The jaw system is composed of three major interactive components. They are:
• The temporomandibular (jaw) joints
• The jaw muscles that move and control the jaw, as well as loading of the jaw
• The teeth, through which that load is transmitted
In other joint systems of the body, there are only two interactive components; the joint and the muscles that move the joint. There is no other joint system in the body that has a component similar to the teeth that can so profoundly affect the function of the joints and the muscles of the system. This is why the fit of the teeth (the bite) is so important in the function of this joint system, and especially when there is pain in the jaw, which we refer to as temporomandibular disorders, or more commonly referred to as “TMJ”.
When you, or anyone who has most of their teeth, close your mouth, you will always close with a high degree of precision in one position — where your teeth fit together best. Regardless of how good or bad the fit may be, that is where you will always close. This closure to a precise position is controlled by a highly sophisticated physiologic mechanism called a muscular engram. It is sometime referred to as “muscle memory”. It is involved in all coordinated muscle functions, as would occur when running up a flight of stairs or riding a bicycle.
Once learned, this muscle pattern becomes automatic and can be relied on to repeat predictably when needed, without your having to think about it. With jaw closure, it would be apparent if I were to ask you to tap your teeth together repeatedly very quickly. You always close precisely in one position, as dictated by how the teeth fit. But it isn’t about a mechanical fit of the teeth – it’s about the muscles having learned, have become programmed, just where to close by the fit of the teeth. It is muscle memory at work.
• Jaw Position
If this programmed closure to a precise fit of the teeth were not true, your teeth would be constantly clashing when you talk or chew. Because this closure position is so precise and automatic, you probably take for granted that this is the “right” place for your jaw to close. But because the bite always determines the jaw closure position, it is also what determines the position of the jaw joints; the position of the condyle (ball) in the fossa (socket). There is a hierarchy in the jaw system and the fit of the teeth always wins over the jaw joints. And in people who are having pain or functional problems with their jaw, this effect on the jaw joints can be a major contributing factor.
Jaw function requires both stability of the joints and relaxed muscle function to work efficiently and stress-free. A jaw position where the teeth fit together best can be a somewhat different position than the position in which the jaw joints are stable and where the jaw muscle are most able to be relaxed. When there is a conflict between these two position, and the joints are not in the most stable position, the muscles that move the jaw tend to become tight, and are not relaxed and are, therefore, not able to work in a coordinated manner. So the fit of the teeth can have a profound effect on both the function of the jaw joints and on the muscles that move the jaw.
• Fit of the Back Teeth
What may appear to you to be a normal bite (because you have lived with it more or less successfully most of your life) can contribute to joint pain and muscular tension in several ways. Teeth that seem to fit together well in the back of your mouth often do not support the jaw appropriately, even when all teeth are present. In addition to the need for the jaw to be in the correct position, the way the individual teeth come together in the back has a lot to do with how relaxed the jaw muscles will be. Optimum, solid tooth contacts are often missing in a natural bite, even when all teeth are present.
• Function of the Front Teeth
The front teeth also have an important role to play in a bite that functions well. In a good bite, or occlusion, there should be a certain amount of overlap of the front teeth. When you slide your jaw to the side or forward, this “overbite’ of the front teeth should be the only place in your mouth where the teeth touch and the back teeth should separate. The amount of overbite makes sliding the jaw quite easy, requiring very little muscle effort.
If this ideal amount of overbite is not present, then the back teeth will tend to drag during jaw movements or when you grind your teeth. On the other hand, the overbite can be too deep or tight. This can hinder normal jaw movement and may also contribute to maintaining your lower jaw in an unfavorable position. So, very simply, the overbite can be too little or too much. When it is just right, it contributes to the appropriate function of the jaw mechanism.
• Problems Resulting From a Bad Bite
If clenching and/or grinding of your teeth has contributed to pain in the jaw, a “bad bite” can serve to perpetuate clenching or grinding. If there is not enough overbite, the back teeth will rub, contributing to increased activity of the jaw muscles. If the overbite is too deep, steep, or tight, jaw movement is more difficult and, again, the jaw muscles have to work too hard. This type of “deep” overbite of the front teeth, particularly if these teeth are straight up and down, is like having the lower jaw in a straight jacket. The muscles don’t tolerate this restriction and the result can be more too grinding in an attempt to “break out” of this restriction. Tooth clenching and grinding leads to over use of jaw muscles, leading to muscle pain and headaches.
