of what holds teeth in place, and what happens when we move them with braces. It’ll then be easier to understand how teeth can move “by themselves”.
TEETH AND BONE
There are four types of teeth: incisors, canines, premolars, and molars. Their structures are different, of course. The ways they anchor in the jaw bones, though, are essentially the same. They’re all anchored in sockets in the bone. They’re all secured in those sockets in the same way. The cementum is a connective tissue that bonds a tooth to the gums and jaw bone. Exactly what the name implies! The cementum’s grip is reinforced by the periodontal ligament.
Hence, the task of orthodontic treatment is to move the root of the teeth to new locations in the bone. Or, sometimes, to change the position of a tooth in the same location. Either way, the hard bone, the cementum, and the periodontal ligament resist movement.
Moving a tooth with braces involves what’s called remodeling of bone. Destruction and construction.
Suppose we want to move a front tooth to the left, to close a gap. The braces, then, apply steady pressure to the right side of the tooth, pushing it leftwards. The left side of the tooth’s root, therefore, is pressed against the left side of the bone socket the tooth’s anchored in.
This pressure has several effects. One is reduced blood flow to the area under pressure. You can see this effect by pressing with your fingertip on the inside of your forearm. When you lift your finger, the spot you pressed on is white-ish. Your fingertip pressure had reduced blood flow to that spot. This reduction in blood flow to the left side of the tooth socket means that less oxygen gets there. This condition of hypoxia, along with other effects of the pressure, results in bone resorption. That is, cell death in the “squeezed” area. The bone basically dissolves. It’s no longer hard. Resorption, then, makes it possible for the tooth to move in its direction.
On the other side of the tooth, the opposite is happening. Know the saying ‘nature abhors a vacuum”? Well, our bodies don’t like loose teeth. As the tooth moves through the dissolving bone to the left, the jaw builds new bone on the right to fill in the gap. Our bodies make every effort to keep teeth securely and tightly anchored in the jaw bones.
Some of the details of this are still just theories. What we do know, though, is that it works. We know how much pressure is best, and how to apply it, direct it, and maintain it. We get the results we want.
KIDS VS. ADULTS
It should now be easy to see why orthodontists recommend early treatment of orthodontic issues in kids. They’re still growing and developing. Their bodies are in changing mode. Changing’s what kids do. It’s easier to move their teeth, and their jawbones adapt readily. Ironically, these are also the factors that permit kids’ orthodontic problems to develop so readily: growth and development.
You might think, then, that reaching adulthood means orthodontic issues can’t any longer develop. After all, growth and development are over. Everything’s fixed in place, isn’t it? Changes from that point are just plain old getting older.
But no. If only it were so.
ADULT TEETH SHIFTING?
The American Association of Orthodontists (AAO) states that human teeth can shift and move naturally over a person’s entire lifetime. As a matter of fact, what’s called mesial drift appears to be a regular feature of the aging process. Our teeth slowly drift toward the front of our mouths as we age. Most researchers think the cause is normal wear and tear due to chewing. The (very powerful!) forces of chewing cause the sides of neighboring teeth to rub against each other. This wears down the enamel. Here, again, our bodies don’t like the tiny gaps that result. Teeth shift forward to close these gaps.
Mesial drift can be and is promoted by other factors besides the normal pressures of chewing. Some of these are behind the other was adults’ teeth move out of alignment. Anything that changes the shape of a tooth, for example, can result in movement. Wearing away of the enamel, say, by grinding or clenching teeth, can do it. When our top and bottom teeth don’t fit together as they used to, it stimulates movement. As if the teeth are trying to re-establish the good fit. Just to make things interesting, we know now that sleeping on your stomach promotes tooth movement. So, too, does, resting your chin on your hands while staring at your computer screen!
This lifelong potential for movement, incidentally, is why orthodontists prescribe retainers after the active phase of treatment. Whatever conditions originally led to misalignment can still be active.
RISKS IN ADULT TEETH SHIFTING
The problem with adult teeth shifting is that there can be consequences more serious than minor cosmetics. There can be a cascade, a chain reaction of problems leading to tooth loss, among other things. Moreover, when adults’ teeth shift, it can be a sign of serious underlying issues such as periodontal disease.
What this all boils down to is the need to pay attention to tooth alignment in adulthood. A person whose teeth were perfectly aligned at age 25 can find that situation changed 5 years, 10 years, or 25 years later. Any change from perfect alignment is potentially problematic.
YOU, YOUR DENTIST, AND YOUR ORTHODONTIST
Unless an adult is already an orthodontist’s patient, that’s not where detection of adult teeth shifting is going to happen. A dentist may notice it, especially if the patient’s been getting regular checkups with him or her for some time. Or, conversely, if the tooth movement’s due to dental problems like gum disease or a broken tooth.
In the final analysis, we adults have the first line of responsibility. Our tongues are incredibly sensitive “feelers” of the environment inside our mouths. The oral cavity, in general, is very sensitive. We’re well able to detect even tiny changes. We often find our tongues “playing” with an area that’s changed. The trick, so to speak, is to act on it when we feel something’s different in there. Your general dentist is probably the right starting point in most cases. Your Lake Worth orthodontist, should you need him, will want the general dentist to have gotten a grip on any non-orthodontic issues. The important thing is if you feel something, say something!