Dr. Jahn explains the role and function of the jaw and the problems that can be caused by chronic tension. Read on to gain a deeper understanding of jaw tension and ways to mitigate it.
The craft of singing involves (among many other things!) learning to selectively relax some muscles while contracting others. Muscle tension anywhere in the body creates a problem, and nowhere more so than in the area of the vocal tract. And the strongest muscles in this area are those that close the jaw. When we bite down, our molars can exert a force of 70 lbs per square inch. Of the many muscles that are activated during singing, those of the jaw and the tongue are by far the strongest and, not coincidentally, are the most problematic for singers.
The jaw is hinged on both sides in front of both ears, forming what is conventionally referred to as the TMJ—the temporomandibular joint. The joint consists of a ball-shaped head on the jaw, which swivels and slides against the side of the skull. This movement corresponds to opening and closing the mouth (swiveling) and chewing with your molars (sliding). You can feel the area in front of your ears—and even better by placing your little fingers, facing forwards, in both ear canals, while opening and closing your mouth.
How does the jaw do its work? Under normal circumstances we eat by biting the food with our incisors, the jaw opening and closing like a hinge. We then move the food backward onto the top of the tongue. The tongue humps up, pushing the food to either side, to the molars. The molars now grind up the food (the jaw now in a sliding motion). The ground-up food is then pushed back toward the middle by the cheek muscles. The tongue now humps up, and, like a piston, pushes the food backward to begin the oral phase of swallowing.
Jaw, teeth, cheeks, and tongue work together smoothly, in a reflexive sequence. Since the main function of the jaw is chewing and clenching the teeth against resistance, the closing muscles are far stronger than those that open the mouth. Normally we do this voluntarily, with purpose, exerting intermittent pressure on the TM joints.
Persistent tension in the jaw develops when we chew incorrectly or when we clench or grind persistently. While the muscles involved for these two activities are different (clenching with the temporalis and grinding with the pterygoid muscles), the effect on the jaw, teeth, and TM joints is similar. Under normal circumstances the food should be distributed to molars on both sides, and the pressure of the bite and the grind exerted equally on both TM joints.
However, it turns out that most of us have a favorite chewing side! This is by habit, and most of us don’t even think about it. It may have started years ago, because you had a sore tooth on one side. It could also have begun after dental work, if the occlusion became changed or uneven or a filling on one side was left too high. In any case, the work of “food processing” is a situation like this is asymmetrically distributed, and the pressure transmitted to the TM joints is unequal.
Chewing is normally intermittent, and the jaw muscles have some time to relax. Clenching and grinding (known as bruxism), however, causes persistent tension in the jaw muscles as well as strain on the TM joint. There are numerous causes for bruxism. Some, such as allergic itching in the back of the throat, are treatable. In many cases, however, it reflects stress and tension: you grit your teeth in the face of adversity! In a majority of cases, however, it occurs at night while we sleep, and the only symptom is a sore jaw upon awakening (as well as possible complaints from your bed partner!).
Persistent bruxism, in addition to heightening muscle tension in the jaws, can result in abnormal wear patterns on the teeth and inflammation (and eventual damage) to the TM joints. Even in the absence of grinding, some habitually hold their jaw in a tensed position, unable to allow the muscles to fully relax.
From the singer’s point of view, chronic tension in the jaw muscles limits opening the mouth during singing. In addition to possibly decreasing the volume of sound, it can also change the quality of the voice, since the resonant qualities of the oral cavity for vowels are subtly altered.
More importantly, however, elevated muscle tension in the jaws has an adverse effect the tension of the muscles in the neck and the larynx. The position of the larynx in the neck is determined by two sets of muscles, the elevators and the depressors. To lower the larynx during trained singing, the laryngeal depressors must take charge. This is important, since it vertically expands the hypopharynx and increases the resonating space. This not only makes the voice louder but also has a positive effect on the overtones that determine vocal quality and color. However, the laryngeal elevators are stronger than the depressors and, if general muscle tension in this area is increased due to abnormal jaw tension, the larynx will tend to rise. This not only decreases vocal power and resonance but can also lead to increased muscling, as the singer tries to compensate.
In addition to muscle tension, which causes discomfort on opening and closing the jaw and even tenderness over the sides of the head, chronic bruxism can, over time, damage the TM joints. If you put your fingers over these areas and, on opening the jaw, you feel tenderness over the joint, you have a problem. If you can actually feel a click or grinding on either side, this is a sign of structural damage to the joint.
There are many ways to manage jaw tension and to prevent its effects on the voice as well as the structures involved. First, some common sense steps. Have your dentist check your teeth for any abnormal wear. These include changes in the shapes of the incisors or the molars, depending on whether the force of bruxism is exerted in the front or the back. When you eat, try to consciously chew your food on both sides. When eating something firm, like apples, “preprocess” your food in the front, using incisors and premolars, since the farther back you chew, the more the jaw needs to open, putting the muscles at a mechanical disadvantage and straining the TM joint. Eat that apple in small, rather than big, bites.
Avoiding chewing gum is also common sense, especially large wads with a firmer consistency. If you feel tension, drop the jaw (like you learn to do when beginning voice lessons), letting it go slack. Also move the jaw side to side with the mouth open, to stretch and relax the muscles. The key to optimal singing, at least from the mechanical point of view, is to gain awareness of muscle tension in different parts of the vocal tract—whether jaw, tongue or larynx—and then to “actively relax” the area.
Like many functional disorders, bruxism is often the result of other issues, and management of jaw tension can be complex, involving muscle relaxants, Botox, and even psychotherapy. But even if you don’t experience any obvious signs of jaw tension—such as sore jaws in the morning, pain or tenderness over the TM joints, or limitation of mouth opening—you should consider lesser degrees of jaw tension as a possible culprit when it comes to muscle tension affecting your singing.
And a final word, about oral appliances. These are devices that you wear over the teeth at night to reduce clenching and grinding. They are custom made and expensive, although some can be purchased “one size fits all” online. Their main benefit is to prevent tooth damage, by protecting your upper and lower teeth from one another. Appliances can also change the jaw position and can reduce the force of the clench. They do not, however, stop clenching and grinding, and we have seen many patients who, over time, chew through their oral appliances! The other problem, with appliances that move the lower jaw forward, is the increased strain on the TM joint caused by this displacement. So, while such oral appliances help, they are not the cure-all and certainly do not eliminate the vocal consequences of increased muscle tension in the jaw.
