Because there is documentation which indicates that chronic occlusal considerations are not related to mandibular parafunction such as bruxism, so it is not advisable to use irreversible management which may have deleterious effects.
BY: DR. BAHJAT ABU
DDS, CES, DSO
Before understanding the pathology of
any disorder in the human body, one
should have a good knowledge of the
The related physiology.
The interrelation with the other elements.
The biochemistry mechanism.
Bruxism can be regarded as forcible clenching or
grinding of the dentition, or a combination of both.
Clenching of the teeth is a forcible closure of the
opposing dentition in a static relationship of the
mandible to the maxilla. In either maximum
intercuspation or an eccentric positions.
Grinding of the dentition is a forcible closure of the
opposing dentition in a dynamic maxillo-mandibular
relationship as the mandible moves through various
Definition. AAOFP defined bruxism as “diurnal or nocturnal
parafunctional activity including clenching, bracing,
gnashing and grinding of the teeth.
Bruxism, diurnal or nocturnal, is considered as a
potential contributing factor to disturbances of the
Many individuals are not cognizant of their
parafunctional behaviors, because these activities are
usually subconscious, so obtaining accurate
response regarding his mandibular parafunctional
activity can be challenging.
Bruxism, as disorder of the
neuromuscular activity, may affect any
element of the masticatory system:
Regional or local pain, it may include one
or more of the muscles of mastication.
The myalgia may worsen during function.
Limitation of mouth opening could be
noticed as well as tenderness on
Wearing of the teeth, and TMJ problems.
In certain cases symptoms may involve
all the precedent elements.
Some studies demonstrate that bruxism
occur in up to 90% in the general
Other studies demonstrate that it affects
8% of the adult, 14% of the children, and
10-12% of the adolescents.
However some investigations showed
that the incidence is highest in the teens
and the forties, and that behavior
decreases with age.
Studies indicate that females report
parafunctional clenching more than
However clinical observations
demonstrate approximately an equal
Self reporting of clenching during waking
hours is about 20%.
Grinding of the teeth during sleeping
hours ranges from 6-12%.
Parafunctional behavior is performed at
a subconscious level by most individuals
so determination the actual prevalence is
The cause of bruxism still controversial.
The cause is multi factorial and
overlapping, which creates difficulties in
applying comprehensive, effective
management plan for this mandibular
para- functional behavior.
However, because the parafunctional
mandibular movements concern mainly
the neuromuscular system, so any
situation stimulating this system, at the
subconscious level, would contribute in
starting up bruxism.
Historically, occlusal interference were thought to be
the precipitating factor for bruxism, the assumption
was that the patient was working a subconscious
attempt at performing a self-equilibration or an
adjustment of his dentition to remove the occlusal
interferences, particularly with nocturnal bruxism.
Recent studies have refuted this assumption, but
other investigators have reported that patient
response to an occlusal interference, which existed,
is more significant than to an actual presence of
However, the relationship of the dentition may be a
Bruxism is considered as the most destructive
functional disorder to the dentition.
Emotional or physical stress as well as anticipating of
stress, are related to the mandibular parafunctional
Bruxist activity has been associated with sleep
It is reported that bruxism has been aggravated by
alcohol consumption and certain medication.
Occlusal interferences act as trigger factors for
Both centric and eccentric bruxism are expressions
of increased muscle tonus.
Its often said that bruxism in centric excursion
involves isotonic muscle contractions, while static
clenching in CO represent isometric activity.
But even the minute jaw movements include
changes in the muscle length, so that, clenching
involves both isotonic and isometric activity.
Any type of occlusal interference may,
when combined with psychic stress,
initiate and maintain bruxism.
Discrepancy between CR and CO is the
most common trigger factor for bruxism.
Interference in the balancing side is the
second is the second significant occlusal
Interference in the working side or
protrusive excursion may also trigger
Since bruxism is an expression of combined psychic
and occlusal factors. Bruxism may be present on the
basis of severe occlusal interference and moderate
degree of psychic or emotional tension, also it can be
the result of very severe psychic stress and very little
A force as little as1.5 gm or less is detectable by the
teeth. ( Munch and schriever ).
Bodies of 8-20 micron could be detected by some
individuals, and 60 mic were detected by all. (Kraft,
Tryde, Siirila and Lane)
A state of hyper tonicity muscles might
therefore be due to either :
CNS influence through the fusimotor
LOCAL disharmony between the
functional parts of the masticatory
The emotional influences on the muscles
of mastication is well known to clinicians.
Apprehension of dental procedures
increase muscle tone, and positioning of
the jaw accurately becomes difficult if not
Schematic representation of the
relationship of local and environmental
factors to dysfunctional disturbances of
the masticatory system.
