The Front Flat Plate Appliance


The front flat plate appliance covers all the upper teeth and contacts only the six lower front teeth on a bite surface which is so flat and smooth that it allows the lower jawbone to freely glide around in all directions and to grind or clench all night in any position the jaw muscles choose.  Within days it is frequently effective at relieving headache, facial soreness, and unexplained dental problems; because it dramatically reduces the forces used in the nightly clenching or grinding of teeth.  Over the course of weeks and months it can tell us if your bite is strained and how to improve it.  Over the course of years it can reduce overbite by redirecting the nightly clenching and grinding forces upward on the upper front teeth and downward on the lower front teeth. This appliance fits passively on the teeth and provides a dedicated space for the tip of the tongue, making it comfortable enough for long term wear.  The  cost is $900.  The front flat plate appliance is a muscle treatment rather than a joint treatment, so it is not suitable for inflamed TMJs.  It has the following three effects.   


The upper front flat plate appliance reduces the forces used in nocturnal bruxism, because the jaw muscles are unable to fire strongly unless they receive a proprioceptive "go ahead" from the neuromuscular system after it has detected multiple stable contacts between the back teeth.   Studies have shown that even just anesthetizing the back teeth can prevent the jaw muscles from being able to fire strongly.  Because the front flat plate appliance does not contact any back teeth, it reduces the forces used by the jaw muscles during nocturnal bruxism by about half. 

DENTAL PROBLEMS involving the premolars and molars are often eliminated because the appliance completely removes all bite forces from the back teeth and reduces the forces on the front teeth.  People often report relief from idiopathic (unexplained) tooth pain, temperature sensitivity, and even gum disease.  One dental problem that is largely due to the effect of clenching and grinding on the back teeth is gumline defects on the outer edges of primarily the canines and premolars.  These defects were long thought to be caused by excessive tooth brushing, a belief which created the market for soft toothbrushes that persists today.  However we now know that most of these defects result from the slight bending of the teeth which breaks out bits of the brittle enamel at the area of maximal flexure at the gumline just above the top of the socket during grinding and clenching.

HEADACHES are often relieved by reducing the forces applied during nocturnal bruxism.  We still don't understand the mechanisms behind headaches, but we know that the jaw muscles can apply powerful forces to the head.  In monkeys, forceful biting measurably bends the skull.  Human jaw muscles are not as strong, but our craniofacial skeletons are much more delicate, therefore it should come as no surprise that excessive jaw muscle tension is a frequent cause of headaches.  

NTI appliances, small plastic shells that are aggressively marketed to dentists today, also contact only the lower front teeth and thus can also reduce the forces used in nocturnal bruxism.  They sometimes relieve headaches.  However, NTI appliances place all the bruxism forces on the upper front teeth, and they can easily move or damage those teeth.


The vertical overlap of the front teeth, known as overbite, becomes a problem when it forms a barrier to the normal forward growth of the lower jawbone by creating a wall of tooth structure in front of it.  In normal facial growth, the lower jawbone elongates, pushing its front end gradually further forward under the midface over time.  When the front end of the lower jawbone cannot shift forward because it is blocked by a wall of overbite, the elongation of the lower jawbone can drive its back ends (the condyles) backward in the TMJs. In a highly lubricated joint cavity, such backward pressure can dislocate the disk like squeezing out a watermelon seed from between two fingers.  The role of the overbite in this regard is explained further in THE ROLE OF ORTHODONTICS under TMJ DISORDERS and in detail in CHAPTER 4 of the ETIOLOGY files.

The front flat plate appliance reduces overbite by redirecting the vectors of nocturnal bruxism upward on the upper front teeth and downward on the lower front teeth.  As these forces intrude the front teeth into their basal bones, the uppers and lowers are pushed vertically away from each other, decreasing the amount of overlap.  At the same time, the back teeth experience the opposite effect.  Relieved of all bite forces, they erupt towards each other and get taller.  Making the front teeth shorter and the back teeth taller reduces overbite.   Wearing the front flat bite appliance only at night reduces overbite slowly, usually at the rate of less than ½ mm per year; but that rate is more than adequate to accommodate adult facial growth, which also occurs slowly. Because the overbite will keep reducing only until the back teeth start to make contact with the appliance, the target reduction in overbite can be controlled by adjusting the height of the flat plate.  

