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Clenching & Bruxing

Why do I grind my teeth at night?

Experts estimate that over one third of all adults display parafunctional (other that eating) habits with their teeth. These habits include nail biting, thumb sucking, holding a toothpick between the teeth for long periods, as well as the more common clenching or bruxing.

Clenching is when a person holds the teeth together when he is at rest. Bruxing is when a person grinds the teeth when he is at rest. The resting position for the jaws in humans is not closed, it is actually about 4mm (1/8 inch) open. You can check to see if the resting position for your jaws is open or closed by taking notice next time you are relaxing whether your teeth are closed or slightly open.

Experts estimate the average time a person has tooth contact is only about 6 minutes a day. The rest of the time the teeth are not touching each other. Most of the contact time comes from when a person swallows and the upper and lower teeth touch for a very brief period. Even when we eat, the involuntary protective mechanisms of the body act to keep the teeth from banging together except with the most forceful chewing.

A person who grinds or clenches may be grinding or clenching either during waking hours or while sleeping or both. As you might have gathered, grinding or clenching causes damage. Bruxing (grinding) causes damage to the joint, but most of the obvious damage is to the teeth. They get worn away quickly due to the long contact time and the excessive forces involved. Think of it this way, if 6 minutes a day is the normal time teeth are in contact, and a person bruxes (grinds) for one hour every day, each year that person will cause eleven years of wear on the teeth (one year of normal wear, and 60 minutes/6 minutes per day=10 years of wear from grinding). Teeth are designed to last a lifetime of 75-100 years or so. Ten years of grinding just one hour a day results in more than one entire lifetime of normal wear to the teeth. Clenching involves holding the teeth together without moving. The teeth are not worn away from clenching, but damage to the joint results due to excessive force being placed on the joint structures for long periods of time. Joint structures are progressively crushed. Both clenching and bruxing can cause also pain in the muscles that move the jaw.

Children who clench or brux are a different matter entirely. While clenching and bruxing are behaviours to be avoided for adults, among children clenching and bruxing nearly always indicate that the child is in a period of active growth of the jaws. As the jaws grow, the teeth in a child do not always have a bite that provides even contact for the teeth. The body acts to even out biting pressure over all the teeth. The only way available for the body to even out the bite is to grind down the high teeth. The saving grace in children's teeth is that the period of clenching or bruxing does not go on very long. As soon as all the teeth are erupted, the clenching or bruxing nearly always stops.

Daytime bruxers or clenchers can control the behaviour by recognizing that they are doing it and substituting something like chewing gum in its place. Controlling nighttime bruxing or clenching is more complicated. They cannot control the behaviour themselves. A splint (night guard) can be made by the dentist to stop the wear on the teeth while the patient sleeps. Often a nighttime clencher or bruxer is unaware of the habit. Others in the house often are aware of bruxism due to the squeaking noise the teeth make when very forceful bruxism occurs while sleeping. Forces as high as 260 pounds are commonly exerted on the teeth when nighttime bruxism occurs. Muscle pain in the muscles that move the jaw are often the patient's first indication they are clenching or bruxing. The pain is usually concentrated behind the eye about 1-1/2 inches on the side of the face which can radiate back over the ear, and at the angle of the jaw. If your teeth are worn down, the muscles just described hurt sometimes, or people complain about squeaking coming from your jaw when you sleep, ask your dentist about clenching and bruxing.

- This article was written by Dr. Mike Christensen and published in the Daily Miner and News, and Enterprise. Local Kenora News Publicatons (1998-2006)

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