temporomandibular joint anatomy and its prosthodontic implications
TRANSCRIPT
GOOD AFTERNOON
TEMPOROMANDIBULAR JOINT ANATOMY
PRESENTED BY:
FALAK NAZPG 1ST YEAR DEPTT OF PROSTHODONTICS, CROWN &BRIDGE,GDC SGR
CONTENTS INTRODUCTION DEFINITION PECULIARITY OF TMJ DEVELOPMENT ANATOMIC COMPONENTS VASCULAR SUPPLY INNERVATIONS MOVEMEN BIOMECHANICS PROSTHODONTIC IMPLICATIONS REFERENCES
INTRODUCTION
ACCORDING TO GPT 8
A JOINT is•The place of union
of two or more bones—GPT 8
A. FibrousB. CartilaginousC. Synovial
Joints can be classified as;
DEFINITION
The articulation between the temporal bone and the mandible.
It is a bilateral diarthrodial, bilateral ginglymoid joint—
GPT 8
Also known as CRANIO-
MANDIBULAR ARTICULATION
Considered as a ginglymoarthrodial SYNOVIAL joint
Classified as a compound joint
Multiaxial joint
Peculiarity of TMJ
1. Bilateral diarthrosis
2. Articular surface covered by fibrocartilage instead of hyaline cartilage
3. Only joint in human body to have a rigid endpoint of closure
Peculiarity of TMJ…….
4. In contrast to other diarthrodial joints TMJ is last joint to start develop, in about 7th week in utero.
5. Develops from two distinct blastema.
At week 12 of gestation: TEMPORAL OR GLENIOD BLASTEMA Ossifies and becomes glenoid fossa
CONDYLAR BLASTEMA Becomes the condylar cartilage
Clefts are formed lower joint cavity upper joint cavity
DEVELOPMENT
1.Primitive articular disc
2.Upper cleft3.Lower cleft4.Temporal
blastema5. Condylar
blastema
A - Fibrous layerB - Reserve zone
C - Proliferative zone
D - Hypertrophic zone
E - Calcifying zone
F - Bone
{HISTOLOGY}
AnatomicComponents
COMPONENTS
PASSIVE BONY COMPONENTS JOINT CAPSULE LIGAMENTS DISC
ACTIVE MUSCLES
CRANIAL COMPONENT
Articular fossa
MUSCLE
AREA OF INTEREST
LIGAMENT DISC
MANDIBULAR COMPONENT
condyle
INDIVIDUAL COMPONENTSBONE- Fossa mandibularis ossis
temporalis - Capitulum mandibula
(condyle )- Tuberculum articulare ( articular eminence )
CAPSULE & LIGAMENTS
ARTICULAR DISC
MUSCULAR COMPONENT
THE MANDIBULAR CONDYLEProcessus condyloideus -Mediolateral : 15 – 20 mm-Anteroposterior : 8 – 10 mm
-Anterior view : medial & lateral poles, the medial pole more prominent
-The actual articulating surface ~ extends anteriorly and posteriorly to the most superior aspect ( P > A )
NECK CONSIDERED AS FUSE BOX OF CONDYLE
If the long axes of two condyles are extended medially, they meet at approximately the basion on the anterior limit of the foramen magnum, forming an angle that opens toward the front ranging from 145° to 160°
The articular surface lies on its anterosuperior aspect, thus facing the posterior slope of the articular eminence of the temporal bone.
E: Articular eminence; ENP: entogolenoid process; t:articular tubercle; CO: condyle; POP: postglenoid process; LB: lateral border of the mandibular fossa; PEP: preglenoidplane; GF: glenoid fossa; CP: condylar process
-
MANDIBULAR FOSSATHE SQUAMOUS PORTION OF THE TEMPORAL BONE (CONCAVE )
ANTERIOR : A CONVEX BONY PROMINENCE ( TUBERCLE ) = ARTICULAR EMINENCE
POSTERIOR : SQUAMOTYMPANIC FISSURE (M-L) ~ ANTEROMEDIAL : PETROSQUAMOUS FISSURE ~ POSTEROMEDIAL : PETROTYMPANIC FISSURE
E: Articular eminence; ENP: entogolenoid process; t:articular tubercle; Co: condyle; pop: postglenoid process; lb: lateral border of the mandibular fossa; PEP: preglenoidplane; GF: glenoid fossa; Cp: condylar process
The posterior roof is thin ~ not designed to sustain heavy force
The articular eminence consists of thick dense bone ~ to tolerate such forces
The steepness of the articular eminence surface ~ dictates the pathway of the condyle -CONDYLAR GUIDANCE.
