Teeth Grinding
Bruxism
refers to excessive grinding of teeth and/or excessive clenching of the jaw.
Bruxism is an oral parafunctional activity, that is to say, it is not activity
related to normal function such as eating or talking. Bruxism is a common
problem, with some sources stating that 85-90% of the general population grind
their teeth to a degree at some point during their life, although only 5% will
develop a clinical condition. Bruxism may cause minimal symptoms, and therefore
people may not be aware of the condition. Several symptoms are commonly
associated, including hypersensitive teeth, aching jaw muscles and headaches.
Bruxism may also cause tooth wear, or even cause teeth to break and dental
restorations (e.g. crowns and fillings) to be repeatedly lost or
damaged.
There
are two main types of bruxism, namely bruxism which occurs during sleep (sleep
bruxism) and bruxism which occurs during wakefulness (awake bruxism). The damage
to the teeth is similar in both types, but the symptoms of sleep bruxism are
usually worst upon waking and then slowly get better over the day, and the
symptoms of awake bruxism may not be present at all upon waking, and then slowly
get worse over the day. The causes of bruxism are not totally understood, but
probably involves multiple factors. Awake bruxism is thought to have different
causes to sleep bruxism, and is more common in females whereas males and females
are affected in equal proportions by sleep bruxism. There are several treatments
in use, although there is very little evidence for any particular treatment in
the management of bruxism
Bruxism is
derived from the Greek word βρυγμός (brygmós), meaning "gnashing of teeth".
People who suffer with bruxism may also be called "bruxists", and the act itself
"to brux". There is no widely accepted definition of bruxism, but some suggested
definitions include:
"A
movement disorder of the masticatory system charactized by teeth grinding and
clenching during sleep as well as wakefulness."
"Non-functional contact of the mandibular and maxillary teeth
resulting in clenching or tooth grinding due to repetitive, unconscious
contraction of the masseter and temporalis muscles."
"Parafunctional grinding of teeth or an oral habit consisting
of involuntary rhythmic or spasmodic non functional gnashing, grinding or
clenching of teeth in other than chewing movements of the mandible which may
lead to occlusal trauma."
"Periodic repetitive clenching or rhythmic forceful grinding of
the teeth."
Classification by temporal pattern
Bruxism can
be subdivided into two types based upon when the parafunctional activity occurs
- during sleep ("sleep bruxism"), or whilst awake ("awake bruxism"). This
distinction is most widely referred to since sleep bruxism generally has
different causes to awake bruxism, although the affects of condition on the
teeth are the same. The treatment is also often dependent upon whether the
bruxism happens during sleep or whilst awake. E.g., an occlusal splint worn
during sleep in a person who only bruxes when they are awake will probably have
no benefit. Awake bruxism is sometimes abbreviated to AB, and is also termed
"diurnal bruxism", DB, or "daytime bruxing". Sleep bruxism is sometimes
abbreviated to SB, and is also termed "sleep-related bruxism", "nocturnal
bruxism", or "nocturnal tooth grinding"). According to the International
Classification of Sleep Disorders revised edition (ICSD-R), the term "sleep
bruxism" is the most appropriate since this type occurs during sleep
specifically rather than being associated with a particular time of day, i.e. if
a person with sleep bruxism were to sleep during the day and stay awake at night
then the condition would not occur during the night but during the day. The
ICDS-R defined sleep bruxism as "a stereotyped movement disorder characterized
by grinding or clenching of the teeth during sleep", classifiying it as a
parasomnia. The second edition (ICSD-2) however reclassified bruxism to a "sleep
related movement disorder" rather than a parasomnia.
Classification by cause
Alternatively, bruxism can be divided into primary bruxism
(also termed "idiopathic bruxism"), where the disorder is not related to any
other medical condition, or secondary bruxism where the disorder is associated
with other medical conditions. Secondary bruxism includes iatrogenic causes,
such as the side effect of prescribed medications. Another source divides the
causes of bruxism into 3 groups, namely central or pathophysiological factors,
psychosocial factors and peripheral factors. The World Health Organization's
International Classification of Diseases 10th revision does not have an entry
called bruxism, instead listing "tooth grinding" under somatoform disorders. To
describe bruxism as a purely somatoform disorder does not reflect the
mainstream, modern view of this condition
Classification by severity
The ICSD-R
described three different severities of sleep bruxism, defining mild as
occurring less than nightly, with no damage to teeth or psychosocial impairment;
moderate as occurring nightly, with mild impairment of psychosocial functioning;
and severe as occuring nightly, and with damage to the teeth, tempormandibular
disorders and other physical injuries, and severe psychosocial
impairment.
Classification by duration
The ICSD-R
also described three different types of sleep bruxism according to the duration
the condition is present, namely acute, which lasts for less than 1 week;
subacute, which lasts for more than a week and less than a month; and chronic
which lasts for over a month.
Signs and
symptoms
Most people
who brux are unaware of the problem, either because there are no symptoms, or
because the symptoms are not understood to be associated with a clenching and
grinding problem. Some individuals clench without significant lateral
movements.
The symptoms
of sleep bruxism are usually most intense immediately after waking, and then
slowly get better, and the symptoms of a bruxing habit which occurs mainly while
awake tend to slowly get worse throughout the day, and may not be present upon
waking.
Long
term effects of severe bruxism on an anterior tooth, revealing the dentin and
pulp which are normally hidden by enamel
Bruxism may cause a variety of
signs and symptoms, including:
Excessive tooth wear, particularly attrition,
but also possibly abfraction.
Tooth fractures, and repeated failure of
dental restorations (fillings, crowns, etc.),
Hypersensitive teeth, (e.g.
sensitivity when drinking a cold liquid)
Inflammation of the periodontal
ligament of teeth, which may make them sore to bite on, and possibly also a
degree of loosening of the teeth,[8]
A grinding noise during sleep (in sleep
bruxism), sometimes detected by a partner or a parent. This noise can be
surprisingly loud and unpleasant, and can wake a sleeping partner.
Cheek
biting (which may manifest as morsicatio buccarum and/or linea alba), and/or lip
biting, (other parafunctional habits which may occur together with
bruxism)
A burning sensation on the tongue (see: glossodynia), possibly
related to a coexistent "tongue thrusting" parafunctional
habit.
Indentations of the teeth in the tongue ("crenated tongue" or
"scalloped tongue"),
Hypertrophy of the muscles of mastication (increase in
the size of the muscles that move the jaw), particularly the masseter
muscle
Tenderness, pain or fatigue of the muscles of mastication, which may
get worse during chewing or other jaw movement,
Trismus (restricted mouth
opening),
Pain or tenderness of the temporomandibular joints, which may
manifest as preauricular pain, or pain referred to the ear
(otalgia).
Headaches, or other facial pain including atypical facial
pain,
Causes
The cause of
bruxism is largely unknown, but it is generally accepted to have multiple
possible causes. Bruxism is a parafunctional activity, but it is debated whether
this represents a subconscious habit or is entirely involuntary. Awake bruxism
is thought to be usually semivoluntary, and often associated with stress caused
by family responsibilities or work pressures. There is evidence that sleep
bruxism is caused by mechanisms related to the central nervous system, involving
sleep arousal and neurotransmitter abnormalities. Underlying these factors may
be psychosocial factors including daytime stress which is disrupting peaceful
sleep. Awake bruxism usually involves clenching, (sometimes the term "awake
clenching" is used instead of awake bruxism), but also possibly grinding, and is
often associated with other semivoluntary oral habits such as cheek biting, nail
biting, chewing on a pen or pencil absent mindedly, or tongue trusting (where
the tongue is pushed against the front teeth forcefully). Sleep bruxism is
mainly characterized by "rhythmic masticatory muscle activity" (RMMA) at a
frequency of about once per second, and also with occasional tooth grinding. It
has been shown that the majority of sleep bruxism episodes occur during periods
of sleep arousal.
Reflex
activities happen reliably in response to a stimulus, without involvement of
subconscious brain activity. Chewing and clenching are complex neuromuscular
activities that can be controlled either by subconscious processes or by
conscious processes within the brain. During sleep, (and for some during waking
hours while conscious attention is distracted) subconscious processes can run
unchecked, allowing bruxism to occur.[citation needed] Some bruxism activity is
rhythmic with bite force pulses of tenths of a second (like chewing), and some
have longer bite force pulses of 1 to 30 seconds
(clenching).
Bruxism can
also be regarded as a disorder of repetitive, unconscious contraction of a
complex set of myofacial muscles; this typically involves the masseter and
anterior temporalis (the large outer muscles that clench), and the lateral
pterygoids, relatively small bilateral muscles that act together to perform
sideways grinding.
