GOOD MORNING

GOOD MORNING

PRESENTED BY:DR.MURALI P.SDEPARTMENT OF ORTHODONTICS AND DENTOFACIAL ORTHOPAEDICS

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MUSCLES OF MASTICATION

CONTENT

Introduction Development of muscle of masticationAnatomy of Muscles of masticationPhysiology of muscles of masticationCharacteristic of muscles of jaw Palpation of muscles of mastication Significance in relation to orthodontics Masticatory muscle disorder pathological diseases of muscles of mastiction Conclusion

INTRODUCTIONOrthodontist aim is to achieve FUNCTIONAL EFFICIENCY STRUCTURAL BALANCE ESTHETIC HARMONYto achieve this balance not only our concepts regarding occlusion has to be clear,,,,,,,,,,,It is also important that we realize and study the action of various muscle of expression, mastication, deglutition, speech and breathing.

INTRODUCTIONOrthodontist aim is to achieve FUNCTIONAL EFFICIENCY STRUCTURAL BALANCE ESTHETIC HARMONYto achieve this balance not only our concepts regarding occlusion has to be clear,,,,,,,,,,,It is also important that we realize and study the action of various muscle of expression, mastication, deglutition, speech and breathing

DEVELOPMENTMuscles of mastication develops from the mesoderm of the first brachial arch that is also called mandibular arch.Muscles begins differentiation in seventh week of intra uterine life. Although the muscle of mastication develop at first in close relationship to meckels cartilage and the cranial base cartilages, they are independent and only later attach to the bony skeleton.

Temporalis :Begins lateral development in the 8th week , occupying the space anterior to the otic capsule . As the temporal bone begins ossify in the 13th week, the muscle attaches to it. Masseter: Begins attachment to the zygomatic arch as it undergoes lateral growth, providing space for muscle development.

Pterygoid muscle:Differentiate in the 7th week. It is related to the cartilage of the cranial base and the condyle initially.Later as the bony skull appears and increases in width and length, the muscle expands rapidly.

ANATOMYORIGININSERTION BLOOD AND NERVE SUPPLYACTION

MASETTERThis is a quadrilateral muscle. which covers the lateral surface of the ramus of mandible Its fibres has 3 layers Superficial Middle Deep layers

Origin:superficial layer Originates from anterior 2/3rd of the lower border of zygomatic arch and from zygomatic process of the maxillaMiddle layer --From anterior 2/3rd of deep surface and posterior 1/3rd of lower border of zygomatic archDeep layer -from the deep surface of the zygomatic arch

INSERTION:Fibres of the superficial layer pass downwards and backwards to insert into the angle and lateral surface of the mandibular ramus.Fibres of the middle layer insert into the central part of the mandiblular ramusFibres of the deep layer insert into upper part of the mandibular ramus and into it's coronoid process.

RELATIONS:Superficial relations:Skin, Platysma Risorious, Zygomaticus Major and Parotid Gland. Muscle is crossed by the parotid duct, branches of facial nerve and transverse facial vessels.Deep relations:Temporalis and mandibular ramus.A mass of fat separates it in front of the buccinator and the buccal nerve.Masseteric nerve and artery reach the deep surface of the muscle.

Nerve supply:Supplied by masseteric nerve a branch of anterior division of mandibular nerve

Blood supply:Supplied by masseteric artery branch of maxillary artery and venous supply through masseteric vein

Action:Elevation(bilateral):masseter elevates the mandible to occlude the teeth in mastication.Ipsilateral excursion(unilateral): as the origin of the masseter muscle is slightly lateral to its insertion , a single masseter muscle can move the mandible to the same side.Retrusion: (bilateral): when the mandible is in a protruded position the deep fibers are in a position to retrude the mandible.

TEMPORALIS MUSCLE

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Large, fan shaped muscle.The muscle is covered by a strong membranous sheet of fascia, which attaches superiorly to superior temporal line.

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Origin:

originates from the temporal fossa and lateral surface of skull.

Insertion: It's fibers converge and descend into a tendon which passes through the gap between zygomatic arch and side of skull and attaches to the medial surface, apex, anterior and posterior borders of the coronoid process and the anterior border of ramus of the mandible.