If the overbite needs immediate reduction to relieve acute symptoms, a little enamel from the prematurely contacting teeth - usually the outer top edges of the lower front teeth or the inner surfaces of the upper front teeth, can be easily and safely ground down.  This process does not hurt the teeth in any way, because decay occurs where food gets trapped no matter how thick the enamel is there, and food rarely gets trapped on the biting edges of front teeth.  In fact drilling off some height from the lower front teeth probably does more to help them than to hurt them, because it reduces the torque that these teeth receive from biting - effectively reducing the height of a fence post so it is less easily rocked.


When bite strain is suspected as the cause of the jaw muscle tightness or ongoing TMJ damage, the upper front flat plate appliance can help identify the source of the bite strain by deprogramming the jaw muscles so they stop automatically closing the lower jawbone into the one place where all the back teeth fit.  The plate they strike when they bite is so smooth and flat that it allows the lower jawbone to rub all around easily without encountering any ramps or bumps - almost like ice skating.  As a result, the jaw muscles can exercise and brace the lower jawbone in any position that feels natural and comfortable for them.  To many people it feels like their jaw has been freed and can move around much more easily.  

THE TIME NEEDED to deprogram the jaw muscles depends on the health of those muscles.  Children and young people with healthy jaw muscles often deprogram overnight.  They may even have trouble finding the old strained bite in the morning after removing the flat plate appliance, because the deprogrammed jaw muscles have become used to operating in the new more comfortable lower jawbone position, and they can hold that position for some time in spite of the teeth not fitting there.  The average adult TMJ disorder patient requires days or weeks of nightly wear to deprogram.  Some patients with longstanding TMJ disorders characterized by weakened unhealthy jaw muscles may also require bite stabilization, jaw muscle exercises, stretching, physical therapy, or massage to help rehabilitate those jaw muscles before they can demonstrate a natural unstrained jaw closing trajectory.   


Keeping the bite unlocked can provide a window of time for postural work to align the jawbone with the rest of the postural system before locking in the jawbone alignment by permanent dental work such as crowns.  After the jaw muscles stop holding the lower jawbone just beneath wherever the teeth fit, the position of the lower jawbone is controlled by the same postural forces that control the resting postures of the other members of the skeleton - the passive tensions of the sheets of muscles and fascia in which they are all embedded.  If those myofascial forces change because of an improvement in posture, the natural position of the lower jawbone will change accordingly.  Stabilizing the bite in that new improved lower jawbone position will stabilize the new improved posture, just as stabilizing the bite in its old position stabilizes the old strained posture. The way the bite and posture are connected is described in non-technical language in THE ROLE OF BODY POSTURE under TMJ DISORDERS and in technical language in OCCLUSION AND BODY POSTURE under FOR DOCTORS.


In the morning, when you wake up with the appliance still in your mouth and your lower jawbone deprogrammed, your lower jawbone swings open and closed along a trajectory that fits the passive tensions of your whole postural system, and you can bring your lower jawbone to the position that feels like its center.  You can check this position in a mirror.  Then, as soon as you remove the appliance and close a little further, all your back teeth should hit together like a table with solid legs.  If you have a strained bite, you should be able to identify the tooth surfaces that strike first and then deflect your lower jawbone away from its ideal biting position and toward the old bite until it meets the other teeth. The sensation may be fleeting at first, because the jaw muscles will quickly become reprogrammed and the next closure will aim directly for your old bite. As your jaw muscles become healthier over the following weeks, the location of the initially contacting tooth or teeth should become clear, and you should be able to identify the slide in a mirror. That observation makes it easy to improve your bite, which in many cases is getting to the ultimate source of the problem.