The jaw
clenching that is often part of bruxism can be an unconscious neuromuscular
daytime activity, which should be treated as well, usually through physical
therapy (recognition and stress response reduction)
Psychosocial
factors
Many studies
have reported significant psychosocial risk factors for bruxism, particularly a
stressful lifestyle, and this evidence is growing, but still not conclusive. It
has been reported that persons with bruxism respond differently to depression,
hostility and stress compared to people without bruxism. Stress has a stronger
relationship to awake bruxism, but the role of stress in sleep bruxism is less
clear, with some stating that there is no evidence for a relationship with sleep
bruxism.[16] However, children with sleep bruxism have been shown to have
greater levels of anxiety than other children. People aged 50 with bruxism are
more likely to be single and have a high level of education. Work related stress
and irregular work shifts may also be involved.[18] Animal studies have also
suggested a link between bruxism and psychosocial factors. Rosales et al.
electrocuted lab rats, and then observed high levels of bruxism-like muscular
activity in rats that were allowed to watch this treatment compared to rats that
did not see it. They proposed that the rats who witnessed the electrocution of
other rats were under emotional stress which may have caused the bruxism like
behaviour.
Genetic
Some
research suggests that there may be a degree of inherited susceptibility to
develop sleep bruxism. 21-50% of people with sleep bruxism have a direct family
member who had sleep bruxism during childhood, suggesting that there are genetic
factors involved,[19] although no genetic markers have yet been identified.
Offspring of people who have sleep bruxism are more likely to also have sleep
bruxism than children of people who do not have bruxism, or people with awake
bruxism rather than sleep bruxism.
Medications
Certain
drugs, including both prescribed and recreational drugs are thought to cause
bruxism to develop, however others argue that there is insufficient evidence to
draw conclusion between the effect of any medication and bruxism. Examples
include dopamine agonists, dopamine antagonists, tricyclic antidepressants,
selective serotonin reuptake inhibitors, alcohol, cocaine, amphetamines
(including those taken for medical reasons). In some reported cases when bruxism
is thought to have been initiated by selective serotonin reuptake inhibitors,
decreasing the dose resolved the side effect.
Specific
examples include levodopa (used in Parkinson's disease),
methylenedioxymethamphetamine (MDMA, ecstasy), methylenedioxyamphetamine (MDA),
methylphenidate, and gamma-hydroxybutyric acid (GHB) and similar
gamma-aminobutyric acid-inducing analogues such as phenibut. Bruxism can also be
exacerbated by excessive consumption of caffeine such as coffee, tea or
chocolate. Nicotine stimulates release of dopamine, which is postulated to
explain why bruxism is twice as common in smokers compared to non
smokers.
Occlusal
interference
Occlusion is
defined most simply as "contacts between teeth", and refers to the meeting of
teeth during biting and grinding. The term does not imply any disease.
Malocclusion is a medical term referring to less than ideal positioning of the
upper teeth relative to the lower teeth, which can occur both when the upper jaw
is ideally proportioned to the lower jaw, or where there is a discrepancy
between the size of the upper jaw relative to the the lower jaw. Malocclusion of
some sort is so common that the concept of an "ideal occlusion" is called into
question, and it can be considered "normal to be abnormal". An an occlusal
interference may refer to a problem which interferes with the normal path of the
bite, and is usually used to describe a localized problem with the position or
shape of a single tooth or group of teeth. A premature contact is a term that
refers to one part of the bite meeting sooner than other parts, meaning that the
rest of the teeth meet later or are held open. E.g. a new dental restoration on
a tooth (e.g. a crown) which has a slightly different shape or position to the
original tooth may contact too soon in the bite. A deflective interference
refers to a interference with the bite that changes the normal path of the bite.
A common example of a deflective is an over-erupted upper wisdom tooth, often
because the lower wisdom tooth has been removed. In this example, when the jaws
are brought together, the lower back teeth contact the prominent wisdom tooth
before the other teeth, and the lower jaw has to move forward to get the rest of
the teeth to meet. The difference between a premature contact and a deflective
interference is that the latter implies a dynamic abnormality in the
bite.
Historically, many believed that problems with the bite were
the sole cause for bruxism. It was often claimed that a person would grind at
the interefering area in a subconscious, instinctive attempt to wear this down
and "self equiliberate" their occlusion. However, occlusal interferences are
extremely common and usually do not cause any problems. It is unclear whether
people with bruxism tend to notice problems with the bite because of their
clenching and grinding habit, or whether these act as a causative factor in the
development of the condition. In sleep bruxism especially, there is no evidence
that removal of occlusal intereferences has any impact on the condition. People
with no teeth at all, who wear dentures can still suffer from bruxism, (although
dentures too often change the original bite). Most modern sources state that
there is no relationship, or at most a minimal relationship, between bruxism and
occlusal factors in adults. The findings of one study, which used self reported
tooth grinding rather than clinical examination to detect bruxism, suggested
that there may be more of a relationship between occlusal factors and bruxism in
children. However, the role of occlusal factors in bruxism cannot be completely
discounted due to insufficient evidence and problems with the design of
studies.
Other
possible causes
The
following factors may be associated with bruxism:
Rarely,
neurological or psychiatric disorders may show bruxism as a
feature.
Disturbed sleep patterns and other sleep disorders (obstructive
sleep apnea, hypopnea, snoring, moderate daytime sleepiness,
insomnia)
Eating disorders,
Reduction in salivary
flow,
Hypersensitivity of the dopamine receptors in the brain
Disorders
such as Huntington's and Parkinson's diseases- (possibly due to long term
therapy with levodopa causing a dopaminergic
dysfunction)
Obsessive–compulsive disorder
Eustachian tube
dysfunction
Cerebral palsy.
Acrodynia
Torus mandibularis
Mental
retardation, particularly children.
Oromandibular dystonia,
Rett
syndrome,
Dyskinesias.
Down syndrome.
Autism[8]
coma, brain
injury
trauma,
Sequelae
Bruxism is
usually detected because of the effects of the process (most commonly tooth wear
and pain), rather than the process itself. The large forces that can be
generated during bruxism can have detrimental effects on the three components of
masticatory system (the teeth, the periodontium and the articulation of the
mandible with the skull). The muscles of mastication that act to move the jaw
can also be affected since they are being utilized over and above of normal
function.
Tooth wear
Tooth wear
caused by tooth to tooth contact is termed attrition. This is the most usual
type of tooth wear that occurs in bruxism, and affects the occlusal surface (the
biting surface) of the teeth. The exact location and pattern of attrition
depends on how the bruxism occurs, e.g. side to side grinding on the back teeth
will flatten the biting surfaces of the back teeth, or posturing the mandible
forwards and grinding on the incisor teeth will preferentially wear these
(posturing may not be involved if there is an existing edge to edge, class III
incisal relationship).
Abfraction
is another type of tooth wear that is postulated to occur with bruxism, although
some still argue whether this type of tooth wear is a reality. Abfraction
cavities are said to occur usually on the facial aspect of teeth, in cervical
region as V-shaped defects caused by flexing of the tooth under occlusal forces.
It is argued that similar lesions can be caused by long term forceful
toothbrushing. However, the fact that the cavities are V-shaped does not suggest
that the damage is caused by toothbush abrasion, and that some abfraction
cavities occur below the level of the gumline, i.e. in an area shielded from
toothbrush abrasion, supports the validity of this mechanism of tooth
wear.
In addition
to attrition, erosion is said to synergistically contribute to tooth wear in
some bruxists, according to some sources.
Once tooth
wear progresses through the enamel layer, the exposed dentin layer is softer and
more vulnerable to wear and tooth decay. If enough of the tooth is worn away or
decayed, the tooth will effectively be weakened, and may fracture under the
increased forces that occur in bruxism.
In a typical
case involving lateral motion (side to side grinding), the canines and incisors
of the opposing arches are moved against each other laterally, i.e., with a
side-to-side action by the medial pterygoid muscles that lie medial to the
temporomandibular joints bilaterally. This movement abrades tooth structure and
can lead to the wearing down of the incisal edges of the teeth. People with
bruxism may also grind their posterior teeth, which wears down the cusps of the
occlusal surface. Most (but not all) bruxism includes clenching force provided
by masseter and temporalis muscle groups; but some bruxers clench and grind
front teeth only, which involves neither masseter nor temporalis muscle
groups.
