Posted on 03 Sep 2011 03:49
By Noshir R. Mehta
Professor and Chairman of General Dentistry and Director of the Craniofacial Pain Center
Tufts Dental School, Boston MA
Bruxism is the act of gnashing and grinding the teeth. Bruxism is common in children and adults of both sexes, affecting about 25-30% of children and roughly one in twenty adults. There is no significant difference between males and females .
Bruxism is divided into two main types- Nighttime grinding and daytime grinding. Nighttime grinding (nocturnal bruxism) is a back and forth, side-to-side motion where the lower teeth rub against the upper teeth, creating a characteristic grinding sound. Daytime grinding (clenching) is a rocking motion of the lower teeth against the upper teeth without the teeth actually making the side-to-side motion. While bruxing only happens during sleep, clenching can occur both during the day and at night . Both nocturnal bruxism and clenching are “parafunctional activities,” as they are not part of normal chewing and swallowing.
Why is bruxism dangerous? Normal chewing has been shown to apply forces of around 25lbs to 50lbs (roughly 11-22 Kgs) on the back molar teeth. Parafunctional clenching or grinding, on the other hand, has been shown to create forces as high as 250 lbs (113.6 Kg) during sleep . During normal chewing, the upper and lower teeth come into contact only for about 25-30 minutes in a 12-hour day. During nocturnal bruxism, however, teeth may be in contact as much as 40 minutes per hour of sleep. The increase in both force and contact between teeth is impressive, and can lead to a variety of dental conditions .
During the day, the individual has the ability to control the parafunctional activities. Once the individual falls asleep, however, this ability is lost. As such, the majority of diagnoses and treatments are aimed at reducing nocturnal bruxism or nighttime tooth grinding. Because most adults will grind in their sleep at some time in their life, sleep bruxism has been considered by some to be a physiological release mechanism for stress. This leads them to view it as a positive symptom, and to discourage treatment . While this may be true of bruxism in the milder form, as the duration and severity of grinding increases there is more concern about such forces causing damage to the masticatory system of teeth, bones, muscles, and nerves.
Signs and Symptoms of Nighttime Bruxism
- Rhythmic crunching or grating noises resembling chewing on crackers or on ice
- Headaches and stiffness of the neck upon awakening in the morning
- Muscle pain in the jaw muscles or a feeling of tightness in the jaws
- Awakening with the teeth clenched together
- Temporomandibular joint pain and clicking sounds
- Chronic facial pain
- Ear pain, stuffiness, or even ringing of the ears
- Increased tooth sensitivity, especially in the morning, which slowly gets better as the day progresses
- Wearing of the teeth, chipping or fractures to the teeth in the absence of trauma
- Chewing of the inner aspects of the cheeks or biting of the tongue
- Teeth that are loose or moving
- Inability to chew without jaw muscles tightening and feeling tired
- Tiredness and sleepiness in the daytime 
Damage from Nighttime Bruxism
The damage from daytime clenching and nighttime bruxism primarily affects the dental structures. Here a concept of the “Weak Link theory” comes into effect. The Weak Link Theory relies on the principle that bruxism causes damage to the teeth, the gums, and their supporting bones -the jaw joints (TMJ) and supporting muscles- but very rarely all three . Whichever area is the weakest will be the first to be affected by bruxism, and what is affected can vary from patient to patient. This often leads to misdiagnoses, as some dentists have been trained to look for only one symptom of bruxism.
Dental damage is usually noticed by the dentist as wear of the tooth structures (enamel and dentin) occurring between your regularly scheduled dental visits. You may also notice the wear on the lower front teeth yourself when you look in the mirror to brush or floss your teeth. To check if this wear is from bruxism, try to match the edges of the upper teeth to the worn shapes of the lowers by moving your jaw around. If there are matching worn surfaces, this suggests the position of your grinding pattern at night .
Dentists look at worn or flattened teeth as a sign of active bruxism (see image above for an example of worn teeth). However, the wear could have been created at an early age and then, like the Grand Canyon formed by the effect of water over time, the patterns remain. Teeth once worn will always show the wear unless new fillings or crowns are created to cover the worn surfaces. The only sure ways to tell if active grinding is still going on is if you wake yourself up by grinding or if a family member hears the sounds while you sleep. There are some dental guards, such as a Bruxcore diagnostic guard or some surface Electromyography (EMG) techniques, that indicate bruxism . By and large, however, it is the self-report that is the best evidence of bruxism .