It can be divided into 3 distinct areas according to fiber direction and function.The Anterior fibers are directed almost vertically- elevation of mandibleThe middle fibers run obliquely forward as they pass downward -elevate and retrude the mandible.The posterior fibers are aligned almost horizontally - retrusion of mandible.

Relations:

Superficial :Skin, temporal fascia, superficial temporal vessels, auriculotemporal nerve, zygomatico temporal nerve zygomatic arch and Masseter muscle.Deep Relation : Temporal fossa lateral pterygoid, superficial head of the medial pterygoid and maxillary artery.Nerve Supply : Deep temporal branches of the anterior trunk of the mandibular nerve.

ACTIONS :

i.Elevation(bilateral):Temporalis elevates the mandible to close mouth and approximate the teeth, this movement requires the both the upward pull of the anterior fibres and backward pull of the posterior fibres.

Retrusion(bilateral): the posterior fibers of temporalis lie in an almost horizontal plane and therefore are in a good position to pull the protruded mandible to a centric position.

Ipsilateral excursion: The insertion of temporalis is medial to the origins and therefore temporalis muscle is capable of pulling the mandible to the same side.

MEDIAL PTERIGOIDDeep head: Origin: Medial surface of the Lateral plate of Pterygoid process and Pyramidal process of Palatine bone. Insertion : Medial surface of the ramus of Mandible near the angle.

Superficial head:Orgin:Tuberosity of the maxilla and pyramidal process of palatine boneInsertion : it joins deep head to insert on the Mandible

Nerve supply : Nerve to Medial Pterygoid from the Mandibular Nerve.Blood Supply : Pterygoid branches from Maxillary artery

Action : Elevation (bilateral) : the medial pterygoid acting along with the masseter muscle are powerful elevators of the mandible. Protrusion( bilateral): the insertion of the muscle is posterior to its origin and therefore it helps in protrusion of mandible.Contralateral excursion: the medial and lateral pterygoid muscle of two sides contract alternately to produce Side-to-Side movement of Mandible.

Lateral pterygoidUpper head:Origin : It arises from the infratemporal surface and crest of the grater wing of the sphenoid bone.Insertion: The upper head passes posteriorly and lateraly to insert into the articular capsule and the articular disc.

Lower head:Origin :It arises from the lateral pterygoid plate of sphenoid bone.Insertion : The inferior head passes back ward , upward and slight laterally to insert into the pterygoid fossa of condylar neck.

Nerve supply : Nerve to Lateral Pterygoid from the Mandibular Nerve.

Blood Supply : Pterygoid vessels from Maxillary artery

Action :Action of inferior head:Depression(bilateral): depresses the mandible along with suprahyoid and infrahyoid muscles to open the mouthProtrusion(bilateral): the lateral pterygoid acting together are the prime protractors of the mandible.Contralateral excursion(unilateral): the medial and lateral pterygoid muscle of the two sides contact alternately to produce side to side movement of the mandible(as in chewing).

Action of superior head:They are active during the power stroke.Power stroke refers to movement that involves closure of the mandible against resistent such as in chewing or clenching the teeth together.

RELATIONS:Superficial :Ramus of mandible, maxillary artery and the tendon of temporalis Deep :Upper part of the medial pterygoid, sphenomandibular ligament, middle meningeal artery and mandibular nerve.Upper border :It is related to the temporal and Masseteric branch of mandibular nerve.Lower border : It is related to the lingual and inferior alveolar nerve.The buccal nerve and maxillary artery pass between two heads.

Accessory muscles of masticationAccessory muscles are :Digastric(anterior and posterior)StylohyoidMylohyoidBuccinator

DigastricPosterior belly:Ori : Mastoid process of Temporal boneAnterior belly:Ori : Body of Mandible

Ins : Intermediate Tendon is held to hyoid bone by fascial sling

Nerve supply : Facial Nerve (post belly) nerve to mylohyoid (ant belly)Action : Depresses Mandible or elevates Hyoid bone

Stylohyoid:Ori : Styloid processIns : Body of Hyoid boneNerve supply : Facial nerveAction : Elevates hyoid bone

Mylohyoid:Ori : Myloid line of body of MandibleIns : Body of Hyoid bone and fibrous rapheNerve supply : Inferior Alveolar nerveAction : Elevates floor of mouth and hyoid bone or depresses mandible

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Ori : Posterior part of Maxilla , Mandible and Pterygomandibular rapheIns : Lip, blending with fibres of Orbicularis Oris

Is thin quadrilateral muscle, occupying the interval between the maxilla and the mandible

Buccinator

Nerve supply: - supplied by the lower buccal branch of the facial nerveAction: - It compresses the cheek against the teeth so helps in mastication as the food is passed between them.It helps in blowing, hence the name buccinator.

