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August 2001
Vol. 10, No. 08,
pp 39–40, 43.
Health Perspectives
The nightly grind

Dentists and doctors explore the reasons behind nocturnal tooth grinding.

Here’s a fact to sink your teeth into: A good 8% of people in the United States grind their teeth into worn-down nubs while ostensibly resting in sleep. Called bruxism, unconscious nocturnal gnashing can disturb sufferers so much that eating becomes a problem, jaw joints grow inflamed, and sleeping partners complain that the noise is depriving them of their needed rest.

During normal chewing, the teeth and jaws generate an impressive 175 lb/sq in. of pressure. But nighttime gnashing can cause pressures on the jaw up to six times greater than normal chewing. When repeated night after night, for months or years on end, bruxism can cause an astonishing range of problems for the unconscious grinder.

The most obvious issue is premature wear on the teeth. The soft, highly refined Western diet keeps many people’s pearly whites healthy and sharp into the sixth decade and beyond. But add tooth grinding to the equation and suddenly people are subject to teeth worn down to sharp facets that wiggle in their sockets and break or chip easily. As grinding wears the enamel away, it exposes the dentin and makes the teeth more sensitive to heat, cold, and touch.

Teeth aren’t the only parts of the body to get battered by bruxism. Gums can give way under the pressure and recede, while the intense gripping can inflame the hinge of the jaw, the temporomandibular joint. People already suffering from other disorders of the jaw or arthritis may find that nighttime tooth grinding only exacerbates the existing conditions.

All this somnolent activity gives the masseter, the muscle largely responsible for closing the jaw, one hearty workout. Over time, the masseter can become so brawny that it will lend a square shape to the outline of the jaw. People suffering from masseter hypertrophy may wake up with a charley horse-type ache; in severe cases they may be unable to open their mouths. And as if that weren’t painful enough, bruxers are more prone to morning tension headaches because the muscles and ligaments of the face are so intimately connected.

So if grinding your teeth in sleep is so destructive, why do people spend their precious downtime champing at a nonexistent bit? “Surprisingly, the reason why some people are grinding their teeth during sleep remains largely unknown,” says physician and sleep researcher Maurice Ohayon of the Stanford University Sleep Disorder Center (CA).

Experts believe that almost everyone bruxes at some point in life, but to varying degrees. “It’s just a normal thing we do in our sleep, much like snoring or dreaming,” says Steven Graff-Radford, a dentist and director of the Pain Center of Cedars Sinai Medical Center in Los Angeles. However, “If you grind so loud that you or your partner can’t sleep, if you’re wearing your teeth away, it needs to be addressed.”

Theories to explain why people grind so hard range from bite fit problems (malocclusion) to stress. To examine the risk factors, Ohayon and colleagues at Regensburg University in Germany asked 13,000 people in Italy, Germany, and the United Kingdom about their sleeping and nocturnal teeth-grinding habits. The results suggest that the biggest risk factor for bruxism is a pre-existing sleep disorder. Sleeping bruxers were much more likely to suffer from breathing problems such as apnea or snoring, to talk in their sleep, and to experience hallucinations while in transition from one sleep stage to another.

Severe life stress was the second most common factor. The connection between tension and tooth wear has already been demonstrated vividly in the laboratory. “If people are shown a movie like Woody Allen’s Sleeper just before they go to bed, their level of bruxism doesn’t change. If, on the other hand, people were shown Apocalypse Now, their level of brux went up dramatically,” Graff-Radford says.

The unconscious clenching and grinding of sleep bruxism are also likely to appear with certain lifestyle habits: Heavy alcohol drinkers, smokers, and those who drink six cups or more of coffee per day are much more likely to grind their teeth.

The best way to treat bruxism depends on its immediate cause. For people whose bruxing may be an unconscious means of coping with tension, taking the time to relax before bed can go a long way toward alleviating symptoms. Soaking in a hot bath, listening to soft music, or meditating have been shown to ease the severity of grinding.

Those who can’t fit relaxation into their schedules have literally been known to talk themselves out of the habit. In one study, adults suffering from bruxism were told to stand before a mirror just before bed and say to their reflection, “I do not need to grind my teeth tonight.” That simple verbal cue decreased their grinding dramatically.