If your lower jawbone has been displaced to one side, when you remove the appliance and bite down for the first time, you will likely see your lower jawbone shift away from the midline (where it should be) and toward the side of your TMJ that has undergone the most degeneration.  The shift of the lower jawbone is almost always toward the most advanced TMJ disorder, because the lower jawbone functions like a big triangle. When the chin shifts to one side, that is the side on which the condyle shifts backward and forces the disk to dislocate, which begins the arthritic process.  In some TMJ disorder patients, the TMJ of that side has already undergone full adaptation, and the other side may be the cause of the symptoms.

In most adults with a lower jawbone that is displaced to one side, the teeth have been forcing the lower jawbone to grow toward that side for many years, and that sideways growth has caused asymmetry in the growth of the rest of your face.   Typically, if you put a grid over a picture of your face, your chin is shifted visibly to that side, and your eye on the other side appears higher in the face.  In these cases treatment will not fully restore symmetry, because the bones have grown asymmetrically for a long time, but treatment can restore some of the symmetry and also ensure a more symmetrical subsequent adult facial growth pattern. 


Not all strained bites need correcting.  Many people can live comfortably with a slightly strained bite, especially if they can wear an oral appliance which relieves the strain all night or if they have good adaptive capacity.  If your strained bite is causing symptoms, there are a number of ways to improve it.   High spots can be drilled down, low spots can be built up, teeth can be moved, or these techniques can be combined.  The choice depends on facial height and dental conditions.

The simplest, fastest, and least expensive way to improve a strained bite is to drill down high spots known as bite interferences. When you swing your jaw closed naturally every morning after you remove the front flat plate appliance, if you notice one tooth striking before other teeth, that tooth probably constitutes what is known as a bite interference. It interferes with you achieving a healthy bite.  If you squeeze your lower jawbone closed against a bite interference, it will drive your lower jawbone backward, forward, and/or to one side until it moves away from the center and all the way to your current strained bite position.  Removing bite interferences can allow your lower jawbone to close and chew in a position that is more comfortable for your jaw muscles and TMJs.  It also slightly reduces face height, which is helpful for people with relatively long faces. 

Another way to improve a strained bite is by building up low areas.  The build-ups are produced first using composite resin to be sure the bite surface is correct before reproducing it in gold or porcelain.  The build-ups slightly increase face height, which is helpful for people with relatively short faces.

When crowns or onlays are needed anyway for structural support of teeth that have been weakened due to a filling, restoring those teeth provides a good opportunity to improve a bite.  Dentists are trained to duplicate the patients habitual bite when they perform crowns and onlays.  If that habitual bite is strained, a new improved bite can be established in composite resin and tested so that the crowns and onlays can be made to the improved bite.  A detailed discussion of the importance of the bite and the various techniques for adjusting it can be found in THE ROLE OF THE BITE under TMJ DISORDERS, and an even more detailed and technical (dental language) discussion can be found in the DENTAL OCCLUSION files under FOR DOCTORS.


If oral appliances are properly made and all the clinical judgements regarding orthopedics are correct, they should not need adjustments. However, we usually start with the simplest appliance that is likely to eliminate your problem.  If it does not completely eliminate your problem, your experience with wearing it may indicate that you need a different type of appliance or a different treatment entirely.  Some people with badly damaged jaw muscles may have difficulty adjusting to the height of the bite plate and may not be able to wear it all night for a week or two, removing it whenever they wake up during that transition period.

The front flat plate appliance is only a muscle treatment.  If it does not provide relief, you likely have a problem with one or both of your TMJs rather than just your jaw muscles, and your appliance needs to be converted to a stabilization or telescopic appliance to protect your TMJs.   There is a laboratory charge for such conversions, but it is significantly less than the cost of a new appliance.  


The front flat bite plate should last for many years.  If it wears down to the point where it is no longer effective but has not yet completely fallen apart, the lost height can be rebuilt at a one hour appointment for $250.