Tooth
mobility
The view
that occlusal trauma (as may occur during bruxism) is a causative factor in
gingivitis and periodontitis is not widely accepted. It is thought that the
periodontal ligament may respond to increased occlusal (biting) forces by
resorbing some of the bone of the alveolar crest, which may result in increased
tooth mobility, however these changes are reversible if the occlusal force is
reduced. Tooth movement that occurs during occlusal loading is sometimes termed
fremitus. It is generally accepted that increased occlusal forces are able to
increase the rate of progression of pre-existing periodontal disease (gum
disease), however the main stay treatment is plaque control rather than
elaborate occlusal adjustments. It is also generally accepted that periodontal
disease is a far more common cause of tooth mobility and pathological tooth
migration than any influence of bruxism, although bruxism may much less commonly
be involved in both.
Pain
Most people
with bruxism will not experience any pain. Furthermore, the presence or degree
of pain does not necessarily correlate with the severity of grinding or
clenching that is occurring. The pain in the muscles of mastication caused by
bruxism can be likened to muscle pain that occurs after exercise. The forces
exerted are more than the periodontal ligament is biologically intended to
handle, and so inflammtion results. The tooth may become sore to bite on, and
further, tooth wear may reduce the insulating width of enamel and dentin that
protects the pulp of the tooth and result in hypersensitivity, e.g. to cold
stimuli.
The
relationship of bruxism with temporomandibular joint disorder (TMD, or
temporomandibular pain dysfunction syndrome) is debated. Many suggest that sleep
bruxism can be a causative or contributory factor to pain symptoms in TMD.
Indeed, the symptoms of TMD overlap with those of bruxism. Others suggest that
there is no strong association between TMD and bruxism. A systematic review
investigating the possible relationship concluded that when self reported
bruxism is used to diagnose bruxism, there is a positive association with TMD
pain, and when more strict diagnostic criteria for bruxism are used, the
association with TMD symptoms is much lower.
may lead to
myofascial muscle pain, temporomandibular joint dysfunction</ref> and
headaches. In severe, chronic cases, bruxism can lead to arthritis of the
temporomandibular joints.
Diagnosis
A diagnosis
of bruxism is usually made clinically. Bruxism is not the only cause of tooth
wear, making it difficult to diagnose by visual evidence alone. Abraded teeth
are usually brought to the patient's attention during a routine dental
examination.
The most
reliable diagnostic technique is measuring EMG (electromyography). These
measurements pick up electrical signals from the chewing muscles (masseter and
temporalis). This method is commonly used in sleep labs. Three forms of EMG
measurement are available outside of sleep labs.
"Bedside"
EMG units are similar to those used by sleep labs. These units pick up their
signals from facial muscles through wires connecting the bedside unit to
electrodes that are adhesively attached to the user's face. TENS electrodes or
ECG electrodes may be used.
A
biofeedback headband may be used in silent mode to record the total number of
clenching incidents and the total clenching time each night. These two numbers
easily distinguish clenching from rhythmic grinding and allow dentists to
quantify severity levels. Biofeedback headbands do not require adhesive
electrodes or wires attached to the face. They do not record the exact time,
duration, and strength of each clenching incident as bedside EMG monitors
do.
Bedside EMG
units and biofeedback headbands can both be used either as a diagnosis
measurement or in biofeedback mode as a treatment to help patients reduce their
bruxism.
"Disposable"
EMG monitors adhesively mount to the side of the face over the masseter muscle.
They monitor one night and provide a single-digit measure of bruxism
severity.
ICSD-R
Diagnostic criteria
The ICSD-R
listed diagnostic criteria for sleep bruxism. The minimal criteria include both
of the following criteria:
A. symptom of tooth-grinding or tooth-clenching
during sleep, and
B. One or more of the following: Abnormal tooth
wear
Grinding sounds
Discomfort of the jaw
muscles
With the
following criteria supporting the diagnosis:
C. polysomnography shows both:
Activity of jaw muscles during sleep
No associated epileptic
activity
D. No other
medical or mental disorders (e.g., sleep-related epilepsy, which may cause
abnormal movement during sleep).
E. The presence of other sleep disorders
(e.g., obstructive sleep apnea syndrome).
Management
Treatment
for bruxism revolves around repairing the damage to teeth that has already
occurred, and also often attempting to prevent further damage by various
methods, but there is no widely accepted, best treatment. Since bruxism is not
life threatening, and there is little evidence of the efficacy of any treatment,
it has been recommended that only conservative treatment which is reversible and
that carries low risk of morbidity should be used.
Repairing
the damage to teeth
Bruxism can
cause significant tooth wear if it is severe, and sometimes dental restorations
(crowns, fillings etc) are damaged or lost, sometimes repeatedly. Most dentists
therefore prefer to keep dental treatment in people with bruxism very simple and
only carry it out when essential, since any dental work is likely to fail in the
long term. Dental implants and complex bridgework for example are relatively
contraindicated in bruxists. In the case of crowns, the strength of the
restoration becomes more important, sometimes at the cost of esthetic
considerations. E.g. a full coverage gold crown, which has a degree of
flexibility and also involves less removal (and therefore less weakening) of the
underlying natural tooth may be more appropriate than other types of crown which
are primarily designed for esthetics rather than durability. Porcelain veneers
on the incisors are particularly vulnerable to damage, and sometimes a crown can
be perforated by occlusal wear.
Dental
guards and occlusal splints
A lower,
full coverage occlusal splint.
An upper, full coverage occlusal splint.
A dental guard or
splint can reduce tooth abrasion. Dental guards are devided into partial or
full-coverage splints and are typically made of plastic and fit over some or all
of upper and/or lower teeth. The guard protects the teeth from abrasion and can
reduce muscle strain by allowing the upper and lower jaw to move easily with
respect to each other. Treatment goals include: constraining the bruxing pattern
to avoid damage to the temporomandibular joints; stabilizing the occlusion by
minimizing gradual changes to the positions of the teeth, preventing tooth
damage and revealing the extent and patterns of bruxism through examination of
the markings on the splint's surface. A dental guard is typically worn during
every night's sleep on a long-term basis. However, a meta-analysis of occlusal
splints (dental guards) used for this purpose concluded "There is not enough
evidence to state that the occlusal splint is effective for treating sleep
bruxism."
A
repositioning splint is designed to change the patient's occlusion, or bite. The
efficacy of such devices is debated. Some writers propose that irreversible
complications can result from the long-term use of mouthguards and repositioning
splints. Randomly controlled trials with these type devices generally show no
benefit over other therapies. Another partial splint option is an NTI
(nociceptive trigeminal inhibitor) dental guard. Nociceptor nerves sense and
respond to pressure. The trigeminal nerve supplies the face and mouth. The NTI
appliance snaps onto the front teeth. The NTI prevents tissue damages primarily
by reducing the bite force from attempts to close the jaw normally into a
forward twisting of the lower front teeth. The intent is for the brain to
interpret the nerve sensations as undesirable, automatically and subconsciously
reducing clenching force. Patients who subconsciously clench their teeth are
clenching less, even during sleeping hours, when using an NTI device. The NTI
device must be fitted by a skilled and experienced practician. The NTI patients
who require ongoing follow-ups can be monitored by a general
dentist.
In a 2010
review in Journal of Orofacial Pain of 47 publications that involved 44
randomized controlled trials with a total of more than 2200 participants,
Fricton et al. concluded: "Hard stabilization appliances, when adjusted
properly, have good evidence of modest efficacy in the treatment of TMJD pain
compared to non-occluding appliances and no treatment. Other types of
appliances, including soft stabilization appliances, anterior positioning
appliances, and anterior bite appliances, have some RCT evidence of efficacy in
reducing TMJD pain. However, the potential for adverse events with these
appliances is higher and suggests the need for close monitoring in their
use."
Psychosocial
interventions
Given the
strong association between awake bruxism and psychosocial factors (the
relationship between sleep bruxism and psychosocial factors being unclear), the
role of psychosocial interventions could be argued to be central to the
management. The most simple form of treatment is therefore reassurance that the
condition does not represent a serious disease, which may act to alleviate
contributing stress. Other interventions include relaxation techniques, stress
management and hypnosis (self hypnosis or with a hypnotherapist). Cognitive
behavioral therapy has been recommended by some for treatment of
bruxism.
Medication
Many
different medications have been used to treat bruxism, including
benzodiazepines, anticonvulsants, beta blockers, dopamine agents,
antidepressants, muscle relaxants, and others. However there is little, if any,
evidence for their respective and comparative efficacies with each other and
when compared to a placebo. A systematic review is underway to investigate the
evidence for drug treatments in sleep bruxism.