For bruxers who smoke or drink alcohol or coffee, giving up their chemical habits is likely to help. To temporarily ease headache or jaw pain, bruxers can turn to over-the-counter muscle relaxants such as ibuprofen or can apply hot compresses to the masseter muscles.

Occasionally, some bruxers start grinding after recent dental work. These people may be grinding in an unconscious effort to smooth down uneven or unfamiliar edges of crowns and fillings. In these cases, patients should have the offending ridges filed down. By the same token, people with bite problems might want to consult an orthodontist about braces or a retainer.

The most common treatment by far for bruxism is a mouth guard or splint similar to those worn by boxers to protect their teeth. The idea is to disrupt the muscle memory by repositioning the jaw, while protecting tooth surfaces from extra wear. It also keeps the jaw slightly open, which takes pressure off the jaw joint. The opportunity to rest the joint can sometimes help people having difficulty opening their mouths to recuperate.

To make a bruxing splint, a dentist makes a plaster mold of the upper or lower set of teeth and uses the mold to customize a thin, pliable plastic or hard acrylic appliance that fits over the teeth. While both versions are popular among dentists, both Graff-Radford and Richard Price, a Boston dentist and a consumer adviser for the American Dental Association, prefer the more rigid version. “If you put something soft like a mouth guard for sports in your mouth, you’re more apt to clench and grind, because you can rip into it like a chew toy,” Price says. Stronger bruxers have been known to bite right through their splints, so a hard plastic version may also last longer. Customized mouth guards can cost $300–$700, so durability is important.

Small children, who have three times the rate of bruxism as adults, generally can’t wear a splint because it interferes with the eruption of their permanent teeth. Experts say bruxing doesn’t harm most children, and many outgrow the problem along with their baby teeth, possibly because permanent teeth are more sensitive to pain.

Although bruxism may grind to a halt in the first few weeks or months in which a splint is worn, some bruxers seem to acclimate to the device and eventually resume the habit. In those cases, the patient might consider seeking additional treatment for the problem.

More Extreme Measures
Modern medicine has come up with some wildly creative solutions to the few severe cases of bruxism that can’t be managed with a splint. These include electromyograph machines that sense the amount of muscle activity in the jaw. Before bed, the patient places electrodes on the cheek and face. If the electrodes pick up muscle patterns similar to that of grinding, the device will awaken the patient with an alarm. But these machines have their drawbacks. Movements as minor as smiling or turning over can set them off, and some exhausted patients learn to sleep right through the bell, which undoubtedly irritates their bed partners.

A less elaborate device relies on taste aversion to train patients not to grind in their sleep. This retainer-like device holds wax capsules of bitter liquid, such as seawater, in place atop the molars. If the wearer grinds his or her teeth, the capsules rupture, which hopefully stops the activity.

Surprisingly, there’s even a pharmaceutical remedy for grinding. Sleep researchers have shown that people are more likely to brux as they move between sleep stages or during REM sleep. Because they decrease the number of awakening stages of sleep and decrease the amount of REM sleep, tricyclic antidepressants, such as imipramine or amitriptyline, can help patients reduce grinding. However, these drugs can have serious side effects, such as disturbing the normal rhythm of the heart and sexual dysfunction, and should only be used as a last resort.

Botox Injection
Possibly the most bizarre treatment for bruxism is strangely similar to a cosmetic treatment for preventing forehead wrinkles—injecting paralyzing botulinum toxin, or botox, into the muscles of the jaw. In one study, researchers carefully injected small doses of botox into the masseter muscles of 18 patients with intractable bruxism.

The treatments permanently stopped one subject’s grinding, but offered only a temporary fix of five months on average for the rest. But because the treatments are expensive and require a doctor to exercise substantial skill to avoid complications from jaw muscle paralysis, botox treatment isn’t practical for most patients.

Instead, people with intractable cases of bruxism should probably consult a doctor specializing in the treatment of orofacial pain. After a comprehensive assessment of factors such as the position and health of the jaw joint and muscles, bite position, the presence of migraine or tension headaches, and lifestyle habits such as alcohol and caffeine consumption, the specialist can often come up with a practical solution to the problem.

Further Reading

(All sites accessed in August 2001.)

Kathleen Wong is a senior editor of California Wild, the magazine of the California Academy of Sciences, and is based in Pacifica, CA. Send your comments or questions regarding this article to tcaw@acs.org or the Editorial Office 1155 16th St N.W., Washington, DC 20036.

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