Occlusal habits are all outlets for
emotional and psychic tension and have
no relation with occlusal disharmony as
in the case of bruxism.
The only indirect effect of occlusal
interferences is possibly an increase of
The precipitating factors of these habits (
lip, tong, cheek and fingernail biting) may
be overwork, worry, and premenstural or
other tensions having frustrations as the
Studies are focused on the nature of
nocturnal bruxism because of practical
limitations of investigating diurnal bruxist
Mandibular para functional behavior
during the sleeping hours:
RHYTHMIC, and forceful GRINDING.
PROLONGED CLENCHING; sustained
clenching can occur either in maximum
intercuspation, and /or eccentric
intercuspation anterior or lateral position.
Masticatory system is more prone to deleterious
ramification from forces generated by bruxism than
forces generated by functional tooth contact.
Duration, Frequency, and Intensity of the
mandibular parafunctional activity is of paramount
significance in contributing to the resulting effect.
Bruxist forces affect the structures of the masticatory
Dentition and their supporting tissues.
The associated musculature.
The mandibular rhythmic movements of
nocturnal bruxism reflect episodic
patterns that can occur at intermittent
25 bruxist episode per night each
episode may have duration of 8-9 sec.
Other study reported episode of 5
Total average bruxing time per period 42
sec. Other study reported 162 mint. With
different behavior from night to night.
Functional tooth contact during 24 hours
is approximately 20 minutes.
The excessive forces generated by
bruxism extends for more than 20
Nocturnal bruxism can generate greater
occlusal forces (subconscious) than
conscious effort during working hours.
One study demonstrated that 65% of
nocturnal bruxing episodes exceeded
forces generated by mastication.
The average working force that can be
delivered to a natural tooth is about 175
PSI (80 KG), 50 KG for FPD, and 10 Kg
for CD, wherever nocturnal bruxist can
increase this force 300 PSI with reported
cases of 100,000 to 175,000 PSI
Functional activity can generate tooth
contact forces about 17,200 lb/sec/day.
Para functional activity generate about
It is possible that cortical inhibitions
normally operational during the working
hours are suppressed during sleeping
hours, thereby allowing the masticatory
muscles to exert greater occlusal forces
during sleeping hours.
Forces delivered in the axe of the tooth
are better tolerated than lateral forces,
because stimulating the whole
periodontal tissues of the teeth as well
as the whole alveolar bone is less
traumatic than the lateral forces
stimulate just 1/17 of the periodontal
tissues and the alveolar bone.
Forces generated by functional tooth
contact has no pathologic effects on the
components of the masticatory system,
but forces generated by bruxism may
affect one element or more of the
Results are affected by resistance of the
host, duration, frequency and intensity of
the para functional activity.
In every individual there is a limit for
physiologic adaptation to imperfection or
disharmony in occlusal relationships.
When this limit is surpassed, either
because of increased occlusal
disharmony or increased CNS tension a
hypertonic response in the masticatory
The hypertonic response may be on the
basis of facilitation of nervous impulses
of occlusal origin and/or lowered
threshold of neuron excitability from
nervous tension or pain.
An increase in neuromuscular activity
may lead to injury to the periodontiumperiodontium or
the TMJTMJ, or may produce pain and
discomfort within the tense muscles.muscles.
Such injury or discomfort will result in
increased afferent stimuli to the nerve
center of the reflex system, with
subsequent tendency for increased
efferent activity and increased injurious
It appears that there is no acceptable
evidence to show that there is
adaptability of the TMJ in adults or even
children more than 10 years of age
beyond physiologic internal remodeling
that occurs in all living bones.
Although the joint where changed
temporarily because of the trauma from
occlusally induced displacement,
adaptive repositioning of the teeth
continued until the TMJs returned to their
Results of several studies indicate the
need for adapting the occlusion to the
joints rather than hoping for the joints to
adapt to the occlusion, at least when
considering the old TMJ.
It appears that changes which
occasionally take place in the TMJ are
the result of pathologic processes rather
than physiologic adaptation.
The entire dentition undergoes a
continuous adaptation to functional wear.
Adjustment of tooth position occurs
throughout a person’s lifetime in
response to naturally induced changed
of occlusal forces associated with wear,
in response to pathologic changes in the
support mechanism or muscle tonicity,
and following placement of restorations
and other dental procedures.
However, within the adaptive capacity of
the masticatory system, a balance of
forces is maintained.
The most clinical consequences of
trauma from bruxism is tooth wear as
reflected by localized or generalized
occlusal or incisal facets or both.
Excessive wear of the anterior teeth
result in esthetic concern and restorative
Severe wear of posterior teeth may
cause reduced vertical dimension,
mandible over-closure combined with
Other consequences from bruxism to the
dentition and supporting tissues include:
1- Thermal hypersensitivity.