Role of masticatory muscle in mandibular movement

Mandibular movements during normal function and during Para function involve complex neuromuscular patterns originating in the brain stem and modified by influences from higher centers namely cerebral cortex basal ganglia peripheral influences (e.g. peridontium, muscles )

Mandibular Closing :

Mandible is elevated slowly without occlusal contact, is brought about by the contraction of the masseter and medial pterygoid muscle.

Mandible is elevated against resistance, it is brought about by the contraction of the temporalis, masseter and medial pterygoid muscles.

MANDIBULAR OPENING :

During opening movements, the lateral pterygoid muscles show initial and sustained activityIn forced depression the digastic muscle is activated along with the lateral pterygoid muscle.

PROTUSION :

The lateral and medial pterygoid muscles contract together, in conjunction with controlled stabilizing relaxation of opening muscle

RETRUSION : Voluntary mandibular retrusion with occlusion is brought about by contraction of the posterior fibers of the Temporalis muscle and by the suprahyoid and infrahyoid muscles. Retraction of the mandible from protrusion and without occlusal contact is effected by the contraction of the posterior and middle fibers of the Temporalis muscles.

PHYSIOLOGY OF MUSCLES OF MASTICATIONIt is skeletal muscle.

Types of muscle fiber: Slow muscles fibers (type I)

Fast muscles fibers (type II)

Lateral movement:Lateral movement of the mandible to the right side without occlusal contact is achieved by ipsilateral contraction of primarily the posterior fibers of the Temporalis muscle.Movement to the left side without occlusal contact is brought about by the contralateral contraction of the medial pterygoid and masseter muscles. Movement to the right side with occlusal contact is achieved by ipsilateral contraction of the Temporalis muscle. Movement to the left with occlusal contact is brought about by contralateral contraction of the medial pterygoid and masseter muscles.

45 Slow muscle fibers:-[Tonic muscles]: These are the muscles which are redder in colour because of some pigment protein myoglobin.These are also called as the type I fibers.E.g. Temporalis, the masseter, the anterior medial pterygoid and the lateral pterygoid are 75 % composed of type I fibers. [Eriksson]

Fast muscles fibers: They are paler in colourThey are also considered as the type II muscle fibersAcc. To burke et .al 1973 type can be subdivided into fibers which fatigue easily [type IIB] and the other one which are resistant to fatigue [type II A]. Type IIA is found in 30 % only in digastric muscle. Type IIB is found in 45 % in the superior temporalis, posterior medial pterygoid, and anterior digastric muscle. [Acc to Eriksson]

47Reflexes of the muscles:-Reflex: A reflex action is the response resulting from a stimulus that passes as an impulse along an afferent neuron to the posterior nerve root or its cranial equivalent, where it is then transmitted to an efferent neuron leading back to skeletal muscle. Most imporatantMyotactic reflex Nociceptive (flexor) reflex.

Myotactic (stretch) reflex:They are monosynaptic jaw reflex.When skeletal muscle is quickly stretched this protective reflex is elicited and bring about a contraction of the muscles.myotactic reflex is activated by sudden application of downward force to the chin

Results in sudden stretching of the muscle spindle increases afferent out put from the spindle

These afferent impulse pass into the brain stem to the trigeminal motor nucleus (where afferent cell body are present) by way of trigeminal mesencephalic nucleus.

In trigeminal motor nucleus the afferent fibers synapse with alfa efferent motor neurons that lead directly back to the extrafusal fibers of the elevator muscle.

The reflex information sent to the extrafusal fiber is to contract.

