muscles of mastication ppt
TRANSCRIPT
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GOOD MORNING
LAB
WORK
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ANISH YOGESH AMIN
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INTRODUCTION TYPES OF MUSCLE FIBERS
FUNCTIONS OF MUSCLE
FIBERS
REFLEX MECHANISMS
PROSTHODONTIC IMPLICATIONS
MASTICATORY MUSCLES
CONCLUSIONDISORDERS OF
MASTICATORY MUSCLES
REFERENCES
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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
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ISOTONIC CONTRACTION
ISOMETRIC CONTRACTION
CONTROLLED RELAXATION
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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
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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
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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
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“MANDIBULAR
ARCH”
The basic muscles of mastication develop from the mesenchyme of first branchial arch
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MASTICATION
Mastication (1649): Process of chewing food for swallowing and digestion
GLOSSARY OF PROSTHODONTIC TERMS 8
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Four major muscles Masseter Temporalis Medial pterygoid(internal) Lateral pterygoid (external)
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• DIGASTRIC
• MYLOHYOID
• GENIOHYOID
• INFRAHYOID
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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
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•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)
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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
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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
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•\
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
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Anterior and superior fibers elevate mandible
Posterior fibers retract mandible
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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
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•Elevates & Protrudes mandible, also causing jaw closure
ACTION OF MEDIAL PTERYGOID
•Unilateral contraction – mediotrusive movement of the mandible
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Most commonly involved in MYOFACIAL PAIN DYSFUNCTION SYNDROME
Trismus following inferior alveolar nerve block is mainly due to involvement of medial pterygoid muscle
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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
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•Depresses mandible
On unilateral contraction causes the lateral movement of mandible to the opposite side
•Along with medial pterygoid protrudes mandible
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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
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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
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•Depresses mandible while
opening mouth
•Elevates hyoid bone
during swallowing
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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
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•Depresses mandible while opening mouth
•Elevates hyoid bone and floor of mouth during deglutition
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NERVE SUPPLY 1ST cervical spinal nerve through Hypoglossal nerve
ORIGIN INSERTION
Inferior Genial Tubercle of mandible
Anterior surface of hyoid bone
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•Depresses mandible while opening mouth
•Eelevates hyoid bone
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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
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ARTERIAL SUPPLY- MAXILLARY ARTERY-2ND PART(TERMINAL BRANCH OF ECA)
VENOUS DRAINAGE-RETROMANDIBULAR VEIN
LYMPHATIC DRAINAGE- SUBMANDIBULAR & SUBLINGUAL LYMPH NODES.
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PAIN-Compromised
No PAIN-Healthy
Palmar surface of middle, index, fore
finger used for palpation
LEFT & RIGHT palpated
simultaneously
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ANTERIOR FIBERS-ABOVE
THE ZYGOMATIC ARCH,ANTERIOR
TO TMJ
MIDDLE REGION-ABOVE
TMJ,SUPERIOR TO ZYGOMATIC
ARCHPOSTERIOR FIBERS-ABOVE & BEHIND
THE EAR
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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
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INTRAORAL METHOD Palpated by sliding finger lingually and by applying pressure at the insertion of muscle above the angle of mandible
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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.
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CONTRACTING
Protruding against resistance – increases pain
STRETCHING• Clenching on teeth–
increases pain.• Clenching on
separator–no pain
INFERIOR LATERAL PTERYGOID
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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
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CONTRACTION• Clenching on teeth –
increases pain.• Clenching on separator –
increases pain
STRETCHING
Opening mouth – increases pain
MEDIAL PTERYGOID
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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
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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
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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
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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
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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
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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
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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
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LATERAL,PROTRUSIVE & RETRUSIVE REFLEX
MANDIBULAR REFLEXES
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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
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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
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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
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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.
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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
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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
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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
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Acquired auto immune disorder of neuromuscular
transmission characterized by muscle weakness.
Antibodies to Acetyl choline receptor on skeletal muscle fiber
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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
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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.
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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
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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.
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DIFFERENT DEGREES OF LATERAL PTERYGOID
HYPERACTIVITY
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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
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TREAT THE UNDERLYING CAUSE
JAW OPENING EXERCISES
SYMPTOMATIC RELIEF
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•Sectional impression trays and Sectional dentures
PROSTHODONTIC MANAGEMENT
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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
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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
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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
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Preliminary impressions were madewith polyvinyl siloxane putty material-Flexible impression tray technique
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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.
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Impression is made by orienting the respective sections of the trays with the help of a lock system or screw,
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And then unlocking it inorder to take it out of the mouth,again rejoining outside the mouth for further lab procedure
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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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•Gray’s anatomy.
•B .D Chaurasia’s. Human Anatomy . Head , neck and
Brain
•G.H. Sperber. Craniofacial embryology.
•Guyton and hall.2001.Textbook of medical
physiology.10th edition,Harcourt Asia PTE LTD.
•William F Ganong,Review of Medical
Physiology,Eighteenth edition 1997
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•George A.Zarb,Charles L Bolender,Prosthodontic Treatment for
Edentulous Patients, twelth edition 2004
•Sheldon Winkler,Essentials of complete denture
Prosthodontics,second, edition 2000.
•Okeson JP.2002 Management of temporomandibular disorders
and occlusion.5th edition. St Louis: Mosby Publishing.
•Evaluation , diagnosis and treatment of occlusal problems –
2nd edn, Peter Dawson John W. E. Snawdon Fibrositis in the
Muscles of Mastication(With Reference to the Masseter Muscle)
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•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
•Cheng AC, Wee AG, Shiu-Yin C, Tat-Keung L. Prosthodontic
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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THANK YOU