Muscles of mastication ppt

GOOD MORNING

LAB

WORK

ANISH YOGESH AMIN

INTRODUCTION TYPES OF MUSCLE FIBERS

FUNCTIONS OF MUSCLE

FIBERS

REFLEX MECHANISMS

PROSTHODONTIC IMPLICATIONS

MASTICATORY MUSCLES

CONCLUSIONDISORDERS OF

MASTICATORY MUSCLES

REFERENCES

MUSCLE is defined as a

tissue composed of

contractile cells or fibers

that effect movement of an

organ or part of the body.

TYPES OF MUSCLES

Glossary Of Prosthodontic Terms 8

ISOTONIC CONTRACTION

ISOMETRIC CONTRACTION

CONTROLLED RELAXATION

Stimulation of large no of motor units Overall shortening of muscle under constant load Eg: Occurs in Masseter muscle(during elevation of mandible)

forcing teeth through bolus of food

ISOTONIC CONTRACTION

Proper no. of motor units are stimulated Muscle does not shorten Eg: Occurs in Masseter muscle, when an object is

held between the teeth

ISOMETRIC CONTRACTION

Stimulation of motor units discontinued Muscle returns to its normal length Eg: Occurs in Masseter muscle when the mouth opens

to accept a new bolus of food

CONTROLLED RELAXATION

“MANDIBULAR

ARCH”

The basic muscles of mastication develop from the mesenchyme of first branchial arch

MASTICATION

Mastication (1649): Process of chewing food for swallowing and digestion

GLOSSARY OF PROSTHODONTIC TERMS 8

Four major muscles Masseter Temporalis Medial pterygoid(internal) Lateral pterygoid (external)

• DIGASTRIC

• MYLOHYOID

• GENIOHYOID

• INFRAHYOID

ORIGIN INSERTIONSuperficial layer

Anterior 2/3rd of lower border of zygomatic arch

Lower part of lateral surface of ramus

Middle layer Posterior 1/3rd of lower border of zygomatic arch

Middle part of ramus

Deep layer Deep surface of zygomatic arch

Upper part of ramus & coronoid process

NERVE SUPPLY:MASSETERIC BRANCH OF MANDIBULAR NERVE

•May become overdeveloped due to bruxism•Parotid gland lies on the top of this muscle•Masseter hypertrophy may shut off flow from parotid

Elevates mandible Brings molars together for crushing

and grinding-”chewer “ muscle Forms half of mandibular sling (medial pterygoid forms the other half)

ON DENTURE BORDER:

An active masseter muscle will create concavity in the outline of the distobuccal border

A less active masseter may result in convex border

In this area the buccal flange must converge medially to avoid displacement due to contraction of the masseter muscle, because the muscle fibers in that area are vertical and oblique

Instruct the patient to open mouth wide and then close against the resting force of your finger

Opening wide activates the muscles of pterygomandibular raphe by stretching, which thereby defines the most distal extension

Instructing the patient to close against the finger on tray handle causes masseter muscle to contract & push against the medially situated buccinator muscle

MASSTERIC NOTCH REGION

•\

NERVE SUPPLY: 2 deep temporal branches of mandibular nerve

ORIGIN INSERTIONTemporal fossa & temporal fascia

Coronoid process and anterior border of ramus

•Largest and most powerful muscle of mastication•Fan shaped muscle•Fibres are vertical and horizontal- accounts for different actions this muscle can perform.•Often visible when chewing

Anterior and superior fibers elevate mandible

Posterior fibers retract mandible

NERVE SUPPLY •Nerve to medial pterygoid (branch. of main trunk of Mandibular Nerve)

ORIGIN INSERTION

Superficial Maxillary tuberosity

Medial surface of angle of mandible

Deep Medial surface of lateral ptergoid plate

Mylohyoid groove

•Elevates & Protrudes mandible, also causing jaw closure

ACTION OF MEDIAL PTERYGOID

•Unilateral contraction – mediotrusive movement of the mandible

Most commonly involved in MYOFACIAL PAIN DYSFUNCTION SYNDROME

Trismus following inferior alveolar nerve block is mainly due to involvement of medial pterygoid muscle

ORIGIN INSERTIONUPPER HEAD

Infratemporal surface of crest of greater wing of sphenoid

Pterygoid fovea

LOWER HEAD

Lateral surface of lateral pterygoid plate

Articular surface and capsule of TMJ

NERVE SUPPLY• Branch of anterior division of mandibular nerve

•Depresses mandible

On unilateral contraction causes the lateral movement of mandible to the opposite side