Prevent further stretching and often causes an elevation of the mandible into occlusion

50Myotactic reflex

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This reflex is used in myofunctional appliances like activator.The appliance is trimmed loosely and the patient is conditioned to bite into the appliance to keep it in position.When the mandible moves mesially to engage the appliance, the elevator muscles are stretched.Thus the myotatic reflex is activated, the muscles contract and the forces elicited help in causing skeletal and dento-alveolar changes.

52Nociceptive (flexor) reflex:-It is a polysynaptic reflex to noxious stimuli and is thus considered protective reflexThe afferent neuron stimulates one or more interneuron's in the CNS which in turn stimulate the efferent fibers.The nociceptive reflex is activated by unexpectedly biting on a hard object.

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The Afferent fibers stimulateinhibitory interneuron's whichhave their effect on the jaw elevating muscles and cause them to relax.

The afferent fibers stimulate excitatory interneuron that innervate the jaw depressing muscle to cause contraction.

Characteristics of the jaw muscles:-The mandible being maintained against the gravity by the stretch reflex of the elevators.EMG studies have shown of [postural position] that the inframandibular groups of muscles are more active than the levator.The head posture also affects the posture of the mandible for e.g. when there is extension of the head there is increase in the freeway space and when there is flexion there is decrease in the freeway space.

Changes in the head posture also results changes in the anteroposterior positioning of the posture of the mandible.One of the most important factors is the posture of the mandible affecting the development of the jaws.E.g. during the mouth breathing there is effect on the growth of both maxilla as well as the mandible due to alteration in position of the mandible, hyoid and the tongue.

56Palpation of muscles:-The muscles of mastication are palpated for tenderness or pain during the screening examination. It is accomplished mainly by the palmar surface of the middle finger, with the index finger and the forefinger testing the adjacent areas.Soft but firm pressure is applied to the designated muscles, the fingers compresses the adjacent tissues in a small circular motion.

The temporalis: - It has three functional areas and each is independently palpated.Anterior region: - Palpated above the zygomatic arch and anterior to the TMJ.

Middle region: - Directly above TMJ and superior to the zygomatic arch

Posterior region: - Palpated above and behind the ear. Otherwise, the patient is asked to clench the teeth so that the temporalis contracts and this is felt with hands.

The masseter muscles :Are palpated bilaterally at their superior and inferior attachments.The fingers are placed on the zygomatic arches and then dropped down slightly just anterior to the tmj for palpating superior part.Secondly, the fingers are placed on the inferior border of the rami to palpate inferior attachment.

Medial pterygoid: - Finger tips are placed on the inferior border of the mandible at the angles and are rolled medially and superiorly. Ask the patient to clench the teeth if it is difficult to locate the muscle.

The lateral pterygoid :Palpation is difficult.It is accomplished by placing the forefinger or little finger behind the maxillary tuberosity, right above the occlusal plane, with the palmar surface of the finger directed medially toward the pterygoid hamulus.If there is tenderness in the superior head of the lateral pterygoid muscle than it indicates abnormal functional loading of the joint.

The finding are classified into four categories.- 1. Zero: - no tenderness or pain is reported by the patient, 2. One: - patients response is recorded. Here the palpations cause discomfort. 3. Two:-there is definite discomfort or pain. 4. Three: - patient shows evasive action or verbally expresses desire not to palpate.

Functional manipulationThree muscles that are basic to jaw movements but impossible or nearly impossible to palpate are (1) the inferior lateral pterygoid, (2) superior lateral pterygoid, (3) medial pterygoid..

Functional manipulation of the inferior lateral pterygoid: Contraction.: When the inferior lateral pterygoid contracts, the mandible is protruded, the mouth is opened, or both. Functional manipulation is best accomplished by having the patient make a protrusive movement, because this muscle is the primary protruding muscle

Therefore the most effective manipulation is to have the patient protrude against resistance provided by the examiner If the inferior lateral pterygoid is the source of pain, this activity will increase the pain

Stretching:The inferior lateral pterygoid stretches when the teeth are in maximum intercuspation. Therefore if it is the source of pain when the teeth are clenched, the pain will increase. When a tongue blade is placed between the posterior teeth, the intercuspal position (ICP) cannot be reached; therefore the inferior lateral pterygoid does not stretch. Consequently, biting on a separator does not increase the pain but may even decrease or eliminate it.