Depending on the severity of the bruxing, you may also have fracture lines or tiny chips breaking from the grinding surfaces of the teeth. Excessive force can sometimes lead to the need for a root canal if the wear reaches the inner surfaces of the teeth, causing an inflammation of the nerve (pulp) of the tooth. Forces on the teeth can sometimes cause a bending of the tooth at the gum margin. If the bending is to the outer gum side, there is a shearing of the outer layer of tooth structure called an abfraction. An abfraction is a shiny, smooth, scooped out gouge on the outer surface of a tooth, usually in the back teeth, caused by rocking forces on the tooth.
Periodontal and Bone damage
In the presence of existing gum inflammation (gingivitis) or infection (periodontal disease), bony changes can occur from excessive force on teeth over an extended period of time. This has been termed “trauma from occlusion,” and is a potential consequence of bruxism. This can lead further to bone loss, loosening of the teeth, mobility of the teeth, or even tooth movement related to the reduction of the bone support for the tooth .
Temporomandibular (TMJD) and muscle damage
If the teeth do not wear and the surrounding bone is strong, the forces of bruxism can cause damage to the muscles and the joints of the jaw.
Clicking, popping, and grating sounds are indicators of internal damage to the TM Joints and can possibly lead to dental instability and difficulty chewing. Pain in the muscles of jaw and tension of the neck muscles leading to headaches and neck pain are also common consequences of nighttime bruxism. Chronic clenching and grinding have also been known to trigger nerve-related pain and sometimes appear as sharp shooting pains mimicking Trigeminal Neuralgia, or tooth pain such as Atypical Odontalgia .
Conditions related to Bruxism
Bruxism is also considered to be a sleep-related disorder in the same family as sleepwalking and restless body movements. It occurs during stage 2 sleep, the Rapid Eye Movement (REM) stage of sleep, and during the change from deeper to shallower levels of sleep. Bruxism therefore can also affect the nature of sleep while being affected by it. Bruxism also has an impact on mood and brain wave activity, and can raise anxiety and pulse rate .
Common causes of Bruxism
There is no clear consensus on what causes people to clench or grind their teeth at night. However, the following causes are generally agreed upon:
In children, bruxism is most common around 5 to 7 years of age, during the time of growth and development of the jaws. This is also considered to be the start of the mixed dentition period- when children begin to develop their new teeth. The working theory is that discomfort from irritation to the gums caused by new teeth coming into the mouth, along with an unstable bite, triggers the need for clenching and tooth grinding in children.
Pain from other issues, such as earaches, tonsils, and adenoids, may also cause grinding in children. Sometimes food allergies, such as to milk or dairy products, can lead to grinding. As with adults, anger, frustration and tension, as well as certain medications for childhood behavior such as ADHD, can also increase grinding.
In most children, bite appliance therapy is quite effective. The good news is that bruxism in children almost always goes away as the child grows older and no ongoing treatment is necessary .
In adults, there are four main causes of bruxism– dental, psychological, neurological, and sleep related.
Bruxism from Dental Causes
Misalignment of teeth and unstable tooth contacts can act as triggers for tooth grinding. Dentists will point out that high fillings or poorly fitted crowns on teeth often show wear, as if nature was intending to grind away the offending contact. On the other hand, dental interferences are a part of most bites and research has not shown them to be a factor in bruxism. It is more likely that if there is a dental cause in the individual, it has to do with the upper teeth interfering in a comfortable path of closure of the lower jaw, causing a restriction or a feeling of entrapment of the lower teeth. Tooth grinding in this case leads to wear of the teeth in the specific area of such an entrapment .
Bruxism from Stress and Psychological Causes
It has long been noticed that people tend to grind more under periods of increased stress. This has led to the psychological model of bruxism. It has been found that A-type personalities who are competitive and aggressive in daily life, or those who have issues with anger, frustration, and chronic stress, often grind their teeth more frequently than their more relaxed counterparts.
Although bruxism has been related to stress, there are questions as to which comes first, as the evidence has not been conclusive. However, we do know that stress acts as a predictor of increased bruxism, as stress and certain personality traits tend to be higher in individuals who grind their teeth at night .