•Along with medial pterygoid protrudes mandible

Most commonly involved muscle in MYOFACIAL PAIN DYSFUNCTION SYNDROME

Unilateral failure of lateral pterygoid muscle to contract results in deviation of the mandible toward the affected side on opening

Bilateral failure results in limited opening, loss of protrusion & loss of full lateral deviation

NERVE SUPPLY

•Anterior belly-mylohyoid

branch of inferior alveolar

nerve

•Posterior belly-Facial nerve

ORIGIN INSERTION

Anterior Belly

Posterior Belly

Digastric fossa

Mastoid notch

Tendon attached to body & greater cornua of hyoid bone

•Depresses mandible while

opening mouth

•Elevates hyoid bone

during swallowing

NERVE SUPPLY:

Mylohyoid branch of inferior

alveolar nerve

ORIGIN INSERTION Mylohyoid line of mandible

Postreior fibers-to body of hyoid boneMiddle & anterior fibers-decussate to form fibrous band

•Depresses mandible while opening mouth

•Elevates hyoid bone and floor of mouth during deglutition

NERVE SUPPLY 1ST cervical spinal nerve through Hypoglossal nerve

ORIGIN INSERTION

Inferior Genial Tubercle of mandible

Anterior surface of hyoid bone

•Depresses mandible while opening mouth

•Eelevates hyoid bone

Sternohyoid•Depresses hyoid bone

Sternothyroid•Depresses larynx

Thyrohyoid•Depresses hyoid bone•Elevates larynx

Omohyoid•Depresses hyoid bone & larynx•Carries hyoid bone backwards & to the side

ARTERIAL SUPPLY- MAXILLARY ARTERY-2ND PART(TERMINAL BRANCH OF ECA)

VENOUS DRAINAGE-RETROMANDIBULAR VEIN

LYMPHATIC DRAINAGE- SUBMANDIBULAR & SUBLINGUAL LYMPH NODES.

PAIN-Compromised

No PAIN-Healthy

Palmar surface of middle, index, fore

finger used for palpation

LEFT & RIGHT palpated

simultaneously

ANTERIOR FIBERS-ABOVE

THE ZYGOMATIC ARCH,ANTERIOR

TO TMJ

MIDDLE REGION-ABOVE

TMJ,SUPERIOR TO ZYGOMATIC

ARCHPOSTERIOR FIBERS-ABOVE & BEHIND

THE EAR

Fingers placed on each side of

zygomatic arch,just anterior to the TMJ

Fingers dropped down slightly to the portion

of masseter attached to zygomatic arch

Palpated bilaterally,at superior & inferior attachments

The fingers drop to the inferior attachment on the inferior border of the ramus

INTRAORAL METHOD Palpated by sliding finger lingually and by applying pressure at the insertion of muscle above the angle of mandible

Superior head – equal pressure on lateral poles of condyle as patient opens and closes his mouth

Inferior head- Placing the forefinger, over the buccal area of the maxillary third molar region & slide in medial direction behind the maxillary tuberosity

Many anatomical and clinical studies have demonstrated the inability to digitally contact the Lateral pterygoid muscle due to its location and surrounding tissues.

CONTRACTING

Protruding against resistance – increases pain

STRETCHING• Clenching on teeth–

increases pain.• Clenching on

separator–no pain

INFERIOR LATERAL PTERYGOID

SUPERIOR LATERAL PTERYGOID

CONTRACTION• Clenching on teeth –

increases pain.• Clenching on separator –

increases pain

STRETCHING• Clenching on teeth –

increases pain.• Clenching on separator –

increases pain• Opening mouth – no pain

CONTRACTION• Clenching on teeth –

increases pain.• Clenching on separator –

increases pain

STRETCHING

Opening mouth – increases pain

MEDIAL PTERYGOID

If a second stimulus is given before the muscle comes to a relaxed

state the muscle does not respond for the second stimulus of

whatever strength it might be. This period of inactivity where the

muscle does not respond is termed as Massetric silent period

A part of the complex feedback mechanism of mandibular control

involving receptors in the periodontal ligament and muscles.

