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Preventative Dentistry
Grinding and Clenching

You brush and floss your teeth, you go to the dentist 3-4 times a year, you do what the dentist recommends and you get a clean bill of health each time. If you keep this up, you would expect to hang on to your teeth as long as you live. Right? For only 20% of us this may hold true, but the rest of us would “wear” our teeth to distinction long before we die.

The current state of the mouth

Most of the population born in the past 40 years and brought up in the metropolitan areas of the developed world have benefited from various sources of fluorides and are well educated in good oral hygiene habits. In fact, data from Pan American Health Organization country members, indicate that most of the countries have reached the World Health Organization year 2000 goal of a mean Decayed Missing Filled-Teeth of 3 or less. We see a good segment of this group having healthy teeth, with few if any well controlled and stopped cavities. Majority of them have very healthy gums, which is keeping their intact healthy teeth tightly in place. The tooth enamel would last a lifetime if it were used only for the purpose that it is created. During mastication, for most of the time, we have the food bolus between the teeth, protecting the opposing enamel surfaces from each other. Therefore chewing food is hardly abrasive to the enamel. The only substance that is present in mouth and is hard enough to wear and destroy the tooth enamel is the enamel from the opposing jaw. The life expectancy of humans has increased by decades in the past century. The longevity of these otherwise healthy teeth has become a great concern to the health conscious. During normal function, opposing teeth surfaces contact each other directly for a total of less than 10 minutes every 24 hours. The average pressure during normal function is 58.7lb. This represents 36.2% of the subject’s maximum bite force (1). These forces are well tolerated for 90 to 100 years of service.

The danger at hand

The trouble starts when we contact the opposing teeth without any food in between them, for long periods of time and higher pressures. Squeezing the teeth together is called clenching. Grinding the teeth together is called bruxing. Since none of these acts are part of the normal function of the stomatognathic system, they are called “Para function”. Based on the examination of over 4500 patients in the metropolitan Los Angeles during the past 14 years, I have discovered that an increasing number of individuals (about 6 out of 10) are in the danger of losing most or all of their teeth prematurely as the result of these “excessive forces”. In other words, the people who have healthy individual teeth have the potential of destroying their teeth through Para function by causing severe attrition, fracture and /or necrosis of the teeth.


Causes of Tooth Loss Chart

Figure 1 - Causes of Tooth Loss


Para function takes place usually during sleep, totally unknown to the conscious mind. It is much like snoring that takes place during sleep and stops upon awakening. The enamel that was meant to be in contact with the opposing enamel for only a few minutes during a 24-hour period is ground against the opposing enamel for 38.7 minutes (2) during an 8-hour sleep period. The force of nocturnal bruxing is from 66% of maximum biting force to more than the maximum (3). In more severe cases, it continues during the waking hours or while engaging in certain activities such as lifting weights. On average, the duration of tooth contact is increased 8 folds while the force of this contact is at least doubled. In other words, the teeth are subjected to at least 16 times more wear in a person engaging in Para function. I have seen many individuals in their 20’s and 30’s who have totally worn out their enamel and have exposed the dentine (the second and much softer layer under the enamel). Much like the periodontal disease, Para function is initially painless and progresses gradually and therefore is overlooked until the condition is quite advanced. The fact that all the teeth in the mouth are affected simultaneously and more or less to the same degree by this condition further complicates the consequences of Para function.


Tooth Structure
Figure2-various layers of tooth structure causing severe sensitivity


Exposed dentinal layer
Figure3-Exposed dentinal layer


Causes of Para function in adults:

There have been many reasons given for grinding and clenching of the teeth. It would be safe to assume that in most cases, combination of two or more of these factors are responsible for the destruction of teeth. The scientific community has not yet discovered all of the factors involved.

  1. Structural triggers: Bite discrepancy is the basis that triggers grinding and clenching. There are two distinct mechanisms at work. Type I discrepancy is the discrepancy between the most comfortable position of the jaw joint and the most comfortable way that the teeth come together. Most people do have this bite discrepancy but not all of them grind or clench their teeth. This is the more common bite problem but in absence of the second type of bite discrepancy, it usually does not cause much damage. Type II discrepancy results in absence of physiological guarding and feedback mechanisms that are naturally present in the front teeth. For the front teeth to provide this protection, the lower front teeth must be aligned in a certain close arrangement with the upper front teeth. When this “guarding” is not present, the back teeth can run into each other antagonistically in function and Para function, destroying each other.

  2. Psychological triggers: What makes this bite discrepancy become seriously detrimental is usually nervous tension. Stress makes the muscle fibers more responsive to the stimulation from brain. Therefore the discrepancy, which is usually accepted by the body and does not elicit any significant response, brings out a strong reaction in presence of stress. People that engage in Para function, may notice that when they are under stress they do it with much more frequency and severity.

  3. Chemical triggers: Intake of “uppers” such as caffeine and amphetamines synergistically enhance the contractions of the jaw muscles. Hence the use of these drugs can bring about rigorous clenching and grinding. Withdrawal from drug dependencies like nicotine and cocaine is also to be blamed for very harsh and callous clenching and grinding. It is not unusual to see these patients split an otherwise normal and healthy tooth (typically the lower first molar) in halves requiring immediate removal of the tooth to relieve the severe pain. Certain prescription drugs like the anti-depressant, Zoloft is known to induce Para function.

  4. Habituation: It is important to realize that after years or even months of grinding and clenching, the act itself becomes a “habit”. Therefore, even if one reduces or eliminates all the above factors, one cannot expect to completely stop this behavior, without addressing the habit itself.

Diagnosis of Para function

Much like diagnosis of many other diseases, there are no “litmus tests” for this condition. Your dentist must make the final determination after considering all the factors and thorough examination of your bite and jaws. The following are some of the evidences that suggest presence of Para functional activity.

