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 subjects 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.
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 20s and 30s 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.
Figure2-various layers of tooth structure causing severe sensitivity
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.
- 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.
- 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.
- 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
- 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.
- 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.
Figure 4: Front to back fracture of the lower molar
- Waking up in the middle of the night and finding yourself clenching your teeth together
is not uncommon.
- You may have morning headaches in the temporal areas.
- You may suffer from stiff neck and shoulders.
- 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
- 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
Figure 5: Sensitive areas on the neck of teeth
are usually indicative of severe clenching
- 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.
Figure 6: Jagged and chipped front teeth resulting from grinding.
- 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.
Figure 7: Due to their very slow formation, patients are
never aware of the presence of such growths.
- 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.
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.
- The first thing is to go to your dentist and let him confirm the diagnosis.
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.
- 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.
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.
- 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.
- Psychological counseling can help when stressful stimuli cannot be self-controlled.
- 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.
- 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.
- 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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