The Front Flat Plate Appliance
SUMMARY - The front flat bite plate appliance has short, medium, and long-term effects. From the first night it is worn, it reduces the strength of nocturnal bruxism (clenching and grinding) by about half. Over the course of weeks, it deprograms the jaw muscles so we can see if they prefer a different bite position more compatible with your body posture. Over the course of years, it redirects the forces of nocturnal bruxism axially on the front teeth to gradually reduce overbite. These effects are described in more detail below. To make the appliance comfortable, we make it as thin as possible and give it a completely passive fit, so it does not apply any pressure to teeth. To promote healthy tongue posture, we hollow out an area beneath the bite table in the front of the palate for the tip of the tongue. A temporary version, which will last for at least weeks, can be made chairside for $100.
BRUXISM - Nocturnal bruxism occurs in everybody during transitions between sleep stages, and it is more frequent and forceful during times of stress. Clenching compresses the vessels that supply circulation to the tooth pulps, causing ischemia that can make teeth temperature sensitive and eventually strangle them, requiring root canals. Grinding exacerbates gum disease by loosening the teeth like rocking a fence post. Grinding also slightly bends the teeth, which can break away little bits of enamel from just above the gumline, leaving V-shaped defects called abfractions that can trap food and cause decay or gum disease.
A front flat bite plate appliance eliminates all bruxism forces on the molars and premolars. Those teeth cannot even contact while the appliance is worn. It also reduces the bruxism forces applied to the rest of the teeth, because the jaw muscles are wired in a positive feedback loop that requires stable contacts on the back teeth before the neuromuscular reflexes will allow the jaw muscles to fire strongly, and the front bite plate prevents that "go ahead" signal. As a result, it reduces the forces of nocturnal bruxism by about half every night you wear it. In this manner, it performs the same function as Botox, without damaging the muscles that are needed for regulating facial growth; the failure of which is at the root of TMJ disorders, as explained in the ETIOLOGY files.
HEADACHES are often reduced or eliminated by the reduction in the strength of nocturnal bruxism. We still don't understand the mechanisms behind headaches, but we know that the jaw muscles control pressure on the head. In monkeys, forceful biting bends the skull. In humans, the jaw muscles are weaker, but our craniofacial skeletons are more delicate, therefore it should come as no surprise that excessive jaw muscle tension can produce enough pressure on the cranium to interfere with cranial circulation. Chewing has been shown to increase cranial circulation. In fact, the jaw muscles are such important regulators of cranial circulation that reducing their tonus often relieves headaches from unrelated sources.
DEPROGRAMMING THE BITE - The upper front flat plate contacts only the lower front 6 teeth (including the canines for stability) on a bite surface which is so smooth and flat that it allows the jaw to slide around freely, almost like ice skating. The jaw muscles can rest and exercise the mandible wherever they want. As a result, they stop automatically closing the mandible into the one place where all the back teeth fit. If they choose a new position consistently, the old position was strained. Some people feel like their jaw has been freed. Others feel like their bite has been disrupted, because their jaw muscles don’t want to bring their mandible back to its old bite position. Some people with healthy strong muscles may even have trouble finding their old bite in the morning, because their jaw muscles have become used to operating in the new more comfortable mandibular position, and they can hold that position for some time despite the teeth not fitting there. This feeling of bite disruption can be upsetting, but it's actuallly a good sign, it's an indication that your symptoms can be relieved by improving your bite.
The average TMJ disorder patient requires a few weeks of nightly flat plate appliance wear to deprogram. Some patients with longstanding TMJ disorders and weak jaw muscles may require much longer to deprogram, and they may also need bite stabilization and supportive therapies such as exercise and massage before the jaw muscles can demonstrate a healthy unstrained jaw closing trajectory.
The height of the front flat bite plate determines the amount of stretch it applies to the jaw closing muscles. If the bite plate starts out too tall, it may be difficult to tolerate for 8 hours at first due to the compressive forces generated by passive stretch of the jaw closing muscles. Then it can be easily lowered in a short appointment, or you can start out with shorter wearing times. If the bite plate starts out too short, it may not provide enough jaw muscle stretching to eliminate all the symptoms; and its height can be increased during an appointment for a small lab fee.
WHAT TO EXPECT - In the morning, when you wake up with the appliance still in your mouth and your jaw muscles deprogrammed, your mandible swings open and closed along a trajectory that fits the light steady background tensions of your postural system. If that postural jaw closing trajectory brings your mandible directly into your natural bite, the location of your natural bite is probably healthy, although its range of motion could still be restricted. If that postural jaw closing trajectory brings your mandible into contact with only one or two teeth before sliding backward or sideways on those teeth into your full natural bite, those teeth are the cause of your bite strain, and identifying the surfaces that produce the slide is the key to improving your bite.
POSTURE – If your postural system is healthy, your mandibular posture should be made to fit your head posture. The process may require adjusting your bite, because the position of your mandible in its full bite controls its postural position. If your postural system is strained, your mandibular and spinal posture should be improved together, and deprogramming your jaw muscles can provide a window of time for postural work that also realigns your mandible before locking in that mandibular posture by means of permanent dental work, such as crowns.
REDUCING OVERBITE - The vertical overlap of the front teeth, the overbite, can cause TMJ disorders and postural problems by preventing the natural mandibular advancement needed to reduce resistance in our airways with age. Our jaws are programmed to compensate for progressive weakness in the respiratory muscles during adulthood by slowly advancing the mandible, but this natural mandibular advancement can be blocked by deep overbites or steeply interdigitating teeth.
When the advancement of the mandible is blocked, its growth usually gets redirected down and back into the space needed for the pharyngeal airway, where it can cause sleep apnea. In people with stronger jaw muscles, the mandibular corpus is prevented from moving downward, but it is still usually locked back behind a deep anterior overbite.
The front flat plate appliance facilitates advancement of the mandible by reducing restrictive overbites. It uses the forces of nocturnal bruxism to push upward on the upper front teeth and downward on the lower front teeth until their overlap diminishes far enough to allow the natural advancement of the mandible with age. The effect is to gradually shorten the front teeth by intruding them (pushing them back into their basal bones) while lengthening the back teeth by allowing them to get taller and extrude from their basal bones due to their natural eruption process. In this manner, the appliance uses the forces generated by your nocturnal bruxism to perform the orthodontics you need. It only reduces overbite slowly, at an average rate of ½ mm per year; but that rate is more than adequate to accommodate the slow mandibular advancement of adulthood.
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 relative heights of the front and back portions of the appliance. When the front bite plate has worn down far enough, the back teeth begin to contact, and the appliance then becomes a stabilization appliance. At that point, if the muscle symptoms recur, the stability of the appliance can be increased by adding acrylic to the low spots, the natural bite can be stabilized, or the muscles can be rehabilitated with physical therapy, exercises, and stretches.
In some people, the natural overbite is already very small, and further reduction could separate the front teeth, causing an open bite that makes it difficult to incise. Therefore, to prevent further reduction of the overbite, they need to wear a full arch flat plate appliance rather than a front flat plate appliance.