Bruxism means grinding the teeth and is considered a parafunctional habit, or one that is not within the range of what the human mouth was "designed" for. Specifically, normal functions of our mouths would be things like chewing, speaking, and differentiating between a refined Tanzanian Peaberry and a rare Kopi Luwak civet coffee from East Timor.
Grinding our jaws heavily back and forth, especially during sleep, however, is not considered "normal" use of our teeth and, when we start doing it consistently, one of three things in our bodies tends to get damaged.
The first possibility involves the ligaments that hold our teeth into our jaws. Yes, it's not just teeth and bones- there's a periodontal ligament (PDL) that attaches one to the other. Under greater than normal stress, especially back-and-forth forces, the PDL gets inflamed and widens considerably.
Using X-rays of lower front teeth to demostrate, I have placed arrows pointing to a normal PDL. It's that fine dark line that surrounds each tooth on an X-ray:
The next image is from a patient who had prior gum disease. They are absolutely healthy and well-maintained now. I say that because gum disease causes changes to the PDL that are distinct from the changes wrought by bruxing. So in this case, we have healthy gums but prior bone loss from the gum disease some years ago. There's less bone to support the teeth, so that higher than normal forces have a greater effect on these teeth than on well-supported ones. Less bone support means more chance for mobility, and we see a widened PDL in reaction to that:
Within reason, this is considered a physiologic (adaptive), not pathologic, reaction to repetitive stress and as long as the teeth are not so loose as to cause the patient pain, this condition can persist for years without major harm. It always occurs to an extent during orthodontics, by the way. It even occurs (rarely) on teeth with full, normal bone support, where patients simply grind a lot. In some cases, a change of employment is the most effective treatment...
Adaptive mobility is nature's way of getting teeth out of harm when the forces on them are high. Regrettably, though, this is the most rare mechanism of dealing with overload. What happens far more often is:
Yes, it is astonishing how much a human being can wear down their teeth over time by bruxism. This condition is astronomically expensive to treat properly, as each and every tooth most be restored with a full crown in order to regain its normal form and function. The trouble with that approach is, if the bruxism is still going on, even our strongest porcelains are probably going to break. It'd be like buying a Bentley for $360,000 U.S. and then driving it recklessly in Rome, where motoring is more chaotic and stressful than any video game can ever hope to be.
You know, going in, that your expensive Bentley is going to get trashed.
Same with major dental reconstructions in bruxers. The best advice I can give you is: if your dentist sees early signs of wear and recommends a bruxing guard appliance to prevent further wear, go ahead and have it made and then wear it consistently at night. I know it will likely cost something like $550 plus or minus, and dental benefits, if you have them, often don't cover these devices in spite of the costs which they prevent. But you need to weigh that $550 against $30,000 or so for full mouth reconstruction at some point down the road, not to mention hours and hours in the dental chair and loss of beauty and function along the way.
The third, and potentially most serious, structure that can be damaged by bruxing is the temporomandibular joint (TMJ).
The bones of the joint and skull can be affected by degenerative changes; the potato-shaped condyle flattens, for one. Yet of most concern is the soft tissue disc that lies in between the bones. It's complex, but consists of cartilage and connective tissue and has more of its blood supply to the rear than to the front. If this becomes worn and crushed and even perforated, even in 2011 the treatment options are not good. It is, quite simply, an irreplaceable object in our bodies and preserving its health is vital to avoiding chronic, debilitating pain.
Here are some images from the DDS GP app for the iPad. The blue structure is the disc within the joint:
A simplified, but beautiful, representation of the disc in action as a patient opens. This remarkable app is here: http://www.ddsgp.com/DDSGP/Home.html
These bruxing guards, or night guards as they are often called, do a number of subtle things. One of the most important is to draw the bones apart; moving the condyle away from the base of the skull. This provides increased blood supply and directly reduces the crushing forces on the delicate disc, especially during grinding at night, when the patient is asleep and unaware. The disc can be maintained in a greater state of health in this way than if no device is worn.
Many of these decisions come down to economics; I understand that. Still, we have to look ourselves in the eye and realize that human beings are much better at assessing short-term risk than long-term risk. There are many smokers out there who would never stick their wet finger in an electric socket, and even many who are afraid to fly.
The bottom line is that if there is solid evidence of teeth wearing down, or painful TMJ symptoms, or, to a lesser extent, tooth mobility from grinding, a bruxing guard appliance is worth its cost when weighed against the cost of a major reconstruction in the future, and a steadily increasing damage to the appearance and function of your precious smile all along the way.
(Here are DDS GP images of a bruxing guard):