Specific
drugs which have been studied in sleep bruxism include pergolide, clonidine,
propranolol, and l-tryptophan, with some showing no effect and others appear to
have promising initial results, however it has been suggested that further
safety testing is required before any evidenced based clinical recommendations
can be made. When bruxism is related to the use of selective serotonin reuptake
inhibitors in depression, adding buspirone has been reported to resolve the side
effect.
Botox
Botulinum
toxin (Botox) has been suggested as a treatment for bruxism, however there is
only one randomized control trial which has reported that Botox reduces the
myofascial pain symptoms. This scientific study was based on thirty people with
bruxism who received Botox injections into the muscles of mastication and a
control group of people with bruxism who received placebo injections. Normally
multiple trials with larger cohorts are required to make any firm statement
about the efficacy of a treatment. In 2013, a further randomized control trial
investigating Botox in bruxism started. There is also little information
available about the safety and long term follow up of this treatment for
bruxism.
Botulinum
toxin causes muscle paralysis by inhibition of acetylcholine release at
neuromuscular junctions. Botox injections are used in bruxism on the theory that
a dilute solution of the toxin will partially paralyze the muscles and lessen
their ability to forcefully clench and grind the jaw, whilst aiming to retain
enough muscular function to enable normal activities such as talking and eating.
This treatment typically involves five or six injections into the masseter and
termporalis muscles, and less often into the lateral pterygoids, (given the
possible risk of decreasing the ability to swallow). It takes a few minutes per
side, and the patient may start feeling the effects by the next day, and may
last for about three months. Occasionally, adverse effects may occur, such as
bruising can occur, but this is quite rare. The dose of toxin used depends upon
the person, and a higher dose may be needed in people with stronger muscles of
mastication. With the temporary and partial muscle paralysis, atrophy of disuse
may occur, meaning that the future required dose may be smaller or the length of
time the effects last may be increased.
Biofeedback
Question
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The
principle behind biofeedback in treating bruxism is to automatically detect
bruxing behavior, and provide a conscious or subconscious awareness signal to
the user so that the user can decrease that behavior, preferably even while
asleep. Some clinical trials have shown nighttime biofeedback to be effective at
reducing nighttime bruxism behavior (though daytime biofeedback alone has not
been shown to be effective at altering nighttime
behavior).
The first
wearable nighttime EMG biofeedback device (the biofeedback headband) became
available in 2001. The awareness signal it provides is a sound which comes on
quietly and gradually gets louder until the clenching incident stops, or until a
maximum volume level (set by the user) is reached. Daytime practice is advised
to facilitate responding in sleep without waking.
The
biofeedback headband also tallies nightly data on the number of events that last
for at least two seconds and the total accumulated duration of those events. A
"fast-response" headband catches events that last for as little as 0.2 seconds.
Since the same muscles used in clenching are also used in yawning and
swallowing, a fast-response headband may sound during yawns and swallowing, so a
standard-response headband is better for use during sleep, and will not include
swallowing incidents in its time and clench count tallies. Studies indicate that
the reduction in bruxism available during ongoing use of nighttime biofeedback
relapses if biofeedback is discontinued, so this treatment should be considered
long-term just as mouth guards are if long-term benefit is
desired.
Another type
of wearable EMG biofeedback device became available in 2005. It uses a mild
electric shock as the biofeedback, producing an undesirable sensation intended
to interrupt bruxing. The shock current is referred to by the manufacturer as
"contingent electrical stimulation". The manufacturer's marketing literature
speaks of triggering an "inhibitory reflex", but the only inhibitory reflex from
the nerves stimulated is a pain reflex, and normally the device is not set to a
high enough level to trigger such a reflex. If the shock current is set lower so
the user can remain asleep through the shock, the response is less of a reflex
response and requires conscious or subconscious participation on the part of the
user, similar to the acoustic biofeedback headband. Some patients report
desensitizing of nerves after a night of use. Some users report referred pain
that appears to come from non-facial locations when the facial shock happens.
Bruxism reduction clinical trial results are similar to those for the
biofeedback headband. Typical consumer cost of an electric stimulation
biofeedback device is about $1000. Electric stimulation units are not available
in headband form in the US due to patents on the biofeedback headband, but
rather are arm-band mounted, with a wire that runs to a disposable three-contact
electrode which attaches adhesively to the face (typically over the masseter
muscle at the jaw joint).
The NTI
dental guard is technically also a biofeedback device (translating physical bite
force into an uncomfortable feeling in the front teeth), so it is mentioned here
as well as above in the section on dental guards and
splints.
Another type
of biofeedback therapy relies on stimulating the taste buds. The therapy
involves suspending sealed packets containing a harmless but bad-tasting
substance (e.g. hot sauce, vinegar, denatonium benzoate, etc.) between the rear
molars using an orthodontic-style appliance. Attempts to bring the teeth
together ruptures the packets, alerting the user. One major difference between
this biofeedback method and all the others is that the undesirable sensation
(taste) does not go away immediately when clenching stops. Thus this method is
more likely to wake the user.
Occlusal
adjustment/reorganization
An
alternative to simply re-actively repairing the damage to teeth and conforming
to the existing occlusal scheme, occasionally dentists will attempt to
reorganize the occlusion in the belief that this may redistribute the forces and
reduce the amount of damage inflicted on the dentition. This can be a complex
procedure, and there is much disagreement between proponents of these techniques
on most of the aspects involved. It may involve orthodontics, restorative
dentistry or even orthognathic surgery. One technique involves the "Dahl
effect", which may utilize a Dahl appliance. This is a dental appliance which is
worn over the front teeth, and holds the back teeth apart during the bite. Over
time, the back teeth erupt into the mouth further because they have no opposing
tooth to bite into. When the appliance is removed, there will be slightly more
vertical space between the front teeth since the back teeth now meet sooner.
This allows for placement of new crowns on the front teeth, when before there
would have not been enough height to place them.
Epidemiology
More data
are available for the prevalence of sleep bruxism compared to bruxism generally,
or specifically to awake bruxism. In a Scandinavian study of over 1000 people in
the general population, 27.2% reported some form of bruxism, however since many
people with bruxism are not aware of their habit, self reported tooth grinding
and clenching habits may be a poor measure of the true prevalence. The ICSD-R
states that 85-90% of the general population grind their teeth to a degree at
some point during their life, although only 5% will develop a clinical
condition. One study reported the prevalence of awake and sleep bruxism to be
20% and 8-16% respectively. Awake bruxism affects females more commonly than
males, whilst in sleep bruxism, males are as equally affected as
females.
Children are
reported to brux as commonly as adults. It is possible for sleep bruxism to
occur as early as the first year of life - after the first teeth (deciduous
incisors) erupt into the mouth, and the overall prevalence in children is about
14-20%.[19] The ICSD-R states that sleep bruxism may occur in over 50% of normal
infants. Often sleep bruxism develops during adolescence, and the prevalence in
18 to 29 year olds is about 13%. The overall prevalence in adults is reported to
be 8%, and people aver the age of 60 are less likely to be affected, with the
prevalence dropping to about 3% in this group.
History
"La
bruxomanie" (a french term roughly equivalent to bruxomania), is suggested by
Marie Pietkiewics in 1907. In 1931, Frohman first coined the term bruxism.
Occasionally recent medical publications will use the word bruxomania with
bruxism, to denote specifically bruxism that occurs whilst awake, however this
term can be considered historical and the modern equivalent would be awake
bruxism or diurnal bruxism.
Society and
culture
Clenching
the teeth is generally displayed by humans and other animals as a display of
anger, hostility or frustration. It is thought that in humans, clenching the
teeth may be an evolutionary instinct to display teeth as weapons, thereby
threaten a rival or a predator.
In the Bible
there are several references to "gnashing of teeth" (derived from the same Greek
word "brygmos" from which bruxism originates) in both the Old Testament, and the
New Testament particularly, where the phrase "wailing and gnashing of teeth" is
used to described the fate of sinners in hell (Matthew
22:13).
In the 2005
film Beowulf & Grendel, a modern reworking of the Anglo-Saxon poem Beowulf,
Selma the witch tells Beowulf that the troll's name Grendel means "grinder of
teeth", stating that "he has bad dreams", a possible allusion to Grendel
traumatically witnessing the death of his father as a child, at the hands of
King Hrothgar. The Geats (the warriors who hunt the troll) alternatively
translate the name as "grinder of men's bones" to demonize their
prey.
In rave
culture, recreational use of ecstasy causes many health problems, and bruxism is
often reported by users. Whilst dancing, it is common to use pacifiers,
lollipops or chewing gum in an attempt to reduce the damage to the teeth and to
prevent jaw pain.
refers to excessive grinding of teeth and/or excessive clenching of the jaw.
