Those of us who are of a certain age will recall the Chiffon Margarine commercials wherein the punch line was, "It's not nice to fool Mother Nature!" The primitive special effects that followed are positively charming by today's standards:
http://www.youtube.com/watch?v=LLrTPrp-fW8
Well, when it comes to the bone that supports our teeth in our jaws, I'm tempted to say that there's a design flaw, but it's "not nice to criticize Mother Nature"! Still, you need to know what's in the maintenance manual for your body, and since a smile with gums on the proper yard line is such an important asset these days, let's talk about dental recession and the health of gums and bone.
Some of us have relatively thick, flat gums and some of us have thinner, more scalloped gums- all genetically determined. The above image shows what many consider the most esthetic type of gums in a smile, and yet these are also the most delicate. There is some recession in this photo, yes, and what's more, we can almost see through the gums to the underlying roots. The gums are thin enough as to be almost transparent, and the bone to the direct outside of the teeth is very thin indeed. This is bundle bone, which is dense bone and does not have an inner blood supply. All of the oxygen and nutrients to the bone at the direct outside of our teeth comes from the gums and also from the ligament on the tooth root, so it's very delicate.
If we look at a dental CAT scan that shows the cross section of bone in the right way, we can get an idea of how thin the bone on the outside of our teeth is compared to the bone inside, on our palate or towards our tongue:
What does this all mean? What is the effect of very thin bundle bone in this area of our jaws? Well, this bone and the gums that lay over it are both very prone to running away- recession- at the first sign of trouble. Factors that can lead to our bone and gums receding include:
-Teeth erupting, when we're kids, too far to the outside of the dental arch, away from the supporting bone. Teeth usually migrate inwards in response to pressure from the muscles of the mouth and face, or perhaps they are guided in by an orthodontist, but the damage is done since there was essentially no bone to the outside of the tooth to begin with. It doesn't grow back as they shift to a better position either.
-Orthodontists moving teeth too far off the bony base (they are trained not to do this intentionally, but many situations are very complex and involve trade-offs among various factors), or even during the process of guiding malpositioned teeth back into better alignment, the outer bundle bone may recede. In some cases palatal expanders can avoid this complication in the upper jaw by doing more than tipping teeth towards the cheeks- expanders can actually guide the growth of the palate bones themselves, which in turn keeps the bundle bone intact.
-Gum disease is certainly a major factor which can attack this bone and make it recede. Periodontal, or gum, disease is to be avoided at all costs, and can usually be controlled if diagnosed and treated early.
-Excessive grinding of the teeth, particularly at night. Either the tops of the teeth wear away much faster than average, or the stress goes into the body of the tooth and recession and chipping at the neck result. Night guards (also called "bruxing appliances") can significantly reduce the damaging effects of heavy grinding.
-Brushing too hard. This is over-rated as a cause of recession, though. Use warm water to brush, especially in winter- toothbrush bristles stiffen when they are cold. And don't scrub too hard.
-Failing teeth, teeth with fractures or teeth with severe decay. In most cases the chronic inflammation and, in later stages, infection associated with such teeth causes major destruction of the outer bundle bone. This situation creates challenges as we plan implant replacement of failing teeth.
It is possible to graft gum tissue over areas of recession (I've had two of these procedures myself). And if there are notches in the tooth at the gumline- these are called abfractions- we can bond restorations that fill in the notch, reduce sensitivity and protect the root canal inside.
In reading the current dental research on these challenges, what strikes me is the realization that even with all out tech, we still cannot replace the entire attachment apparatus that holds our teeth in place, meaning bone and gums. We can increase the amount of gum tissue, we can repair and restore notches, we can even do remarkable things to treat gum disease, using bone grafting materials to stimulate new bone growth. But we cannot (yet) induce the entire complex of gums and bone to grow back wholesale to replace tissues lost to trauma, gum disease or general recession. In time, with improvements in technology, this should become possible.
The good news is that for now, grafting with gum tissue only, and not bone, is remarkably stable and can accomplish both an improvement in appearance and also a protection against worsening gum recession over time.
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