Contraction.: The superior lateral pterygoid contracts with the elevatormuscles i.e.,temporalis, masseter,medialpterygoid), especially during a power stroke (i.e., clenching). Therefore if it is the source of pain, clenching will increase the pain. If a tongue blade is placed between the posterior teeth bilaterally and the patient clenches on the separator, pain again increases with contraction of the superior lateral pterygoid.

These observations are exactly the same as for the elevator muscles. Stretching is needed to enable superior lateral pterygoid pain to be distinguished from elevator pain.Functional manipulation of the superior lateral pterygoid

Stretching:-As with the inferior lateral pterygoid, stretching of the superior lateral pterygoid occurs at maximum intercuspation. Therefore stretching and contracting of this muscle occur during the same activity: clenching. If the superior lateral pterygoid is the source of pain, clenching will increase it. Superior lateral pterygoid pain can be differentiated from elevator pain by having the patient open widely. This will stretch the elevator muscles but not the superior lateral pterygoid. If opening elicits no pain, then the pain of clenching is from the superior lateral pterygoid.

Functional manipulation of the medial pterygoid Contraction: The medial pterygoid is an elevator muscle and therefore contracts as the teeth are coming together. If it is the source of pain, clenching the teeth together will increase the pain. When a tongue blade is placed between the posterior teeth and the patient clenches against it, the pain is still increased because the elevators are still contractiStretching.: The medial pterygoid also stretches when the mouth is opened widely. Therefore if it is the source of pain, opening the mouth wide will increase pain.

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Role of masticatory muscle in orthodontics

70Muscle as the etiology of malocclusion Muscle dysfunction:- The facial muscles can affect the growth of the jaws in two ways:-The formation of the bone at the point of muscle attachment depends on the activity of the muscles The musculature is important part of the total soft tissue matrix, whose growth normally carries the jaws downward and forward.

71Facial asymmetry in a eleven yr old boy whose masseter muscle was missing on left side. So the muscle is an important part of total soft tissue matrix,in its absence growth of the mandible is affected.

72If there is decrease in tonic muscles activity that occurs in muscular dystrophy, this allows the mandible to drop downward away from the rest of the facial skeleton.

This results in increase of the anterior facial height, distortion of facial proportions , mandibular form, excessive eruption of the posterior teeth, narrowing of the maxillary arch and anterior open bite. Ex: in cerebral palsy

73Patterns of muscular activity in patients with class III malocclusionsDominant bone dysplasia, with adaptive muscle function

Strong heredity pattern

Here the anterior and the posterior temporal muscle are found to be more active than that of masseter muscle in the interocclusal position.

The mandibular muscles and their importance in orthodontics: A contemporary review(AJO 2005,128:774-80)

THE RELATIONSHIP BETWEEN CRANIOFACIAL MORPHOLOGY AND THE MANDIBULAR MUSCLES :Bite-force and facial morhology:In dolichofacial subjects, significantly smaller maximum molar bite forces have been found during maximum effort than in mesofacial and brachyfacial subjects.

This implies a correlation between bite force and facial morphology, and these findings have been used to support the theory that the form of the face partly depends on the strength of the mandibular muscles. Ingervall and Helkimo found that adults with weak muscles have a greater variation in facial morphology than those with strong muscles,

The efficiency with which a muscle generates a force at a particular point is defined as the ratio of the moment arm of the muscle to the moment arm of the load. Throckmorton et al attempted to explain that the significantly smaller bite force of dolichofacial subjects is due to the reduced mechanical advantage of the mandibular muscles.

. According to Kiliaridis, strong muscles produce faces with similar morphologic features, whereas weak muscles cannot influence the morphology to such an extent.Those with weak mandibular muscles can belong to either the mesofacial or the dolichofacial group.

Cross-sectional area of the mandibular muscles and facial morphology:Many authors have described the relationship between the cross-sectional area of the mandibular muscles and facial morphology.A common finding has been that the masseter and medial pterygoid muscles have large cross-sections in people with short anterior face heights and small gonial angles.

Also the maximum force that can be produced by a muscle is dependent on its cross-sectional area. Hannam and Wood found a statistically significant correlation between masseter and medial pterygoid cross-sectional areas and molar bite force

Position, orientation and mechanical advantage of the mandibular muscles:According to Takada et al, a short posterior face height with steep mandibular plane and large gonial angles is often associated with an anteriorly inclined superficial masseter to the occlusal plane and a superior positioning of its insertion on the mandible.