Bruxism from Neurological and Medicinal Causes
Central nervous system related nerve transmissions can be affected by medications and can lead to bruxism. Selective serotonin reuptake inhibitors (SSRIs) prescribed for depression have been known to be associated with several movement disorders such as tardive dyskinesia and parkinsonism. Patients taking fluoxetine or sertraline for depression often develop bruxism within the first few weeks of taking the new medications. In addition, children and adults who are on medication for Attention Deficit Hyperactivity Disorder (ADHD) also report a higher incidence of tooth grinding.
Certain herbal remedies cause an increase in nervousness and heighten the anxiety response, which can lead to nighttime grinding. Food allergies, such as with milk and dairy products, have also been suggested as additional causes of tooth grinding. Alcohol consumption has also been shown to increase bruxism. In fact, the greater the consumption of alcohol, the higher the incidence of bruxism. For this reason, a full list of herbal medications, vitamins, minerals, food allergies, and any medications you are on should be disclosed to your dentist or physician if you are concerned that you have bruxism .
Bruxism from Sleep Related Causes
Nighttime bruxism is the third most common sleep disorder in the general population. Individuals with chronic snoring, obstructive sleep apnea, and other sleep-related disorders are also predisposed to bruxism. Polysomnography or overnight sleep studies are the standard for evaluation of sleep-disordered bruxism .
How can I find out if I have Bruxism?
Doing some of the following tests at home can help you decide whether you should see your dentist or physician.
- As mentioned before, you can look at your teeth in the mirror and see if you have any worn lower or upper teeth. The most common form of nighttime bruxism tends to cause wear to the upper and lower eye (canine) teeth.
- You can ask a member of the family to look into your mouth to see if any teeth are worn or shiny on the inside and outside parts of the chewing surfaces.
- You can run your tongue over the upper and lower teeth to check for sharp edges and rough spots on the teeth, suggesting that the teeth have been rubbing against each other.
- Wash your hands thoroughly and then run your fingers over the teeth to check for rough areas that your tongue might have missed.
- If you have jaw pain or have a habit of clenching in the daytime.
- If you wake up with headaches on the sides, the front, and/or back of the head on a regular basis.
- If you have daily chronic neck stiffness and/or pain in the neck upon awakening.
- If you have difficulty chewing food.
- If you get tooth pain that comes and goes.
- If you have bleeding gums or loose teeth that you can wiggle with your fingers or tongue.
- If you hear noises in your jaw joints or experience pain in the jaw joints on opening and closing of the mouth.
- If you have anxiety and/or constantly feel depressed, you may be at greater risk for bruxism.
- The dentist will first ask for a full history of your problem. It is best to take some time before your visit to make a list of your symptoms. You will need to list all the medications you are taking and have taken in the last few years, including any herbal remedies or vitamin and mineral combinations you are taking. These are important as the dentist or physician will need to know about potential interactions that could be causing nervousness and hyperactivity.
- The dentist will conduct an intra-oral dental examination of the teeth for cavities, wear of the teeth, missing teeth, and signs of injury to the gum tissues.
- An intra-oral examination of the tissues of the cheek, tongue and the roof of the mouth will be done as part of a cancer check.
- An examination of the head and neck muscles and the temporomandibular joints will be done to evaluate the effects of bruxism. The dentist may ask to check your range of motion of the head and neck as well as the jaw to assess the tension level in the muscles.
- If you snore or wake yourself up gasping for breath, you may need to speak to your physician or a dentist who is familiar with sleep apnea. This is important if you also have signs of daytime sleepiness and fatigue since these can have serious consequences if you drive or handle machinery.
- If you are diagnosed with bruxism you should also check with your physician to see if your condition can affect your general health.
- If you have ear symptoms of pain, ringing, dizziness, or stuffiness of the ears your physician may want you to see an ENT (ear nose and throat) doctor.
- If you are experiencing heightened stress, anxiety, or are feeling blue you should talk to your dentist or physician to see if a referral to a psychologist or psychiatrist would be appropriate.
- If you are having headaches, you should see your physician, who in turn might refer you to a headache specialist or a pain center.
What can I do for my Bruxism?
- Do not eat or drink at for least one hour before bedtime.
- Do not drink alcohol at night. A glass of wine may calm you but alcohol in any quantity has been found to aggravate bruxism.
- Do not take vitamins, minerals, or any herbal medication that might excite you at night before bed.
- Do not work up to the time you plan to go to sleep. Let yourself relax and settle down before you plan on going to bed.