Medial poles located in medial third of the fossa
This is the entire transverse bony bar that forms the anterior root of zygoma.
Articular eminence:
This articular surface is most heavily traveled by the condyle and disk as they ride forward and backward in normal jaw function
Mandibular condyle
Squamous temporal bone
Articular eminence
It is a BICONCAVE FIBROCARTILAGINOUS structure located between the mandibular condyle and the temporal bone.
It FUNCTIONS to accommodate a hinging action as well as the gliding actions .
ARTICULAR DISC
The ARTICULAR DISC is a roughly oval, firm, fibrous plate.
PARTS:1. ANTERIOR BAND = 2 mm
thick 2. POSTERIOR BAND = 3
mm thick, 3. INTERMEDIATE BAND of 1
mm thickness.
4.More posteriorly there is a BILAMINAR OR RETRODISCAL REGION.
• SHAPED like a PEAKED CAP that divides the joint into a
larger upper compartment and a smaller lower compartment.
• Hinging movements take place in the lower compartment and gliding movements take place in the upper compartment.
• The superior surface of the disc - SADDLE-SHAPED to fit into the cranial
contour,
• The inferior surface - CONCAVE to fit against the mandibular
condyle.
ATTACHMENTS OF DISC
•POSTERIORLY: RETRODISCAL TISSUE
- It is a loose connective tissue region that is highly vascularized and innervated.
AV SHUNT ALSO k/aVASCULAR KNEE
SUPERIOR : superior retrodiscal lamina ( CONTAINS MAINLY ELASTIC FIBERS ] It attaches the disc posteriorly to the tympanic plate It prevents slipping of the disc while yawning.
INFERIOR : inferior retrodiscal lamina ( COMPOSED CHIEFLY COLLAGENOUS FIBERS ) It attaches the inferior border of the posterior edge of the disc to the posterior margin of the articular surface of the condyle. It prevents excessive rotation of the disc over the condyle.
ANTERIORLY:Anterior region of the disc is attached to the capsular ligament - Anterio-Superior : anterior margin of the articular surface of the temporal bone -Anterio-Inferior : anterior margin of the articular surface of the condyle Anteriorly the disc is also attached by tendinous fibers to the superior lateral pterygoid muscle
ON SAGITTAL MR IMAGING, THE DISK - biconcave structure with homogeneous low signal intensity.
The anterior band lies immediately in front of the condyle
• posterior band and retrodiskal tissue are best depicted in the open-mouth position.
Lubrication of the Joint
Comes from Synovial fluid
The synovial fluid comes from two sources: first, from plasma by dialysis, and second, by secretion from type A and B synoviocytes)
Contrast radiography studies have estimated that the upper compartment could hold approximately 1.2 ml of fluid without undue pressure being created, while the lower has a capacity of approximately 0.9ml.
It is clear, straw-colored viscous fluid. It diffuses out from the rich cappillary network
of the synovial membrane.
Contains: Hyaluronic acid which is highly viscous May also contain some free cells mostly
macrophages.
Functions: Lubricant for articulating surfaces. Carry nutrients to the avascular tissue of the
joint. Clear the tissue debris caused by normal wear
and tear of the articulating surfaces.
Two mechanisms of the lubrication :1. Boundary lubrication Prevents friction in the moving joint2. Weeping lubrication Eliminates friction in the compressed but
not moving joint
LIGAMENTS
PRIMARY LIGAMENTS1.Capsula articularis ~ CAPSULAR LIGAMENT - THIN SLEEVE OF FIBROUS TISSUE surrounding
the entire TMJ - Superior attachment ~ the borders of the articular surface of the mandibular fossa and articular eminence - Inferior attachment ~ collum mandibula
This capsule is reinforced more laterally by an external TMJ ligament, which also limits the distraction and the posterior movement of the condyle.
Medially and laterally- blends with the condylodiscal ligaments.
Anteriorly, the capsule has an orifice through which the lateral pterygoid tendon passes. This area of relative weakness in the capsular lining becomes a source of possible herniation of intra-articular tissues, and this, in part, may allow forward displacement of the disk.