Haskell et al reported that the superficial masseter was angled considerably more anteriorly with a much more acute angle to the occlusal plane in a dolichofacial pt when compared with a brachyfacial pt whether masseter angulation is constant relative to the occlusal plane is controversial.Although Proctor and DeVincenzo noted a constant angular relationship (about 69) between the superficial masseters and the occlusal planes.

Cause and effect relationship between muscle function and craniofacial morphology:

In animal studies, it has been shown that interference with the development of the jaw and facial muscles can lead to major changes in the shapes of jaw bones. It has also been shown that human subjects with strong bite forces tend to have brachyfacial patterns, in contrast to those with weak bite forces, who tend to have dolichofacial patterns. This difference in bite force has led to much speculation about the etiology of vertical facial patterns.

According to Proffit and Fields, it is possible that the lower bite force in dolichofacial people might allow greater eruption of the posterior teeth than might otherwise occur, and so are directly related to the excessive tooth eruption and backward rotation of the mandible.Ingervall and Helkimo suggested that the interindividual form of the face is smaller in persons with strong muscles than in those with weak muscles. This would support the hypothesis that the muscles do actually contribute to the final shape of the face.

The ingervall and bitsanis, who showed that training the jaw muscles in dolichofacial children strengthened these muscles and induced a favorable anterior mandibular growth rotation.

CONSIDERATION OF THE MANDIBULAR MUSCLES AND VERTICAL FACIAL PATTERN DURING ORTHODONTIC TREATMENT:

Forward-rotating brach facial subjects tend to have deep overbites, whereas backward-rotating dolichofacial subjects tend to have open bit.In general, most brachyfacial patients require bite-opening mechanics during orthodontic treatment, in what is often a powerful muscular environment. dolichofacial patients usually require some limiting of vertical development during treatment to avoid extrusion of the posterior teeth.

Brachyfacial subject , with deep overbite tends to resist extrusive forces during orthodontic treatment. If molar extrusion does occur during treatment in brachyfacial patients, there is likely to be a strong tendency toward reintrusion through the influence of the strong muscles during swallowing and chewing. Thus, it might be difficult to cause permanent extrusion of the molars and backward rotation of the mandible in such patients, even though this is a main aim of treatment.

In dolichofacial pt ,inter maxillary elastics or headgears (extrusive force) should be avoided during treatment, to prevent any undesirable backward rotation of the mandible.

In such patients, it is crucial to really control the vertical dimension if stability, facial balance, and harmony are the ultimate goals of treatment.

88Post surgical stability and muscles

Three principles that influence post surgical stability 1.Stability is greatest when soft tissues are relaxed during surgery & least when they are streched .

Maxilla up---relaxes the tissue Moving mandible forward ----streches Rotating up at gonial angle and down at chin -----Strech

892.Neuro muscular adaptation is essential for stabilityMost procedures good nm adaptationAny procedure streching pterygomandibular sling nm adaptation doesnot occurSyndromic pts cannot adapt to changes.

3.Nm adaptation affects muscular length, not muscular orientationIf orientation of a muscle group such as the mandibular elevators is changed adaptation cannot be expectedSuccessful mandibular advancement requires keeping ramus in upright position,rather than letting it inclined forward as mandibular body is brought forward

Masticatory muscle disorderThere are five types of masticatory muscle disorder.1.PROTECTIVE CO-CONTRACTION (MUSCLE SPLINTING)2. LOCAL MUSCLE SORENESS (NONINFLAMMATORY MYALGIA)3. MYOSPASMS (TONIC CONTRACTION MYALGIA)4.MYOFASCIAL PAIN (TRIGGER POINT MYALGIA) 5.CENTRALLY MEDIATED MYALGIA (CHRONIC MYOSITIS)

PROTECTIVE CO-CONTRACTION (MUSCLE SPLINTING): Protective co-contraction is the initial response of a muscle to altered sensory or proprioceptive input or injury (or threat of injury). This response has been called protective muscle splinting or coactivation. CAUSEAltered sensory or proprioceptive input The presence of constant deep pain inputIncreased emotional stress