Bruxism is an oral parafunctional activity, that is to say, it is not activity
related to normal function such as eating or talking. Bruxism is a common
problem, with some sources stating that 85-90% of the general population grind
their teeth to a degree at some point during their life, although only 5% will
develop a clinical condition. Bruxism may cause minimal symptoms, and therefore
people may not be aware of the condition. Several symptoms are commonly
associated, including hypersensitive teeth, aching jaw muscles and headaches.
Bruxism may also cause tooth wear, or even cause teeth to break and dental
restorations (e.g. crowns and fillings) to be repeatedly lost or
damaged.
There
are two main types of bruxism, namely bruxism which occurs during sleep (sleep
bruxism) and bruxism which occurs during wakefulness (awake bruxism). The damage
to the teeth is similar in both types, but the symptoms of sleep bruxism are
usually worst upon waking and then slowly get better over the day, and the
symptoms of awake bruxism may not be present at all upon waking, and then slowly
get worse over the day. The causes of bruxism are not totally understood, but
probably involves multiple factors. Awake bruxism is thought to have different
causes to sleep bruxism, and is more common in females whereas males and females
are affected in equal proportions by sleep bruxism. There are several treatments
in use, although there is very little evidence for any particular treatment in
the management of bruxism
Bruxism is
derived from the Greek word βρυγμός (brygmós), meaning "gnashing of teeth".
People who suffer with bruxism may also be called "bruxists", and the act itself
"to brux". There is no widely accepted definition of bruxism, but some suggested
definitions include:
"A
movement disorder of the masticatory system charactized by teeth grinding and
clenching during sleep as well as wakefulness."
"Non-functional contact of the mandibular and maxillary teeth
resulting in clenching or tooth grinding due to repetitive, unconscious
contraction of the masseter and temporalis muscles."
"Parafunctional grinding of teeth or an oral habit consisting
of involuntary rhythmic or spasmodic non functional gnashing, grinding or
clenching of teeth in other than chewing movements of the mandible which may
lead to occlusal trauma."
"Periodic repetitive clenching or rhythmic forceful grinding of
the teeth."
Classification by temporal pattern
Bruxism can
be subdivided into two types based upon when the parafunctional activity occurs
- during sleep ("sleep bruxism"), or whilst awake ("awake bruxism"). This
distinction is most widely referred to since sleep bruxism generally has
different causes to awake bruxism, although the affects of condition on the
teeth are the same. The treatment is also often dependent upon whether the
bruxism happens during sleep or whilst awake. E.g., an occlusal splint worn
during sleep in a person who only bruxes when they are awake will probably have
no benefit. Awake bruxism is sometimes abbreviated to AB, and is also termed
"diurnal bruxism", DB, or "daytime bruxing". Sleep bruxism is sometimes
abbreviated to SB, and is also termed "sleep-related bruxism", "nocturnal
bruxism", or "nocturnal tooth grinding"). According to the International
Classification of Sleep Disorders revised edition (ICSD-R), the term "sleep
bruxism" is the most appropriate since this type occurs during sleep
specifically rather than being associated with a particular time of day, i.e. if
a person with sleep bruxism were to sleep during the day and stay awake at night
then the condition would not occur during the night but during the day. The
ICDS-R defined sleep bruxism as "a stereotyped movement disorder characterized
by grinding or clenching of the teeth during sleep", classifiying it as a
parasomnia. The second edition (ICSD-2) however reclassified bruxism to a "sleep
related movement disorder" rather than a parasomnia.
Classification by cause
Alternatively, bruxism can be divided into primary bruxism
(also termed "idiopathic bruxism"), where the disorder is not related to any
other medical condition, or secondary bruxism where the disorder is associated
with other medical conditions. Secondary bruxism includes iatrogenic causes,
such as the side effect of prescribed medications. Another source divides the
causes of bruxism into 3 groups, namely central or pathophysiological factors,
psychosocial factors and peripheral factors. The World Health Organization's
International Classification of Diseases 10th revision does not have an entry
called bruxism, instead listing "tooth grinding" under somatoform disorders. To
describe bruxism as a purely somatoform disorder does not reflect the
mainstream, modern view of this condition
Classification by severity
The ICSD-R
described three different severities of sleep bruxism, defining mild as
occurring less than nightly, with no damage to teeth or psychosocial impairment;
moderate as occurring nightly, with mild impairment of psychosocial functioning;
and severe as occuring nightly, and with damage to the teeth, tempormandibular
disorders and other physical injuries, and severe psychosocial
impairment.
Classification by duration
The ICSD-R
also described three different types of sleep bruxism according to the duration
the condition is present, namely acute, which lasts for less than 1 week;
subacute, which lasts for more than a week and less than a month; and chronic
which lasts for over a month.
Signs and
symptoms
Most people
who brux are unaware of the problem, either because there are no symptoms, or
because the symptoms are not understood to be associated with a clenching and
grinding problem. Some individuals clench without significant lateral
movements.
The symptoms
of sleep bruxism are usually most intense immediately after waking, and then
slowly get better, and the symptoms of a bruxing habit which occurs mainly while
awake tend to slowly get worse throughout the day, and may not be present upon
waking.
Long
term effects of severe bruxism on an anterior tooth, revealing the dentin and
pulp which are normally hidden by enamel
Bruxism may cause a variety of
signs and symptoms, including:
Excessive tooth wear, particularly attrition,
but also possibly abfraction.
Tooth fractures, and repeated failure of
dental restorations (fillings, crowns, etc.),
Hypersensitive teeth, (e.g.
sensitivity when drinking a cold liquid)
Inflammation of the periodontal
ligament of teeth, which may make them sore to bite on, and possibly also a
degree of loosening of the teeth,[8]
A grinding noise during sleep (in sleep
bruxism), sometimes detected by a partner or a parent. This noise can be
surprisingly loud and unpleasant, and can wake a sleeping partner.
Cheek
biting (which may manifest as morsicatio buccarum and/or linea alba), and/or lip
biting, (other parafunctional habits which may occur together with
bruxism)
A burning sensation on the tongue (see: glossodynia), possibly
related to a coexistent "tongue thrusting" parafunctional
habit.
Indentations of the teeth in the tongue ("crenated tongue" or
"scalloped tongue"),
Hypertrophy of the muscles of mastication (increase in
the size of the muscles that move the jaw), particularly the masseter
muscle
Tenderness, pain or fatigue of the muscles of mastication, which may
get worse during chewing or other jaw movement,
Trismus (restricted mouth
opening),
Pain or tenderness of the temporomandibular joints, which may
manifest as preauricular pain, or pain referred to the ear
(otalgia).
Headaches, or other facial pain including atypical facial
pain,
Causes
The cause of
bruxism is largely unknown, but it is generally accepted to have multiple
possible causes. Bruxism is a parafunctional activity, but it is debated whether
this represents a subconscious habit or is entirely involuntary. Awake bruxism
is thought to be usually semivoluntary, and often associated with stress caused
by family responsibilities or work pressures. There is evidence that sleep
bruxism is caused by mechanisms related to the central nervous system, involving
sleep arousal and neurotransmitter abnormalities. Underlying these factors may
be psychosocial factors including daytime stress which is disrupting peaceful
sleep. Awake bruxism usually involves clenching, (sometimes the term "awake
clenching" is used instead of awake bruxism), but also possibly grinding, and is
often associated with other semivoluntary oral habits such as cheek biting, nail
biting, chewing on a pen or pencil absent mindedly, or tongue trusting (where
the tongue is pushed against the front teeth forcefully). Sleep bruxism is
mainly characterized by "rhythmic masticatory muscle activity" (RMMA) at a
frequency of about once per second, and also with occasional tooth grinding. It
has been shown that the majority of sleep bruxism episodes occur during periods
of sleep arousal.
Reflex
activities happen reliably in response to a stimulus, without involvement of
subconscious brain activity. Chewing and clenching are complex neuromuscular
activities that can be controlled either by subconscious processes or by
conscious processes within the brain. During sleep, (and for some during waking
hours while conscious attention is distracted) subconscious processes can run
unchecked, allowing bruxism to occur.[citation needed] Some bruxism activity is
rhythmic with bite force pulses of tenths of a second (like chewing), and some
have longer bite force pulses of 1 to 30 seconds
(clenching).
Bruxism can
also be regarded as a disorder of repetitive, unconscious contraction of a
complex set of myofacial muscles; this typically involves the masseter and
anterior temporalis (the large outer muscles that clench), and the lateral
pterygoids, relatively small bilateral muscles that act together to perform
sideways grinding.