Journal of Oral Rehahilitation 1995 22; 49-55

A) MYOTACTIC REFLEX MONOSYNAPTIC REFLEX

Sudden downward force applied to the chin with a small rubber hammer

This will cause the jaw to be reflexly elevated resulting in masseter contraction and tooth contact

When a skeletal muscle is quickly stretched, this

protective reflex brings about a contraction of the stretched

muscle

B)NOCICEPTIVE REFLEX POLYSYNAPTIC REFLEX

Hard object is suddenly encountered during

mastication

Jaw quickly drops and the teeth are pulled away from the

object

Protects the teeth and supportive structures from damage created by sudden and unusually heavy forces

MASSETER/MONOSYNAPTIC reflex•Used to test the status of a patients trigeminal nerve

Masseter muscle will jerk the mandible upwards

The mandible is tapped at a downward angle just below the lips at the chin while mouth is held slightly open

Upper motor neuron lesion-pronounced reflex

POLYSYNAPTIC REFLEX

RESULT OF MECHANICAL/ELECTRICAL

STIMULATION OF LIPS,ORAL MUCOSA OR TEETH

A SLIGHT OPENING MOVEMENT OCCURS DUE TO INHIBITION OF ACTIVITY IN THE

MANDIBULAR ELEVATORS WITHOUT SIMULTANEOUS CONTRACTION OF

DEPRESSORS

PROTECTIVE REFLEX

ON SUDDEN ENCOUNTER WITH A HARD

OBJECT,MASTICATION IS STOPPED

REFLEX INHIBITION OF ELEVATORS +

REFLEX EXCITEMENT OF DEPRESSORS

DUE TO PDL RECEPTORS

PROTECTS TEETH FROM DAMAGE

REFLEX CHANGES OCCURING IN ELEVATOR MUSCLES WHEN UPPER

& LOWER TEETH ARE SNAPPED TOGETHER

TRANSIENT ACTIVATION > SILENT PERIOD > PHASE OF INCREASED

& DECREASED ACTIVITY OF ELEVATOR MUSCLES

NO EFFECTS ON THE DEPRESSORS

LATERAL,PROTRUSIVE & RETRUSIVE REFLEX

MANDIBULAR REFLEXES

The average maximum sustainable biting force is 756N (170 pounds)

Normal Dentition:80 NDentures: 64N

Males: 520N Females: 350N

Incisor region: 89-111 NCuspid region: 133-334 N

Premolar region:222-445 NMolar region: 400-890 N

15 Chews in a series from the time of food entry until

swallowing

Average jaw opening during chewing is between 16-20mm

Average lateral displacement on chewing is between 3-

5mm

Duration of masticatory cycle varies between 0.6 and 1

sec

Men chew faster and have a shorter occlusal phase than

women,it also depends on the type of food

Have shorter contraction time than most other body muscles

Incorporate more of muscle spindles to monitor their activity

Do not have golgi tendon organs to monitor tension Do not fatigue easily Psychological stress increases the activity of jaw closing

muscles Occlusal interferences cause a hypertonic synchronous

muscle activity Closing movement also determined by the height of the

teeth

MASTICATORY ENVELOPE

“TEAR- DROP SHAPE”

•Slight displacement at the beginning of the opening phase

•In most cases it deviates to the chewing side

•The maximum extent of vertical and lateral movement in normal masticaton is about half of the maximum vertical and lateral movement possible.

ATROPHY: Decrease in the mass of the muscle; it can be a partial or complete wasting away of muscle.

HYPERTROPHY : Involves an increase in mass of  a muscle through an increase in the size of its component cells.

HYPERPLASIA: Increase in number of muscle fibers due to extreme muscle force generation

Initial response of a muscle to altered sensory or proprioceptive input or injury.

Antagonistic muscle groups seem to fire during movement in an attempt to protect the injured part.

Increased activity of the jaw – opening muscles during closure and an increase in closing muscle activity during mouth opening.ETIOLOGY- Altered sensory or proprioceptive input, Constant deep pain input, Increased emotional stress

Eliminate etiology either by correction of functional discrepancies or relieving stress

Structural dysfunction – velocity and range of mandibular movement is decreased

Minimal pain at rest & Increased pain with function

Feeling of muscle weakness

CLINICAL FEATURES

Acquired auto immune disorder of neuromuscular

transmission characterized by muscle weakness.

Antibodies to Acetyl choline receptor on skeletal muscle fiber

Protrusive movement of the tongue becomes weakDysphagiaDysarthriaImpaired salivationMuscle fatigueFacal paralysis

SYMPTOMS

•Dental procedure- after 1-2 hours following intake of medicine, •Preferably in the morning•Stress reduction prior to dental treatment

MANAGEMENT

Glossary of Prosthodontic Terms (GPT-8) defines BRUXISM as 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.