CLINICAL CHARACTERISTICS Structural dysfunction: decreased range of movement, but the patient can achieve a relatively normal range when requested to do soMinimal pain at restIncreased pain with functionA feeling of muscle weakness

DEFINITIVE TREATMENT;Treatment should be directed toward the reason for the co- contraction. When co- contraction results from trauma, definitive treatment is not indicated because the cause is no longer present.When co-contraction results from the introduction of a poorly fitting restoration, definitive treatment consists of altering the restoration to harmonize with the existing occlusion. Altering the occlusal condition to eliminate co-contraction is directed only at the offending restoration and not the entire dentition. Once the offending restoration has been eliminated, the occlusal condition is returned to its preexisting state, which resolves the symptoms.

SUPPORTIVE THERAPY:It begins with instructing the patient to restrict use of the mandible to within painless limits. A soft diet may be recommended until the pain subsides. Short-term pain medication (nonsteroidal anti inflammatory drugs [NSAIDs]) may be indicated.

LOCAL MUSCLE SORENESS (NON INFLAMMATORY MYALGIA) :Local muscle soreness is a primary, non inflammatory, myogenous pain disorder. Local muscle soreness represents a change in the local environment of the muscle tissuesCAUSE:Protracted protective co-contraction secondary to a recent alteration in local structures or a continued source of constant deep painLocal tissue trauma or unaccustomed use of the muscleIncreased levels of emotional stress

CLINICAL CHARACTERISTICSStructural dysfunction: marked decrease in the velocity and range of mandibular movement (full range of movement cannot be achieved by patient)Minimum pain at restPain increased with functionActual muscle weakness presentLocal tenderness when the involved muscles are palpated

DEFINITIVE TREATMENTEliminate any ongoing altered sensory or proprioceptive input.Eliminate any ongoing source of deep pain' input (whether dental or other).Provide patient education and information on self-management (PSR).

SUPPORTIVE THERAPYSupportive therapy for local muscle soreness is directed toward reducing pain and restoring normal muscle function. However, if pain continues, it can usually be controlled with a mild analgesic such as aspirin, acetaminophen, or an NSAID (e.g., ibupro-fen). Manual physical therapy techniques such as passive muscle stretching and gentle massage may also be helpful. Relaxation therapy may also be helpful if increased emotional stress is suspected.Local muscle soreness should respond to therapy in 1 to 3 weeks.

MYOSPASMS (TONIC CONTRACTION MYALGIA)Myospasm is an involuntary, CNS-induced, tonic muscle contraction often associated with local metabolic conditions within the muscle tissues. CAUSE:Continued deep pain inputLocal metabolic factors within the muscle tissues associated with fatigue or overuseIdiopathic myospasm.

CLINICAL CHARACTERISTICSStructural dysfunction: marked restriction in range of mandibular movement according to the muscles involved; acute malocclusion commonPain at restPain increased with functionAffected muscle is firm and painful when palpated.Generalized feeling of significant muscle tightness

DEFINITIVE TREATMENT:Myospasms are best treated by reducing the pain and then passively lengthening or stretching the involved muscle. Reduction of the pain can be achieved by manual massage, vapor-coolant spray, ice, or even an injection of local anesthetic into the muscle in spasm. When obvious causes are present (i.e., deep pain input), attempts should be directed toward elimination of these factors so as to lessen the likelihood of recurrent myospasms. SUPPORTIVE THERAPY:Often physical therapy techniques are the key to managing myospasms. Soft tissue mobilization such as deep massage and passive stretching .

MYOFASCIAL PAIN (TRIGGER POINT MYALGIA) Myofascial pain is a regional myogenous pain condition characterized by local areas of firm, hypersensitive bands of muscle tissue known as trigger points .This condition is also called myofascial trigger point pain. CAUSE:Continued source of deep pain inputIncreased levels of emotional stressPresence of sleep disturbancesLocal factors such as habits, posture, muscle strains, or even chilling

CLINICAL CHARACTERISTICSStructural dysfunction:The heterotopic pain is felt even at rest.Pain may increase with function.When provoked,the trigger points increase the heterotopic pain.DEFINITIVE TREATMENTEliminate any source of ongoing deep pain input in an appropriate manner according to the cause.Reduce the local and systemic factors that contribute to myofascial pain. If a sleep disorder is suspected, low dosages of a tricyclic antidepressant, such as 10 to 20 mg of amitriptyline before bedtime, can be helpful

One of the most important considerations in the management of myofascial pain is the treatment and elimination of the trigger points. Its done bySprai/ and StretchPressure and MassageUltrasound and Electrogalvanic Stimulationinjection and StretchSUPPORTIVE THERAPYVarious physical therapy modalities and manual techniques are used to treat myofascial pain.