• Patient Self-Assessment of Dental Occlusion (Bite)
In my office I routinely ask new patients to tell me how their bite actually feels to them. Is closure of your back teeth easy and comfortable? Do your back teeth touch on both sides? Do they contact equally on both sides? With the back teeth together, do the front teeth touch? Which touches more heavily, front or back? Then I ask the patient to choose one or more of the following words to describe how their bite feels; comfortable, solid, even, uneven, uncomfortable, strained, painful. The responses to these questions will tell me a lot about whether the bite is an issue with the patient’s jaw problem. If there is clicking or popping of the jaw joints, these responses are even more meaningful.
• Bite Problems With Abnormal Jaw Joints
When the jaw joints have lost their normal structural integrity, as indicated by clicking and popping, the type of deep bite problem described above can be even more irritating and problematic. Fully normal joints should not hurt. When there has been a structural change in your jaw joints, and when there is pain coming from injured and inflamed tissues within the joints, the jaw position that is dictated by your bite may keep these tissues irritated with just normal day-to-day activities, such as eating and talking. These irritated and painful tissues within the jaw joint contribute to tight muscles and symptoms such as headache and jaw ache through a normal response of the muscles to this pain, referred to as reflex muscle splinting. This response can be seen with any moveable joint.
• Bad Bite Due to Missing Teeth
When there has been a loss of back teeth, this may also contribute to inadequate support for the jaw, leading to more muscular tension and pressure on the jaw joints. This can be true even if these missing teeth have been replaced by partial or full dentures. Because dentures and partial dentures rest on soft gum tissue, which changes over time when it is loaded, the bite on dentures and partial will change and adequate support for the jaw can be lost, often very quickly. Today, a better option in many cases is to replace missing teeth with implants and crowns. This will assure that the bite, once corrected, will not change.
• Discovering What May Be Wrong With Your Bite
In the treatment of jaw joint and jaw muscle pain, one of the primary reasons for wearing an oral appliance or “splint” is to temporarily eliminate any effect from the bite that may be contributing to the pain. The appliance should mask the detrimental effects of the natural bite and provide a more ideal bite, temporarily on plastic, which will allow the jaw to close in a relaxed position. It will also provide solid tooth contacts (which are often missing in a natural bite) and it allows the jaw freedom to move easily.
Each of these design elements in the oral appliance contribute to relaxation of the jaw muscles. It also eliminates the effect of bite closure on joint position and allows the jaw muscles to position the joints in a more favorable position. Over time, this allows me to determine where the jaw should close. This corrected bite position may be different from the position that is determined by where the teeth fit best.
Frequently, when the muscles are permitted to achieve full relaxation, clenching and/or grinding of the teeth will be significantly reduced or even eliminated. The ultimate objective, after your pain and other symptoms have been eliminated, is to provide a bite that allows the jaw muscles and the jaw joints to function in as relaxed and comfortable a position as is possible. This harmonious integration of the three components of the jaw system, the teeth, the muscle , and the jaw joints, will minimize the likelihood that you will have a return of this problem in the future.
• Treatment of Your Pain
The initial treatment is designed to bring your symptoms under control and to achieve a stable and relaxed position for your jaw. If these two objectives are achieved, we will then be able to carefully evaluate how the teeth come together in the corrected jaw position, the position that your jaw has achieved as a result of wearing the appliance. This is done by mounting models of your teeth on a jaw-simulating instrument, called an articulator. With these mounted models of your teeth I am able to determine very precisely if you will require a correction of your bite and, if so, exactly what that will require. I can then make recommendations to you about this bite correction.
• Night Time vs. Full Time Appliance Wear
Sometimes patient who have had previous treatment have been told to wear an oral appliance only at night, when sleeping. Such an appliance is usually referred to as a “night guard” or “bruxism splint”. An appliance of this type may reduce, and sometimes eliminate, the most obvious symptoms, especially if the problem is less complex or the pain has not been long-standing.
But often more difficult problems will not respond adequately to just night time wear of an appliance. With only night-time wear of the appliance, the jaw muscles are never able to reach a state of optimum relaxation because the appliance is taken out during the day and the natural bite is reintroduced. When an appliance is used in this manner, it should be thought of as being like a crutch, helping you limp through life with a chronic condition. An approach of this kind is not definitively addressing one of the major underlying contributors to the problem, your bite.
For most patients, my personal preference is to achieve a more definitive result than can be achieved by having the patient wear the oral appliance only during sleep. However, there are certain situations where that may not be practical or desirable or where night-time wear is actually preferable. I welcome the opportunity to discuss this with you.