The jaw
clenching that is often part of bruxism can be an unconscious neuromuscular
daytime activity, which should be treated as well, usually through physical
therapy (recognition and stress response reduction)
Psychosocial
factors
Many studies
have reported significant psychosocial risk factors for bruxism, particularly a
stressful lifestyle, and this evidence is growing, but still not conclusive. It
has been reported that persons with bruxism respond differently to depression,
hostility and stress compared to people without bruxism. Stress has a stronger
relationship to awake bruxism, but the role of stress in sleep bruxism is less
clear, with some stating that there is no evidence for a relationship with sleep
bruxism.[16] However, children with sleep bruxism have been shown to have
greater levels of anxiety than other children. People aged 50 with bruxism are
more likely to be single and have a high level of education. Work related stress
and irregular work shifts may also be involved.[18] Animal studies have also
suggested a link between bruxism and psychosocial factors. Rosales et al.
electrocuted lab rats, and then observed high levels of bruxism-like muscular
activity in rats that were allowed to watch this treatment compared to rats that
did not see it. They proposed that the rats who witnessed the electrocution of
other rats were under emotional stress which may have caused the bruxism like
behaviour.
Genetic
Some
research suggests that there may be a degree of inherited susceptibility to
develop sleep bruxism. 21-50% of people with sleep bruxism have a direct family
member who had sleep bruxism during childhood, suggesting that there are genetic
factors involved,[19] although no genetic markers have yet been identified.
Offspring of people who have sleep bruxism are more likely to also have sleep
bruxism than children of people who do not have bruxism, or people with awake
bruxism rather than sleep bruxism.
Medications
Certain
drugs, including both prescribed and recreational drugs are thought to cause
bruxism to develop, however others argue that there is insufficient evidence to
draw conclusion between the effect of any medication and bruxism. Examples
include dopamine agonists, dopamine antagonists, tricyclic antidepressants,
selective serotonin reuptake inhibitors, alcohol, cocaine, amphetamines
(including those taken for medical reasons). In some reported cases when bruxism
is thought to have been initiated by selective serotonin reuptake inhibitors,
decreasing the dose resolved the side effect.
Specific
examples include levodopa (used in Parkinson's disease),
methylenedioxymethamphetamine (MDMA, ecstasy), methylenedioxyamphetamine (MDA),
methylphenidate, and gamma-hydroxybutyric acid (GHB) and similar
gamma-aminobutyric acid-inducing analogues such as phenibut. Bruxism can also be
exacerbated by excessive consumption of caffeine such as coffee, tea or
chocolate. Nicotine stimulates release of dopamine, which is postulated to
explain why bruxism is twice as common in smokers compared to non
smokers.
Occlusal
interference
Occlusion is
defined most simply as "contacts between teeth", and refers to the meeting of
teeth during biting and grinding. The term does not imply any disease.
Malocclusion is a medical term referring to less than ideal positioning of the
upper teeth relative to the lower teeth, which can occur both when the upper jaw
is ideally proportioned to the lower jaw, or where there is a discrepancy
between the size of the upper jaw relative to the the lower jaw. Malocclusion of
some sort is so common that the concept of an "ideal occlusion" is called into
question, and it can be considered "normal to be abnormal". An an occlusal
interference may refer to a problem which interferes with the normal path of the
bite, and is usually used to describe a localized problem with the position or
shape of a single tooth or group of teeth. A premature contact is a term that
refers to one part of the bite meeting sooner than other parts, meaning that the
rest of the teeth meet later or are held open. E.g. a new dental restoration on
a tooth (e.g. a crown) which has a slightly different shape or position to the
original tooth may contact too soon in the bite. A deflective interference
refers to a interference with the bite that changes the normal path of the bite.
A common example of a deflective is an over-erupted upper wisdom tooth, often
because the lower wisdom tooth has been removed. In this example, when the jaws
are brought together, the lower back teeth contact the prominent wisdom tooth
before the other teeth, and the lower jaw has to move forward to get the rest of
the teeth to meet. The difference between a premature contact and a deflective
interference is that the latter implies a dynamic abnormality in the
bite.
Historically, many believed that problems with the bite were
the sole cause for bruxism. It was often claimed that a person would grind at
the interefering area in a subconscious, instinctive attempt to wear this down
and "self equiliberate" their occlusion. However, occlusal interferences are
extremely common and usually do not cause any problems. It is unclear whether
people with bruxism tend to notice problems with the bite because of their
clenching and grinding habit, or whether these act as a causative factor in the
development of the condition. In sleep bruxism especially, there is no evidence
that removal of occlusal intereferences has any impact on the condition. People
with no teeth at all, who wear dentures can still suffer from bruxism, (although
dentures too often change the original bite). Most modern sources state that
there is no relationship, or at most a minimal relationship, between bruxism and
occlusal factors in adults. The findings of one study, which used self reported
tooth grinding rather than clinical examination to detect bruxism, suggested
that there may be more of a relationship between occlusal factors and bruxism in
children. However, the role of occlusal factors in bruxism cannot be completely
discounted due to insufficient evidence and problems with the design of
studies.
Other
possible causes
The
following factors may be associated with bruxism:
Rarely,
neurological or psychiatric disorders may show bruxism as a
feature.
Disturbed sleep patterns and other sleep disorders (obstructive
sleep apnea, hypopnea, snoring, moderate daytime sleepiness,
insomnia)
Eating disorders,
Reduction in salivary
flow,
Hypersensitivity of the dopamine receptors in the brain
Disorders
such as Huntington's and Parkinson's diseases- (possibly due to long term
therapy with levodopa causing a dopaminergic
dysfunction)
Obsessive–compulsive disorder
Eustachian tube
dysfunction
Cerebral palsy.
Acrodynia
Torus mandibularis
Mental
retardation, particularly children.
Oromandibular dystonia,
Rett
syndrome,
Dyskinesias.
Down syndrome.
Autism[8]
coma, brain
injury
trauma,
Sequelae
Bruxism is
usually detected because of the effects of the process (most commonly tooth wear
and pain), rather than the process itself. The large forces that can be
generated during bruxism can have detrimental effects on the three components of
masticatory system (the teeth, the periodontium and the articulation of the
mandible with the skull). The muscles of mastication that act to move the jaw
can also be affected since they are being utilized over and above of normal
function.
Tooth wear
Tooth wear
caused by tooth to tooth contact is termed attrition. This is the most usual
type of tooth wear that occurs in bruxism, and affects the occlusal surface (the
biting surface) of the teeth. The exact location and pattern of attrition
depends on how the bruxism occurs, e.g. side to side grinding on the back teeth
will flatten the biting surfaces of the back teeth, or posturing the mandible
forwards and grinding on the incisor teeth will preferentially wear these
(posturing may not be involved if there is an existing edge to edge, class III
incisal relationship).
Abfraction
is another type of tooth wear that is postulated to occur with bruxism, although
some still argue whether this type of tooth wear is a reality. Abfraction
cavities are said to occur usually on the facial aspect of teeth, in cervical
region as V-shaped defects caused by flexing of the tooth under occlusal forces.
It is argued that similar lesions can be caused by long term forceful
toothbrushing. However, the fact that the cavities are V-shaped does not suggest
that the damage is caused by toothbush abrasion, and that some abfraction
cavities occur below the level of the gumline, i.e. in an area shielded from
toothbrush abrasion, supports the validity of this mechanism of tooth
wear.
In addition
to attrition, erosion is said to synergistically contribute to tooth wear in
some bruxists, according to some sources.
Once tooth
wear progresses through the enamel layer, the exposed dentin layer is softer and
more vulnerable to wear and tooth decay. If enough of the tooth is worn away or
decayed, the tooth will effectively be weakened, and may fracture under the
increased forces that occur in bruxism.
In a typical
case involving lateral motion (side to side grinding), the canines and incisors
of the opposing arches are moved against each other laterally, i.e., with a
side-to-side action by the medial pterygoid muscles that lie medial to the
temporomandibular joints bilaterally. This movement abrades tooth structure and
can lead to the wearing down of the incisal edges of the teeth. People with
bruxism may also grind their posterior teeth, which wears down the cusps of the
occlusal surface. Most (but not all) bruxism includes clenching force provided
by masseter and temporalis muscle groups; but some bruxers clench and grind
front teeth only, which involves neither masseter nor temporalis muscle
groups.