2- Hyper mobility.
4- Injury to periodontal ligament.
5- Hyper cementosis.
6- Pulpitis an pulp necrosis.
Resorption of alveolar ridge has been
observed in denture wearer who
exhibited bruxist behavior.
Effect on the supporting tissues have
intimate relation with the quality of the
Tooth supra eruption can be noticed with
its alveolar bone, which create
Severe trauma may lead to resorption of
the cementum and it may extend to the
Patients with steep cusps may have
greater periodontal damage when lateral
stress was applied.
Escher and others claimed that
periodontal disease predispose an
individual to bruxism by increasing the
tonus of jaw muscles.
Movement of the teeth associated with
gingival and periodontal inflammation
may initiate occlusal interferences.
Discomfort associated with inflammation
may increase muscle tonus.
Repetitive overloading of the TMJ via the
dentition has been suggested as a factor
in osteoarthrosis of the TMJ.
Mandibular parafunctional activity is a
significant contributor to repetitive
This activity may cause pain in the TMJ
area if the health of the related tissues is
compromised. Elements may be involved
are retrodiscal, synovial, membranes of
the joint capsule and collateral ligaments
of the disc-condyle complex.
It’s suggested that clenching involving
the anterior dentition cause internal
derangement of the TMJ.
But with cusp to cusp contact during
eccentric clenching, the articular disk in
the ipsilateral TMJ concomitantly is
braced by the superior belly of the lateral
pterygoid muscle, the head of the
condyle moves into latero-trusive
direction these excessive forces on the
related ligaments of the disk-condyle
complex may compromise their structure
and cause disk displacement.
Tenderness to palpation of the
Patient may experience masticatory
muscle tightnessmuscle tightness and limited musclelimited muscle
movement on awaking.movement on awaking.
These muscle dysfunctions may create
muscular contraction so that they may
create vascular contraction, which
develops into possible inflammation,or
Because oxygen decreases in circulation it causeBecause oxygen decreases in circulation it cause
changes of pyruvic acid to lactic acid instead of citricchanges of pyruvic acid to lactic acid instead of citric
acid which will not allow ADP to go to ATP for energyacid which will not allow ADP to go to ATP for energy
formation; thus, the muscular system becomesformation; thus, the muscular system becomes
weaker and may end in possible necrosis of tissueweaker and may end in possible necrosis of tissue.
Excessive occlusion overloading, tension will
increase and accumulate in the muscles.
A fatigued muscle showed a loss of irritability due to
an accumulation of lactic acid.
Constant working of muscles, even when fatigueConstant working of muscles, even when fatigue
does not occur, may result in hypertrophydoes not occur, may result in hypertrophy.
It has been showed by Berlin and
Dessner and Monica that bruxism may
lead to chronic headache. Also the
correlation is not entirely clear, it has
been postulated by Wolff and others that
the basis for the pain or ache is the
disturbed circulation in the muscles.
Various type of headache pose very
difficult problems in differential diagnosis,
since some patients experience
headaches associated with muscle
tension in the masticatory system.
Patient arrives complaining of the
A tight sensation of the masticatoryA tight sensation of the masticatory
musclesmuscles that usually occurs onon
MyalgiaMyalgia of the masticatory muscles and
Hypersensitive teethHypersensitive teeth
Sounds generated from grinding the
teeth during sleeping hours reported by a
Clinical signs that the practitioner can
Occlusal and incisal wear of theOcclusal and incisal wear of the
Mobility of the teeth that are
Fracture of teeth as well as restorations.
Hypertrophy of the superfacial belly ofHypertrophy of the superfacial belly of
the masseter musclesthe masseter muscles as well as the
anterior temporalis muscles.temporalis muscles.
X ray shows widening of the periodontal
TendernessTenderness to palpation of the
The most obvious sign of nocturnal
bruxism is attrition of the incisal edges of
the anterior teeth and the occlusal
surface of the posterior teeth.
Abrasion during normal mastication or
oral habits characterized by facets of
opposing teeth that does not align with
each other whereas grinding of opposing
teeth during bruxism has wear facets
that do align.
One investigator suggested that the
objectives for management of bruxism
Reduction of psychological stress.
Reduction of occlusal irritations.
Cessation of neuromuscular habits.
Treatment of signs and symptoms of
Because the cause may be multifactorial,
a thorough medical and dental history
should be performed.
Direct therapeutic approach to the
dentition, musculature and
supporting structures include:
Intra oral orthosis.
Occlusal adjustmentOcclusal adjustment is indicated
only when there is obvious
deflective interference such as:
Supra erupted or mal positioned
Supra erupted of teeth opposed
Obvious working and non working
Inter occlusal appliance includes
many types, but with use limitation.