- Use techniques of deep breathing and progressive relaxation before bedtime.
- If you have pain in the face or jaw, use ice on your jaw joints or a wet hot towel on the face to help relax the muscles until you can get to the dentist.
- Analgesics like Tylenol, Aspirin, Advil, or Aleve can help reduce minor pains. If the pain continues for more than three days you should see your physician or your dentist.
- Stretching the jaw muscles can help relax them. Take the knuckles of your hands, place them under your cheek-bones and slowly drag them down towards the angles of your jaws on both sides while keeping your teeth apart and repeat the stretch five times. You can repeat this five to six times a day if needed.
- Another stretch you can try involves your tongue. Placing your tongue tip behind the upper front teeth, slowly open your mouth to a slow long stretch. Only open until you feel a stretch and not if you have pain when you do so.
- There are over-the-counter mouth guards that have been now approved by the U.S. Food and Drug Administration for bruxism or tooth grinding. These are usually “boil and bite guards” that can be used on a temporary basis till you see your dentist. They are usually found at your local pharmacy or larger stores that carry healthcare products.
Mild bruxism does not generally need treatment unless your dentist sees the beginnings of wear on your teeth. Moderate or severe bruxism requires treatment.
The primary treatment by a dentist is a night guard. The dentist will take impressions of your teeth and then make a formed, hard upper night guard that covers your teeth and prevents the upper teeth from coming together with the lower teeth. Some dentists will make a lower guard, depending on your bite and the structure of the teeth. If there is a misalignment of the teeth that the dentist thinks is triggering your grinding, he or she may plan dental treatment such as caps or crowns or orthodontics to help the bite fit better.
Sometimes your dentist may prescribe a night guard covering all of the upper or lower teeth, or a guard covering only the front upper teeth, for clenching and headaches. If the teeth have previously been damaged, the dentist will fix your teeth first and then prescribe a night guard to prevent damage of the new bite. If you grind and have daytime jaw pain, headaches, and neck pain, the dentist may also add a day guard to get the muscles and joints to relax and rest .
You will be given relaxation training techniques by your dentist or physician. Techniques include biofeedback, which teaches you methods of relaxation in front of a computer that allows the therapist to show you how to relax. Psychological counseling or psychiatric treatments can also help reduce the tension in your body and jaw muscles while helping to keep the teeth apart at night when you sleep .
You may be placed on muscle relaxants or anti-anxiety medications to help you relax if you have trouble falling asleep, or antidepressants if you have trouble staying asleep. It is very important to be honest with your doctors about your stress levels, whether at home or at work, as chronic stress can ultimately be bad for your overall health.
Your dentist or sleep physician may have you participate in a sleep study. Usually this is done in a hospital sleep laboratory and you will need to sleep overnight in the lab. Lately there has been a push to have out-of-the-hospital sleep systems since it is difficult for some patients to sleep overnight in a strange environment. Even though the traditional hospital sleep study is the gold standard, newer at home sleep systems such as the Watch-Path 100 can be initially useful in demonstrating sleep bruxism and sleep apnea. Follow up assessments should be done by dentists or physicians who are trained in dental sleep medicine and who work closely with sleep physicians and sleep laboratories .
Dental guards for sleep apnea should be tried only after you have had a failed treatment with a Continuous Positive Airway Pressure (CPAP) machine, which is used as a respiratory ventilator. Dental sleep guards can help for bruxism as well as for mild to moderate sleep apnea .
Some medications, including older antidepressants such as Amitriptyline or nortriptyline, have been used in bruxism. Other muscle relaxants such as Cyclobenzaprine have also been used to help change the nature of sleep to reduce bruxism .
Mild bruxism does not require treatment. Moderate bruxism may need a dental night guard to protect the teeth if no other symptoms are in evidence. This may be particularly indicated if you have had orthodontics, implants, gum surgery or crown and bridge work. In severe bruxism, a multidisciplinary approach of a night guard along with medication and psychological counseling is necessary. Reducing your overall stress will help make any treatment more effective. If sleep apnea is an additional factor, then a sleep guard may be added only after a trial of the CPAP machine has been tried.
Noshir R. Mehta. Bruxism:Tooth Grinding and Clenching [Internet]. Version 16. Knol. 2008 Jul 23. Available from: http://knol.google.com/k/noshir-r-mehta/bruxism/D3iAfFNV/kRAr4Q.