Tooth
mobility
The view
that occlusal trauma (as may occur during bruxism) is a causative factor in
gingivitis and periodontitis is not widely accepted. It is thought that the
periodontal ligament may respond to increased occlusal (biting) forces by
resorbing some of the bone of the alveolar crest, which may result in increased
tooth mobility, however these changes are reversible if the occlusal force is
reduced. Tooth movement that occurs during occlusal loading is sometimes termed
fremitus. It is generally accepted that increased occlusal forces are able to
increase the rate of progression of pre-existing periodontal disease (gum
disease), however the main stay treatment is plaque control rather than
elaborate occlusal adjustments. It is also generally accepted that periodontal
disease is a far more common cause of tooth mobility and pathological tooth
migration than any influence of bruxism, although bruxism may much less commonly
be involved in both.
Pain
Most people
with bruxism will not experience any pain. Furthermore, the presence or degree
of pain does not necessarily correlate with the severity of grinding or
clenching that is occurring. The pain in the muscles of mastication caused by
bruxism can be likened to muscle pain that occurs after exercise. The forces
exerted are more than the periodontal ligament is biologically intended to
handle, and so inflammtion results. The tooth may become sore to bite on, and
further, tooth wear may reduce the insulating width of enamel and dentin that
protects the pulp of the tooth and result in hypersensitivity, e.g. to cold
stimuli.
The
relationship of bruxism with temporomandibular joint disorder (TMD, or
temporomandibular pain dysfunction syndrome) is debated. Many suggest that sleep
bruxism can be a causative or contributory factor to pain symptoms in TMD.
Indeed, the symptoms of TMD overlap with those of bruxism. Others suggest that
there is no strong association between TMD and bruxism. A systematic review
investigating the possible relationship concluded that when self reported
bruxism is used to diagnose bruxism, there is a positive association with TMD
pain, and when more strict diagnostic criteria for bruxism are used, the
association with TMD symptoms is much lower.
may lead to
myofascial muscle pain, temporomandibular joint dysfunction</ref> and
headaches. In severe, chronic cases, bruxism can lead to arthritis of the
temporomandibular joints.
Diagnosis
A diagnosis
of bruxism is usually made clinically. Bruxism is not the only cause of tooth
wear, making it difficult to diagnose by visual evidence alone. Abraded teeth
are usually brought to the patient's attention during a routine dental
examination.
The most
reliable diagnostic technique is measuring EMG (electromyography). These
measurements pick up electrical signals from the chewing muscles (masseter and
temporalis). This method is commonly used in sleep labs. Three forms of EMG
measurement are available outside of sleep labs.
"Bedside"
EMG units are similar to those used by sleep labs. These units pick up their
signals from facial muscles through wires connecting the bedside unit to
electrodes that are adhesively attached to the user's face. TENS electrodes or
ECG electrodes may be used.
A
biofeedback headband may be used in silent mode to record the total number of
clenching incidents and the total clenching time each night. These two numbers
easily distinguish clenching from rhythmic grinding and allow dentists to
quantify severity levels. Biofeedback headbands do not require adhesive
electrodes or wires attached to the face. They do not record the exact time,
duration, and strength of each clenching incident as bedside EMG monitors
do.
Bedside EMG
units and biofeedback headbands can both be used either as a diagnosis
measurement or in biofeedback mode as a treatment to help patients reduce their
bruxism.
"Disposable"
EMG monitors adhesively mount to the side of the face over the masseter muscle.
They monitor one night and provide a single-digit measure of bruxism
severity.
ICSD-R
Diagnostic criteria
The ICSD-R
listed diagnostic criteria for sleep bruxism. The minimal criteria include both
of the following criteria:
A. symptom of tooth-grinding or tooth-clenching
during sleep, and
B. One or more of the following: Abnormal tooth
wear
Grinding sounds
Discomfort of the jaw
muscles
With the
following criteria supporting the diagnosis:
C. polysomnography shows both:
Activity of jaw muscles during sleep
No associated epileptic
activity
D. No other
medical or mental disorders (e.g., sleep-related epilepsy, which may cause
abnormal movement during sleep).
E. The presence of other sleep disorders
(e.g., obstructive sleep apnea syndrome).
Management
Treatment
for bruxism revolves around repairing the damage to teeth that has already
occurred, and also often attempting to prevent further damage by various
methods, but there is no widely accepted, best treatment. Since bruxism is not
life threatening, and there is little evidence of the efficacy of any treatment,
it has been recommended that only conservative treatment which is reversible and
that carries low risk of morbidity should be used.
Repairing
the damage to teeth
Bruxism can
cause significant tooth wear if it is severe, and sometimes dental restorations
(crowns, fillings etc) are damaged or lost, sometimes repeatedly. Most dentists
therefore prefer to keep dental treatment in people with bruxism very simple and
only carry it out when essential, since any dental work is likely to fail in the
long term. Dental implants and complex bridgework for example are relatively
contraindicated in bruxists. In the case of crowns, the strength of the
restoration becomes more important, sometimes at the cost of esthetic
considerations. E.g. a full coverage gold crown, which has a degree of
flexibility and also involves less removal (and therefore less weakening) of the
underlying natural tooth may be more appropriate than other types of crown which
are primarily designed for esthetics rather than durability. Porcelain veneers
on the incisors are particularly vulnerable to damage, and sometimes a crown can
be perforated by occlusal wear.
Dental
guards and occlusal splints
A lower,
full coverage occlusal splint.
An upper, full coverage occlusal splint.
A dental guard or
splint can reduce tooth abrasion. Dental guards are devided into partial or
full-coverage splints and are typically made of plastic and fit over some or all
of upper and/or lower teeth. The guard protects the teeth from abrasion and can
reduce muscle strain by allowing the upper and lower jaw to move easily with
respect to each other. Treatment goals include: constraining the bruxing pattern
to avoid damage to the temporomandibular joints; stabilizing the occlusion by
minimizing gradual changes to the positions of the teeth, preventing tooth
damage and revealing the extent and patterns of bruxism through examination of
the markings on the splint's surface. A dental guard is typically worn during
every night's sleep on a long-term basis. However, a meta-analysis of occlusal
splints (dental guards) used for this purpose concluded "There is not enough
evidence to state that the occlusal splint is effective for treating sleep
bruxism."
A
repositioning splint is designed to change the patient's occlusion, or bite. The
efficacy of such devices is debated. Some writers propose that irreversible
complications can result from the long-term use of mouthguards and repositioning
splints. Randomly controlled trials with these type devices generally show no
benefit over other therapies. Another partial splint option is an NTI
(nociceptive trigeminal inhibitor) dental guard. Nociceptor nerves sense and
respond to pressure. The trigeminal nerve supplies the face and mouth. The NTI
appliance snaps onto the front teeth. The NTI prevents tissue damages primarily
by reducing the bite force from attempts to close the jaw normally into a
forward twisting of the lower front teeth. The intent is for the brain to
interpret the nerve sensations as undesirable, automatically and subconsciously
reducing clenching force. Patients who subconsciously clench their teeth are
clenching less, even during sleeping hours, when using an NTI device. The NTI
device must be fitted by a skilled and experienced practician. The NTI patients
who require ongoing follow-ups can be monitored by a general
dentist.
In a 2010
review in Journal of Orofacial Pain of 47 publications that involved 44
randomized controlled trials with a total of more than 2200 participants,
Fricton et al. concluded: "Hard stabilization appliances, when adjusted
properly, have good evidence of modest efficacy in the treatment of TMJD pain
compared to non-occluding appliances and no treatment. Other types of
appliances, including soft stabilization appliances, anterior positioning
appliances, and anterior bite appliances, have some RCT evidence of efficacy in
reducing TMJD pain. However, the potential for adverse events with these
appliances is higher and suggests the need for close monitoring in their
use."
Psychosocial
interventions
Given the
strong association between awake bruxism and psychosocial factors (the
relationship between sleep bruxism and psychosocial factors being unclear), the
role of psychosocial interventions could be argued to be central to the
management. The most simple form of treatment is therefore reassurance that the
condition does not represent a serious disease, which may act to alleviate
contributing stress. Other interventions include relaxation techniques, stress
management and hypnosis (self hypnosis or with a hypnotherapist). Cognitive
behavioral therapy has been recommended by some for treatment of
bruxism.
Medication
Many
different medications have been used to treat bruxism, including
benzodiazepines, anticonvulsants, beta blockers, dopamine agents,
antidepressants, muscle relaxants, and others. However there is little, if any,
evidence for their respective and comparative efficacies with each other and
when compared to a placebo. A systematic review is underway to investigate the
evidence for drug treatments in sleep bruxism.