CENTRALLY MEDIATED MYALGIA (CHRONIC MYOSITIS):Centrally mediated myalgia is a chronic, continuous muscle pain disorder originating predominantly from CNS effects that are felt peripherally in the muscle tissues. This disorder clinically presents with symptoms similar to an inflammatory condition of the muscle tissue and therefore is sometimes referred to as myositis. Clinical charecteristic:structural dysfunction.Significant pain at restPain increased with functionGeneralized feeling of muscle tightnessSignificant pain to muscle palpationAs chronic centrally mediated myalgia becomes protracted, it may induce muscle atrophy and/or myostatic or myofibrotic contracture.

DEFINITIVE TREATMENTchronic centrally mediated myalgia ,the outcome of therapy will not be as immediate as with treating local muscle soreness NSAID such as ibuprofen is a good choice and should be given to relive pain.

SUPPORTIVE THERAPYEarly in the treatment of chronic centrally mediated myalgia, physical therapy modalities should be used cautiously because any manipulation can increase the pain. Sometimes moist heat can be helpful.

Congenital and developmental muscle disdorder: Common congenial muscle and developmental muscle dissoder can be divided into 3 categories1. Hypertrophy2.Hypotrophy(lack of development)3.Neoplasia

Masseter muscle hypertrophy:There is over development of the muscle.Hypertrophic changes may be secondary to increased use such as bruxism.They rarely show any symptomsHypertrophy may observer as a large masseter muscle.Treatment: When hypertrophy is present secondary to bruxism, a muscle relaxation appliance is given.

Pathological diseases of muscles of mastication

MYASTHENIA GRAVISIt is a chronic disease with progressive weakness of skeletal musclesCaused by destruction of acetyl choline receptors at neuromuscular junctionThis is autoimmune conditionMuscles of mastication are involved before any other muscle groupDifficulty in mastication ,deglutition and dropping of jaw is seen

TreatmentDrug of choice is physostigmine and anticholinisterase administered intramuscularly(im) ,which improves the strength of muscles in minutes

TRISMUSThere is stiffness of muscles of masticationEtiologyLocal infection pericoronitis,dentoalveolar abscessDirect trauma to muscles of masticationCns tetanus, rabiesLocal infectionPressure is on med.Pterygoid and masseter leading to irritation and consequent spasm TetanyInfection is caused by clostridium tetanus which releases powerful exotoxin thus destroying the spinal inhibition causing uncontrolled muscle spasmIn muscles of mastication it causes lock jaw

MYOFACIAL PAIN DYSFUNCTION SYNDROME:Spasm of muscles of mastication occures due to overuse, trauma ,stress and strain plays an important role

Signs and symtomsUnilateral dull pain in earTenderness of one or more muscles of mastication on palpationLimitation or deviation of mandibular opening Clicking or popping at tmj

TreatmentLocal anaesthetic inj at trigger points thus breaking the spasm Soft diet is recommendedAspirin or nsaid prescribedTens (transcutaneous electric nerve stimulation)

Conclusion: It is crucial responsibility of orthodontist to recognize each persons muscular environment and be aware of the problems related with excessive or deficient use of muscle and their bearing to the dentition. Final result can be stable until environmental harmony can be achieved.

REFERENCES Grays anatomy willams,bannister,colin-38th edition Cunninnghams manual of practical anatomy head neck & brain Inderbig singhs text book of anatomy head & neck vol 3 Text book of oral pathology shafers,hine,--4th edition Oral medicine diagnosis and treatment burket -10th editin Proffit contamporary orthodontics Graber and neumann removable orthodontic appliance Graber --orthodontics 3rd edition

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