- Function : ~ to resist any medial,
lateral or inferior forces that tend to separate or dislocate the
articular surface
~ to retain the synovial fluid ~ propioception
2.Collateral ( discal ) ligaments - From medial and lateral borders of the disc to
the poles of the condyle ~ the medial discal ligament ~ the lateral discal ligament - Dividing the joint mediolaterally into superior
and inferior joint cavities
Permit the disc to be rotated A-P on the articular surface of the condyle
These ligaments are RESPONSIBLE FOR THE HINGING MOVEMENT BETWEEN THE CONDYLE AND THE ARTICULAR DISC
- They have a vascular supply and are innervated
- Function : Allow the disc to move passively with
the condyle as it glides A - P
3.Temporomandibular ligament - It lies at the lateral aspect of the capsular
ligament - Composed of two parts : Outer oblique portion From the outer surface of the articular tubercle and zygomatic process postero inferiorly to the outer surface of the condylar neckFUNCTION ~ it resists excessive dropping of the
condyle so limiting the extent of mouth opening
A, As the mouth opens, the teeth can be separated about 20 to 25 mm (from A to B)without the condyles moving from the fossae. B, TM ligaments are fully extended. As themouth opens wider, they force the condyles to move downward and forward out of thefossae. This creates a second arc of opening (from B to C).
Inner horizontal portion From the outer surface of the articular
tubercle and zygomatic process posteriorly and horizontally to the lateral pole of the condyle and posterior part of the articular disc.
FUNCTION ~ It limits posterior movement of the
condyle and discUNIQUE FEATURE OF TML:LIMITS ROTATIONAL MOVEMENT ---FOUND ONLY IN HUMAN
ACCESORY LIGAMENTS4.Sphenomandibular ligament From the spine of the sphenoid bone & extends downward to lingula mandibula
5.Stylomandibular ligament - The second accesory
ligament. - This is a specialized
dense, local concentration of deep cervical fascia
- From the styloid process & extends downward and forward to the angle and
posterior border of the ramus mandibula.
-FUNCTION It limits excessive protrusive movements of
the mandible
This ligament becomes tense only in extreme protrusive movements.
DISCO-MALLEOLAR LIGAMENT
The disco malleolar ligament (PINTO LIGAMENT) was described by pinto(1962) as a connection between the malleus & the medial wall of joint capsule.
However, a separate ligament can be demonstrated here in only 29% of temporo mandibular joints .
MUSCULAR COMPONENT
PRIMARY MUSCLES OF MASTICATION
• MASSETER • TEMPORALIS • LATERAL
PTERYGOID • MEDIAL
PTERYGOID
SECONDARY MUSCLES OF MASTICATION
•Suprahyoid muscles •Infrahyoid muscles
SUPRAHYOID GROUP
•DIGASTRIC •MYLOHYOID •GENIOHYOID •STYLOHYOID
INFRAHYOID MUSCLES
STERNOHYOID THYROHYOID OMOHYOID
STERNOCLEIDOMASTOID AND TRAPEZIUS
&
Skeletal Voluntary Multipennate Quadrate Antigravity Elevator
MASSETER
ELEVATION Of MANDIBLE By MASSETER
TEMPORALIS FAN SHAPED BIPENNATE MUSCLE SKELETAL VOLUNTARY
Anterior fibers ELEVATIONPosterior fibers RETRUSION
Functions of temporalis muscle
a Thick muscle Quadrate Multipennate Skeletal Voluntary
MEDIAL PTERYGOID or INTERNAL PTERYGOID
PTERYGOIDEUS MEDIALIS Consists 2 heads ( caput ) - Caput superficial -Caput profundus
FUNCTION:- Contraction ~ mandible is
ELEVATED and the teeth are brought into contact
- It is also active in PROTRUDING the mandible
- Unilateral contraction ~ mediotrusive movement of the MANDIBLE
LATERAL PTERYGOIDPTERYGOIDEUS LATERALIS It consists 2 heads or bellies with different functionCaput superiorCaput inferior
FUNCTION :-While the inferior active during opening, the superior remains inactive, becoming active only in conjunction with the elevator
-The superior lateral pterygoid active during power stroke
BLOOD SUPPLY
ARTERIES: BRANCHES FROM SUPERFICIAL
TEMPORAL AND MAXILLARY ARTERIES VEINS: VEINS FOLLOW ARTERIES
INNERVATION Movements of synovial joint are initiated & effected by
muscle coordination. Achieved in part through sensory innervation. Hilton’s Law: The muscles acting on a joint have the same nerve supply
as the joint. Therefore:
Branches of the mandibular division of the fifth cranial nerve supply the TMJ (auriculotemporal, deep temporal, and masseteric) supply the joint.