Specific
drugs which have been studied in sleep bruxism include pergolide, clonidine,
propranolol, and l-tryptophan, with some showing no effect and others appear to
have promising initial results, however it has been suggested that further
safety testing is required before any evidenced based clinical recommendations
can be made. When bruxism is related to the use of selective serotonin reuptake
inhibitors in depression, adding buspirone has been reported to resolve the side
effect.
Botox
Botulinum
toxin (Botox) has been suggested as a treatment for bruxism, however there is
only one randomized control trial which has reported that Botox reduces the
myofascial pain symptoms. This scientific study was based on thirty people with
bruxism who received Botox injections into the muscles of mastication and a
control group of people with bruxism who received placebo injections. Normally
multiple trials with larger cohorts are required to make any firm statement
about the efficacy of a treatment. In 2013, a further randomized control trial
investigating Botox in bruxism started. There is also little information
available about the safety and long term follow up of this treatment for
bruxism.
Botulinum
toxin causes muscle paralysis by inhibition of acetylcholine release at
neuromuscular junctions. Botox injections are used in bruxism on the theory that
a dilute solution of the toxin will partially paralyze the muscles and lessen
their ability to forcefully clench and grind the jaw, whilst aiming to retain
enough muscular function to enable normal activities such as talking and eating.
This treatment typically involves five or six injections into the masseter and
termporalis muscles, and less often into the lateral pterygoids, (given the
possible risk of decreasing the ability to swallow). It takes a few minutes per
side, and the patient may start feeling the effects by the next day, and may
last for about three months. Occasionally, adverse effects may occur, such as
bruising can occur, but this is quite rare. The dose of toxin used depends upon
the person, and a higher dose may be needed in people with stronger muscles of
mastication. With the temporary and partial muscle paralysis, atrophy of disuse
may occur, meaning that the future required dose may be smaller or the length of
time the effects last may be increased.
Biofeedback
Question
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The
principle behind biofeedback in treating bruxism is to automatically detect
bruxing behavior, and provide a conscious or subconscious awareness signal to
the user so that the user can decrease that behavior, preferably even while
asleep. Some clinical trials have shown nighttime biofeedback to be effective at
reducing nighttime bruxism behavior (though daytime biofeedback alone has not
been shown to be effective at altering nighttime
behavior).
The first
wearable nighttime EMG biofeedback device (the biofeedback headband) became
available in 2001. The awareness signal it provides is a sound which comes on
quietly and gradually gets louder until the clenching incident stops, or until a
maximum volume level (set by the user) is reached. Daytime practice is advised
to facilitate responding in sleep without waking.
The
biofeedback headband also tallies nightly data on the number of events that last
for at least two seconds and the total accumulated duration of those events. A
"fast-response" headband catches events that last for as little as 0.2 seconds.
Since the same muscles used in clenching are also used in yawning and
swallowing, a fast-response headband may sound during yawns and swallowing, so a
standard-response headband is better for use during sleep, and will not include
swallowing incidents in its time and clench count tallies. Studies indicate that
the reduction in bruxism available during ongoing use of nighttime biofeedback
relapses if biofeedback is discontinued, so this treatment should be considered
long-term just as mouth guards are if long-term benefit is
desired.
Another type
of wearable EMG biofeedback device became available in 2005. It uses a mild
electric shock as the biofeedback, producing an undesirable sensation intended
to interrupt bruxing. The shock current is referred to by the manufacturer as
"contingent electrical stimulation". The manufacturer's marketing literature
speaks of triggering an "inhibitory reflex", but the only inhibitory reflex from
the nerves stimulated is a pain reflex, and normally the device is not set to a
high enough level to trigger such a reflex. If the shock current is set lower so
the user can remain asleep through the shock, the response is less of a reflex
response and requires conscious or subconscious participation on the part of the
user, similar to the acoustic biofeedback headband. Some patients report
desensitizing of nerves after a night of use. Some users report referred pain
that appears to come from non-facial locations when the facial shock happens.
Bruxism reduction clinical trial results are similar to those for the
biofeedback headband. Typical consumer cost of an electric stimulation
biofeedback device is about $1000. Electric stimulation units are not available
in headband form in the US due to patents on the biofeedback headband, but
rather are arm-band mounted, with a wire that runs to a disposable three-contact
electrode which attaches adhesively to the face (typically over the masseter
muscle at the jaw joint).
The NTI
dental guard is technically also a biofeedback device (translating physical bite
force into an uncomfortable feeling in the front teeth), so it is mentioned here
as well as above in the section on dental guards and
splints.
Another type
of biofeedback therapy relies on stimulating the taste buds. The therapy
involves suspending sealed packets containing a harmless but bad-tasting
substance (e.g. hot sauce, vinegar, denatonium benzoate, etc.) between the rear
molars using an orthodontic-style appliance. Attempts to bring the teeth
together ruptures the packets, alerting the user. One major difference between
this biofeedback method and all the others is that the undesirable sensation
(taste) does not go away immediately when clenching stops. Thus this method is
more likely to wake the user.
Occlusal
adjustment/reorganization
An
alternative to simply re-actively repairing the damage to teeth and conforming
to the existing occlusal scheme, occasionally dentists will attempt to
reorganize the occlusion in the belief that this may redistribute the forces and
reduce the amount of damage inflicted on the dentition. This can be a complex
procedure, and there is much disagreement between proponents of these techniques
on most of the aspects involved. It may involve orthodontics, restorative
dentistry or even orthognathic surgery. One technique involves the "Dahl
effect", which may utilize a Dahl appliance. This is a dental appliance which is
worn over the front teeth, and holds the back teeth apart during the bite. Over
time, the back teeth erupt into the mouth further because they have no opposing
tooth to bite into. When the appliance is removed, there will be slightly more
vertical space between the front teeth since the back teeth now meet sooner.
This allows for placement of new crowns on the front teeth, when before there
would have not been enough height to place them.
Epidemiology
More data
are available for the prevalence of sleep bruxism compared to bruxism generally,
or specifically to awake bruxism. In a Scandinavian study of over 1000 people in
the general population, 27.2% reported some form of bruxism, however since many
people with bruxism are not aware of their habit, self reported tooth grinding
and clenching habits may be a poor measure of the true prevalence. The ICSD-R
states that 85-90% of the general population grind their teeth to a degree at
some point during their life, although only 5% will develop a clinical
condition. One study reported the prevalence of awake and sleep bruxism to be
20% and 8-16% respectively. Awake bruxism affects females more commonly than
males, whilst in sleep bruxism, males are as equally affected as
females.
Children are
reported to brux as commonly as adults. It is possible for sleep bruxism to
occur as early as the first year of life - after the first teeth (deciduous
incisors) erupt into the mouth, and the overall prevalence in children is about
14-20%.[19] The ICSD-R states that sleep bruxism may occur in over 50% of normal
infants. Often sleep bruxism develops during adolescence, and the prevalence in
18 to 29 year olds is about 13%. The overall prevalence in adults is reported to
be 8%, and people aver the age of 60 are less likely to be affected, with the
prevalence dropping to about 3% in this group.
History
"La
bruxomanie" (a french term roughly equivalent to bruxomania), is suggested by
Marie Pietkiewics in 1907. In 1931, Frohman first coined the term bruxism.
Occasionally recent medical publications will use the word bruxomania with
bruxism, to denote specifically bruxism that occurs whilst awake, however this
term can be considered historical and the modern equivalent would be awake
bruxism or diurnal bruxism.
Society and
culture
Clenching
the teeth is generally displayed by humans and other animals as a display of
anger, hostility or frustration. It is thought that in humans, clenching the
teeth may be an evolutionary instinct to display teeth as weapons, thereby
threaten a rival or a predator.
In the Bible
there are several references to "gnashing of teeth" (derived from the same Greek
word "brygmos" from which bruxism originates) in both the Old Testament, and the
New Testament particularly, where the phrase "wailing and gnashing of teeth" is
used to described the fate of sinners in hell (Matthew
22:13).
In the 2005
film Beowulf & Grendel, a modern reworking of the Anglo-Saxon poem Beowulf,
Selma the witch tells Beowulf that the troll's name Grendel means "grinder of
teeth", stating that "he has bad dreams", a possible allusion to Grendel
traumatically witnessing the death of his father as a child, at the hands of
King Hrothgar. The Geats (the warriors who hunt the troll) alternatively
translate the name as "grinder of men's bones" to demonize their
prey.
In rave
culture, recreational use of ecstasy causes many health problems, and bruxism is
often reported by users. Whilst dancing, it is common to use pacifiers,
lollipops or chewing gum in an attempt to reduce the damage to the teeth and to
prevent jaw pain.