A study reported significant decrease in
nocturnal masseter activity after
Other study showed; reduced masseter
activity in 52%, increased in 20%,
unchanged in 28%.
Some other studies showed 80-90%
improvement in symptoms despite 50%
reduction in bruxing activity.
The purpose of the intra oral appliance is
a simple redistribution of the
Unloading the TMJ when the retrodiscal
tissues are inflamed, therefore, reducing
the pressure on the edematous and
injured tissues distal to the condyle.
The effectiveness of the orthosis can be
enhanced with concomitant use of
pharmaceuticals such as NSAIDs.
The inherent design of the
appliance should provide:
Redistribution of occlusal forces.
Relaxation of the elevator
Stabilization of the TMJ.
Protection of the dentition.
Decrease in symptoms.
Reduction of bruxism.
The design of of stabilization orthosisThe design of of stabilization orthosis
A full arch.
Flat plane orthosis.
Can be maxillary or mandibular.
Undulation dictated by the occlusal
Flat but if indentations exist it should in
centric bearing cusp and incisal edge of
Maxillary appliance has the
advantages to achieve occlusal
contact with the opposing teeth
regardless of the maxillo-
mandibular relationship which is
not possible with the lower
appliance, despite that the
mandibular appliance is more
esthetic and does not affect the
Design of the maxillary appliance;
It should be horseshoe shape.
Should have clasp on both sides.
Acrylic should overlap buccal and labial of the
teeth to prevent any movement.
Flat occlusal surface with even contact in
centric-bearing cusp of the posterior teeth as
well as the incisal edge of the lower anterior
Anterior acrylic ramp is to provide disclusion of
posterior teeth in the lateral movements.
In an effort to minimize the adjustment
time, an interocclusal record at the
desired vertical dimension should be
done and which will be used for
mounting the opposing cast, so that the
appliance will be fabricated at a jaw
relationship within the physiologic
parameters of the patient.
The clearance between the tow jawsclearance between the tow jaws
should never exceed the freewayshould never exceed the freeway
spacespace, if not the muscle tone, which is
the passive resistance to stretch, will be
affected concomitant with fatigue
Also adjustment is needed to
perform an even contact during
habitual closure as well as inhabitual closure as well as in
occlusion in CRocclusion in CR so the patient
can use it during sleeping time and
It is important to remind that the
inerocclusal record should be
performed in reclined positionreclined position
( occlusion in CR ).
The healing phase that follows the
appliance therapy shows:
Reduction of pain.
Reduction of edema and inflamed
Reduction of muscle activity.
Clinical examination suggests that this
improvement is on a psychology basis.
However, these results are on the basis
of the even contact in CR occlusion as in
Stabilization orthosis is generally worn
during increase of muscle activityduring increase of muscle activity,
normally at nightnormally at night, but it could be use
during waking hours.
Duration of wearing the orthosis can be
reduced as signs and symptomsreduced as signs and symptoms
If the disorder affect just the muscles,
using the orthosis during sleeping is to
If the TMJ is affected (intracapsular
disorder) full time wearing the orthosis
during the initial stage may be indicated.
When symptoms are overWhen symptoms are over, using the
orthosis is not necessary anymore, but
intermittent wearing may be necessary
during stressful life events.
At this stage, the muscles are well
relaxed, so guiding the mandible in
occlusion in different positions will be
helpful in finding out the important
interferences in a clear way.
Adjustment of these interferences is
helpful in the treatment of the signs and
the symptoms of bruxism.
One month useOne month use is enough to expectis enough to expect
positive patient responsepositive patient response.
In case where symptoms affect the
myofacial and temporal muscles, the
anterior flat biteplane is indicated, it is
fabricated by hard acrylic and come in
contact with just the lower anterior teeth.
It affects brux. and parafunctional
It is effective when the chief complain is
limited to muscle pain. Its use limited on
sleeping hours to avoid posterior teeth
Concerning the appliance material; one study
indicated that hard interocclusal orthosis is likely to
be more successful than soft orthosis in reducing
nocturnal muscle activity as well as myofacial pain
Also soft material is more difficult to adjust, and
contribute to inadvertent tooth movement and
However, soft orthosis has certain indications as
transitional one for emergency cases and as athletic
Adjunctive physical therapyAdjunctive physical therapy; it is
useful in managing the pain of
masticatory muscles related to bruxism,
Stretch and spray with vapocoolant.
Masticatory muscle exercises.
Patient awareness of parafunctional
Trans cutaneous electric stimulation.
For both diagnostic and short
management approach, using a
pharmaceutical anti anxiety agent
is to be considered, diazepam
demonstrated good resultsdemonstrated good results.
agent would suppress the REMREM
stage of sleepstage of sleep which has an
association with bruxism.