In an acute case, you may be going through an unusually stressful period of your life. It could be as trivial as preparing to leave for a vacation or moving to a different place or it can be more traumatic as in the loss of a loved one or a divorce.

  1. In the very acute form, most people are totally unaware of their nocturnal behavior and are given the news by their dentist when they go for an emergency toothache appointment! The dentist tells you that a tooth is cracked or fractured. The tooth mainly involved is the most heavily restored tooth in the mouth, the lower first molar.


Tooth Loss
Figure 4: Front to back fracture of the lower molar


  1. Waking up in the middle of the night and finding yourself clenching your teeth together is not uncommon.

  2. You may have morning headaches in the temporal areas.

  3. You may suffer from stiff neck and shoulders.

  4. You may find the teeth to be sore, especially upon awakening. You complain that “all” your teeth hurt.

If clenching becomes chronic and goes on for a long enough period of time:

  1. There may be cold and touch sensitivity associated with the neck of the teeth. Typically, the patient feels an “electric shock” sensation when she scratches the outside surface of the neck of the upper teeth with her nail. These areas are usually covered by gum but with chronic clenching, a condition called “abfraction” takes place. Abfraction is a condition in which the neck of the tooth is eroded away in a chemical reaction as it flexes under clenching and grinding forces. As a result of this, the dentinal surface becomes exposed and that area becomes extremely sensitive. The presence of the wedge shaped erosions in a sensitive form is usually the evidence of clenching and grinding. If the person stops the clenching and grinding the wedge shaped spaces will remain but the sensitivity will stop.


Grinding Teeth
Figure 5: Sensitive areas on the neck of teeth
are usually indicative of severe clenching

Grinding Teeth


  1. Excessive wear facets that are flat and shiny on the top of the back teeth, inconsistent with the age of the individual, is a sign of grinding. Thinning and chipping of the front teeth is another sign of excessive wear from grinding.


Excessive Tooth Wear
Figure 6: Jagged and chipped front teeth resulting from grinding.


  1. Formation of extra bone around the teeth, most commonly on the inside surfaces of the lower premolars. Previously these bone formations that are called “tori” were thought to be of genetic origin.


Extra Bone Formation
Figure 7: Due to their very slow formation, patients are
never aware of the presence of such growths.


  1. Clenching is usually associated with the outward pressing on the teeth by the tongue. This will leave the impression of the teeth as indentations on the sides of the tongue and it is called “scalloped tongue”. This is usually associated with a white line on the inside of the cheeks running parallel to the biting surfaces of the teeth.


Scalloped Tongue
Figure 8: Scalloped tongue is a sign of continuous clenching
accompanied by pressing on the teeth by the tongue.



Occasional periods of increased jaw muscle activity and Para function which is directly associated with short-lived stress does not have any long-term consequences.

If you suspect that you may be damaging your teeth, there are a number of steps that you can take to preserve your teeth.

  1. The first thing is to go to your dentist and let him confirm the diagnosis.

  2. Dental SplintPerhaps the most immediate, least expensive and most effective way of stopping the damage and severity of grinding and clenching is through the making of a repositioning splint. A repositioning splint looks like the traditional night guard but has certain functions built into it. This device not only protects your teeth when you do grind but in addition, it reduces your urge to grind. It does that by totally eliminating the Type I discrepancy and incorporating the natural and physiological guarding and feedback mechanisms.

  3. If there is a bite discrepancy, the dentist can guide you in correcting that discrepancy. It is not always easy to correct the Type II discrepancies. Neither is it necessary to correct every bite discrepancy. The treatment can range from selective grinding on some of the teeth to orthodontic treatment to jaw surgery,
    depending on the extent by which the front teeth are separated.

    In most cases where the separation is enhanced by the “wearing down of the tooth”, the lost enamel can be replaced and the front teeth properly aligned by restorative materials. If the separation is within range, this method is highly effective, relatively easy and free from any adverse effects.

  4. In some cases, the costs, risks and time involved for these procedures do not warrant attempting them. Correcting bite discrepancies takes very special skills, training and instrumentation. In spite of numerous studies, in absence of this preparation, some clinicians have gone as far as asserting that bite discrepancies are not related to Para function and jaw joint problems. They recommend supportive measures that will mostly help the patient in short term but has questionable long-term prognosis. Much like leaving the offending nail in a flat tire and patching over it.

  5. In a very acute stage and for a very short period of time like a few days, muscle relaxants prescribed by a dentist or physician can help.

  6. Psychological counseling can help when stressful stimuli cannot be self-controlled.

  7. Moist heat applications. Available from drug stores, these gels can be heated in microwave oven and placed directly on the side of the face from bottom of the jaw to top of the head. Heat relaxes the muscles and therefore reduces their detrimental effects.

  8. Avoid “training” of the jaw muscles-avoid chewing gum. Chewing gum directly reduces the life of your teeth by wearing them many times faster than when you use your teeth to chew your food with. In addition and even worse, it trains your jaw muscles and when you engage in Para function, you damage your teeth many times faster.

  9. Neck exercises and neck and upper back massages. Para function fatigues the jaw muscles and puts them in spasm. Jaw muscles work anta-agonistically with muscles of back of the neck to balance the head. Relaxing and comforting of one of these muscle groups, helps relax the other.


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Parsa T. Zadeh, DDS, FAGD, FICOI
Beverly Hills Center for Reconstructive and Cosmetic Dentistry
9100 Wilshire Boulevard • Suite W448 • Beverly Hills, California 90212

Disclaimer: Dr. Zadeh has performed all the dental procedures shown. The text of this site is written by and is the
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