ETIOLOGY:•STRESS

•PSYCHOLOGICAL DISTURBANCES

•BITE DISCREPANCIES AND TEMPEROMANDIBULAR DISORDERS

•NUTRITIONAL DEFICIENCIES

CLINICAL FEATURES•Occlusal wear•Periodontal destruction•Muscular hypertrophy and tenderness•HeadacheTreatment : •Coronoplasty •Occlusal splints

Journal of Prosthodontic Research 55 (2011) 127–136

•When prosthetic intervention is indicated in a patient with bruxism, efforts should be made to reduce the effects of likely heavy occlusal loading on all the components that contribute to prosthetic structural integrity. •Failure to do so may indicate earlier failure than is the norm.

DIFFERENT DEGREES OF LATERAL PTERYGOID

HYPERACTIVITY

Causes :

•Intracapsular :Arthritis,

condylar fractures

•Pericapsular –

irradiation, dislocation,

infection and inflammation

•Muscular – TMJ

dysfunction syndrome,

tetanus (lock jaw

•Others – systemic

sclerosis, fracture TRISMUS LEADS TO:•Difficulty in eating, maintaining oral hygiene, in speech & swallowing

•Joint immobilization

TREAT THE UNDERLYING CAUSE

JAW OPENING EXERCISES

SYMPTOMATIC RELIEF

•Sectional impression trays and Sectional dentures

PROSTHODONTIC MANAGEMENT

J Prosthet Dent. 2000 Sep;84(3):269-73

Vinyl polysiloxane occlusal-registration material mixed in an automix dispenser - superior flow, ease of mixing, convenient dispensary,rigidity, and quick-setting properties, which allow it to be used in the mandibular arch successfully as a custom-diagnostic impression tray

J Prosthet Dent. 2000 Sep;84(3):269-73

In the maxillary arch, the diagnostic impression is made using a combination of wooden spatula, thermoplastic modeling plastic impression compound, and irreversible hydrocolloid.

The modeling plastic impression compound is more viscous and it prevents slumping when it is being used in the maxillary arch

Because of the relatively simple anatomy on the maxillary arch, the modeling plastic provides enough working time to capture the required anatomic landmarks This molding procedure should be performed in an incremental manner to ensure that the modeling plastic impression compound is retrievable

If the modeling plastic impression tray becomes too large to be retrieved, it can be broken down into smaller pieces and carefully removed from the oral cavity.

•Border molding in such a situation should be re-attempted using elastomeric material. •The rest of the clinical procedures follow traditional complete denture fabrication. No change in the laboratory phase is needed

J Prosthet Dent. 2000 Sep;84(3):269-73

Preliminary impressions were madewith polyvinyl siloxane putty material-Flexible impression tray technique

Two-piece custom tray design with sections of the tray that can be joined firmly and oriented accurately both in patient’s mouth and after removal of the tray from the mouth.

Impression is made by orienting the respective sections of the trays with the help of a lock system or screw,

And then unlocking it inorder to take it out of the mouth,again rejoining outside the mouth for further lab procedure

Mastication is oral motor behavior reflecting central

nervous system commands, and many peripheral sensory

inputs to modulate the rhythmic jaw movements.

Since tooth guidance has an enormous influence on

muscle activity during chewing and swallowing, it is

advisable to make restorations and replacements as much

compatible as possible, with the functional movement

patterns of the patient, rather than expect the patterns of

the mastication to adapt to the new made replacements.

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Brain

•G.H. Sperber. Craniofacial embryology.

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physiology.10th edition,Harcourt Asia PTE LTD.

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Physiology,Eighteenth edition 1997

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Edentulous Patients, twelth edition 2004

•Sheldon Winkler,Essentials of complete denture

Prosthodontics,second, edition 2000.

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and occlusion.5th edition. St Louis: Mosby Publishing.

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2nd edn, Peter Dawson John W. E. Snawdon Fibrositis in the

Muscles of Mastication(With Reference to the Masseter Muscle)

•Proc R Soc Med. 1949 ; 42(3): 153–154 Yasmin et al Published

online 2013 doi:  10.1186/1745-6215-14-316

•The Glossary of Prosthodontic Terms

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management of limited oral access after ablative tumor surgery: a

clinical report. J Prosthet Dent. 2000 84(3):269-73.

•Johansson A, Omar R, Carlsson G.E Bruxism and prosthetic

treatment: A critical review Review Article

Journal of Prosthodontic Research, Volume 55, Issue

3, 2011, Pages 127-136.

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