temporomandibular joint anatomy and its prosthodontic implications

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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