MOVEMENTS
Movements
Rotational / hinge movement in first 20-25mm of mouth opening
Translational movement after that when the mouth is excessively opened.
1. Depression Of Mandible Lateral pterygoid Digrastric Geniohyoid Mylohyoid
2. Elevation of Mandible Temporalis Masseter Medial Pterygoids
3. Protrusion of Mandible Lateral Pterygoids Medial Pterygoids
4. Retraction of Mandible Posterior fibres of Temporalis
1. History taking2. Measuring maximum interincisal opening3. Palpation of pretragus area ; the lateral aspect of
TMJ4. Intra – auricular palpation ; the posterior aspect of
TMJ5. palpation of masseter muscle6. Palpation of lateral pterygoid muscle7. Palpation of medial pterygoid8. Palpation of temporalis
CLINICAL EXAMINATION OF TMJ
•The maximum opening distance between the incisal edges of upper and lower incisor is measured using scale , Boley gauge or ruler•Normal opening – 40 to 55 mm
•Normal opening can also be estimated by patient’s own finger•Normal : three finger end on end•Two finger opening reveals reduction in opening but not necessarily reduction in function•One finger opening indicates reduced function
Normal lateral range of movement is >7-10mm
PROTRUSIVE-10-14mm
Palpation of pretragus area ; the lateral aspect of TMJ
TMJ can also be palpated through anterior wall of external auditory meatus
PALAPATION OF MUSCLES
Temporalis muscle can be seen and readily palpated throughout entire length and breadth when the patient’s teeth are firmly clenched.
Palpate multiple areas ofthe masseter muscle
PALAPTION OF MASSETER
As with temporalis muscle,it can be located when patient’s jaw are forcibly
PALPATION OF MEDIAL PTERYGOIDAnterior part of insertion can be palpated by placing the finger at 45 degrees in the floor of the patients mouth near base of the relaxed tongue.The opposite hand can be used to extraorally to palpate posterior and inferior portions of insertion.Body of the muscle can be palpated by rotating the index finger upwards against the muscle to near its origin on the tuberosity.
PALPATION OF LATERAL PTERYGOID MUSCLEThe muscle is palpated by using the little or index finger and placing it lateral to maxillary tuberosity and medial to coronoid process.The finger presses upwards and inwards and a painful response can be determined .
PROSTHODONTIC IMPLICATIONS& BIOMECHANICS OF TMJ
Definition
Study of function and structure of biological system
-BIOMECHANICS
Two joint systems in one joint
Condyle Disc complex ROTATIONAL MOVEMENT
Condyle disc complex functioning against the fossa TRANSLATORY MOVEMENTS
At rest condyle rests on posterior band; beginning of translation, it lies over the intermediate zone; when mouth is fully open, it lies over the anterior band.
STOMATOGNATHIC SYSTEM
TMJ
TEETH
Why study TMJ as a prosthodontist
BASIC PRINCIPLE--Dawson•Neuromuscular harmony depends on structural harmony between the occlusion and temporomandibular joints.
Occlusal harmony must for healthy TMJ
PRIMARY REQUIREMENTS FOR SUCCESSFUL OCCLUSAL THERAPY
----stable TMJ----non interfering post.teeth----anterior teeth in harmony with envelope of function
MASTICATORY MUSCLE FUNCTION IS AFFECTED BY THE OTHER 3 STRUCTURES.
•OCCLUSAL INTERFERENCES require
•DISPLACEMENT OF TMJ (to achieve max.intercuspation)&
•Cause INCORDINATION OF MASTICATORY MUSCULATURE
OCCLUSO MUSCLE PAIN
Occlusal dysharmony , most common cause of TMD PAIN in patients seeking prosthetic rehabilitation
High points or deflective tooth inclines Muscle hyperactivity Pain
A PERMISSIVE (SMOOTH) ANTERIOR SPLINT SEPARATES THE INTERFERINGMOLAR FROM CONTACT, THUS PERMITTING THE CONDYLE DISK ASSEMBLIES TOSEAT UP INTO CENTRIC RELATION. THIS ELIMINATES THE TRIGGER FOR MUSCLE ACTIVITYAND ALLOWS THE INFERIOR LATERAL PTERYGOID MUSCLE TO RELEASE. PEACEFUL, COMFORTABLE MUSCLE ACTIVITY RESUMES QUICKLY.
