Bite Point

Bruxism: Something's Gotta Give

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:

 
Wear.

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):

 
 
 

Dental Implant Support For Dentures

Less Americans are "edentulous" (have no teeth left at all) and wear full dentures than ever before in our history, yet there are still millions of denture wearers in our country and they face several important challenges in terms of dental health and overall nutrition.

One key point that is often overlooked is that the jawbones in the areas where the teeth were, both upper and lower, tend to dissolve back (the proper term is "resorb") to a lower, flatter level.  In the most severe cases the upper jaw can be eggshell-thin over the sinuses and the lower jaw can become almost as thin as a pencil.  These are the extremes, yet I have seen them in practice.

The common issue that we hear about the most is instability of dentures.  Uppers are usually less problematic than lowers in terms of stability while eating and speaking.  Upper dentures are D-shaped affairs that gain a great deal of suction across the entire palate.  Of course, this coverage to gain retention comes at the cost of blocking a portion of our sense of taste and smell, and there is an issue of bulk to be concerned with.  Still, most patients can have a stable upper denture created for them.

It's the lower denture that is extraordinarily difficult for dentists to create and, once fabricated properly, for patients to train themselves to wear and use successfully.  Think about it- you've got this little C-shaped ridge of bone with delicate tissue over it, the lips and cheeks with all their musculature on one side, and the even more muscular tongue on the other.  Now we're going to ask the patient to eat, talk, and perhaps, back when dentures were more common, sing opera with something in their mouth that is not anchored to anything in any way.  It just floats on top of the gums.  The only adhesion comes from the layer of saliva interposed between the denture base and the gums, perhaps with the addition of denture adhesive paste which has severe limitations.

No wonder in the 1800's the most expensive seats in opera houses were in the ninth row back.  The first eight rows were less desireable and as cheap as the seats in the rear, being called the "sezione protesi schiaffo".  Loosely translated, "Denture Smacking Section", due to the tendency for these prostheses to dangerously come flying out of the mouths of tenors and divas like foul balls along the third base line, back in an era when a more primitive dentistry was often unable to preserve the teeth of even the wealthy and successful in society.

What can be done nowadays to provide stability and thus improve the lives of denture wearers?

Dental implants, in two distinct varieties, can anchor upper and especially lower dentures and provide great improvements in stability and function for the patient.

The very first issue however is still about the actual fit of a denture.  If it doesn’t fit well against the tissues, even implants won’t make it fully stable.

The bite has to be adjusted well, too.  If denture teeth are worn down too much the denture might be stable at rest, but then it can move all around during chewing because the bite is randomly off kilter.

When considering implant support for dentures we can start with either a new prosthesis or a well-fitting older one, as long as the denture teeth are intact and not overly worn.

There are two implant choices.  Conventional implants are used for many things, including replacing individual teeth.  They can also be used to support dentures.  The bone still resists compressive forces when the patient bites down, but all other forces- pulling the denture off, like with sticky foods, rotation, tipping- all are resisted by the implant anchorage.  Two implants can be sufficient.  Three are amazing, because of the tripod effect.  Think about it as costs versus benefits are weighed- I've never seen a two-legged barstool.  Three legs might do, though, as long as patrons didn't drink too much.  Four implants, like four chair legs, is certainly the most stable option.  Due to cost considerations, though, three implants is often the best compromise and patients are extremely happy with the stability they provide.

Here, using a patient education model, we see the concept clearly:

 
 
 

Then there are mini-implants.  The cost of these is usually roughly less than half of conventional implants.  In the beginning of their development they were considered long-term temporary solutions, but they have evolved to the point where they are often considered as permanent as the other implants.  Most options here follow the same issues with number of implants as with conventional implants, meaning that four is rock-solid.  Patients can be very happy with two, however, providing the denture fits well.  Even two mini-implants provide dramatic increases in stability over nothing at all.

Here is a model of a mini-implant supported denture; I tried very hard to refrain to make boxing jokes about "glass jaws" but now I've gone and done it anyway:

 
 

The critical consideration in planning dental implants for denture support of course is: how much bone is left be the time we get to the point of considering this type of treatment.  Fortunately the front area of the lower jaw has no major nerves or arteries and usually provides adequate volume and density of bone to allow for excellent and predictable implant placement.  The same holds true in the upper jaw in the area to the front, forward of the sinuses.  However when either site is too compromised, there are now available numerous bone grafting procedures that can gain back enough bone to support dental implants.  This is truly remarkable technology and those patients of ours who have accepted this treatment have been unanimously happy with the results, and have deemed it worth all the effort and expense.