Posterior occlusal interference: When any posterior toothinterferes with the anterior guidance in eccentric movement, the lateralpterygoid muscles are activated and the elevator muscles are hyperactivated.This results in incoordinated muscle hyperfunction. It also puts theposterior teeth in jeopardy of horizontal overload, and subjects them to excessiveattritional wear, fractures, and hypermobility.
CENTRIC RELATION & TMJCENTRIC RELATION IS THE RELATIONSHIP OF THE MANDIBLE TO THE MAXILLA WHEN THE PROPERLY ALIGNED CONDYLE-DISK ASSEMBLIES ARE IN THE MOST SUPERIOR POSITION AGAINST THE EMINENTIAE IRRESPECTIVE OF VERTICAL DIMENSION OR TOOTH POSITIONGPT 8
HOW MANDIBLE GOES INTO CENTRIC RELATION
TRIAD OF STRONG ELEVATOR MUSCLES pulls the condyle-disk assemblies up the slippery posterior
slopes of the eminentiae.
The INFERIOR LATERAL PTERYGOID releases and stays released through complete closure
Complete upward seating of the condyles
CENTRIC RELATION
A:SUPERFICIAL MASSETER pulls the condyle against the posterior slope and up. …..
B: The INTERNAL PTERYGOID PULL THE CONDYLES UP from the lingual side of the mandible. …..
C:The DEEP FIBERS OF THE MASSETER PULLTHE CONDYLE UP…..
D:The TEMPORALIS attach to the coronoid process between the teeth and the TMJs and PULL THE CONDYLE UP……
A B
C D
RELEASE OF INFERIOR LATERAL PTERYGOID
MOST COMMONLY ENCOUNTERED SIGNS ND SYMPTOMS AFFECTING TMJ IN A PROSTHETIC SET UPJOINT SOUNDSJOINT RESTRICTIONSOCCLUSAL DISCREPENCIESDYSHARMONY BETWEEN CENTRIC RELATION & OCCLUSIONBRUXISMEMOTIONAL STRESS (MOSTLY IN EDENTULOUS PATIENTS)
A BRIEF ABOUT OCCLUSAL SPLINTS
OCCLUSAL SPLINTS
An occlusal splint is a removal device made of hard acrylic creating precise occlusal contact with the teeth of the opposing arch.
Temporarily provide an orthopedically musculoskeletal stable joint position.
Used to introduce an optimum occlusal condition that recognizes the neuromuscular reflex activity.
Used to protect teeth from excessive tooth wear.
USES OF OCCLUSAL SPLINTS
Types Of Occlusal Appliances
The two most commonly used are:1. The stabilization appliance2. The anterior positioning appliance
INDICATIONS
Stabilization appliance are generally used to treat muscle pain disorders.
Anterior positioning appliance are used for treatment of disc derangement disorders.
Bruxism is the most common reason for making a splint .
Considerations before making a splint
Counseling, behavioral therapy, relaxation training etc. may work as well or even better than a splint.
Age dependant wear is natural and does not require splint protection.
Physiotherapeutic exercise can also sometimes treat the disorder.
A maxillary Occlusal Splint is the type used .
An impression is recorded and a cast is prepared.
This is followed by adaptation of a 2mm thick hard clear sheet of resin with ultravac pressure adapter.
Fabrication of Splint
The patient is instructed how to proper seat the appliance and the final seating is done by biting.
Patient is instructed to wear it as per disorder like in night for bruxism and in day time for disc problems.
INSTRUCTIONS
A splint should be checked at least once during the first 10 days after delivery. If adjustments are needed and performed a new visit within 1-2 weeks has to be scheduled.
Patients with TMD should preferably be recalled after 2-6 months. Other splint patients need to be seen 1-2 times per year.
At the recall visit you should consider if the patient may cease using a splint.
Important points in splint management
REFERENCES..
1. Gray’s Anatomy2. Fundamentals of occlusion and TMJ disorders -- Okeson3. Grant’s Atlas of Human Anatomy4. Occlusion – Ash RamfJord5. Functional occlusion by dawson6. Joseph H. Kronman et al (ajodo 1994;105:257-64.)7. Stavros Kiliaridis et al ,European Journal of Orthodontics 25 (2003) 259–263
HUMOR
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