temporomandibular joint

TEMPOROMANDIBULAR JOINT

Presented by:

Dr Divya Gaur

CONTENTS

• INTRODUCTION

• ANATOMY

• EMBRYOLOGY

• HISTOLOGY

• AGE CHANGES IN TMJ

• TMJ DISORDERS IN CHILDREN

• TMJ IMAGING

• REFERENCES

INTRODUCTION

• The name is derived from the two bones that form the joint:

– Upper TEMPORAL bone.

– Lower MANDIBLE

• It is a ginglymoarthrodial joint, a term that is derived from ginglymus, meaning a hinge joint, allowing motion only backward and forward in one plane, and arthrodia, meaning a joint of which permits a gliding motion of the surfaces.1 It refers to its dual compartment structure and function.

• The right and left TMJ form a bicondylar articulation and ellipsoid variety of the synovial joints similar to knee articulation.2

ANATOMY

• Articular surface• Mandibular component

• Cranial component

• Articular disc

• Articular capsule

• Ligaments

• Neurovascular components

X Alomar et al. Anatomy of Temporomandibular joint. J Sult 2007; 170-183.

MANDIBULAR COMPONENT

• Ovoid condylar process seated atop a narrow mandibular neck.

• 15 to 20 mm side to side.

• 8 to 10mm from front to back.

• Articular surface is covered with white fibro-cartilage.

• If long axes of both condyles are extended medially, they would meet at approx the basion on the anterior limit of foramen magnum, forming an angle that opens towards the front ranging from 145-160o.


MANDIBULAR COMPONENT (Contd)

• Lateral pole of condyle: rough, bluntly pointed and projects only moderately from the plane of ramus.

• Medial pole: extends sharply inward from this plane.

• Articular surface lies on its anterosuperior aspect.


• Formed by the following parts:

– Articular eminence

– Articular tubercle

– Preglenoid plane

– Posterior articular ridge and postglenoid process

– Lateral border of mandibular fossa

– Entoglenoid process

CRANIAL COMPONENT


• Articular eminence:

– The transverse bony bar that formsthe anterior root of zygoma.

– Most heavily travelled by the condyleand articular disc as they rideforward and backward in normal jawfunction.

• Articular tubercle:

– Small, raised, rough bony knob onthe outer end of articular eminence.

– Serves to attach lateral collateralligament of the joint.

• Preglenoid plane:

– Slightly hollowed, almost horizontal,articular surface continuing anteriorlyfrom the height of articulareminence.

CRANIAL COMPONENT (Contd)


CRANIAL COMPONENT (Contd)

•Posterior articular ridge and postglenoidprocess:

•Posterior part of mandibular fossa is an anteriormargin of petrosquamous suture and is elevatedto form a ridge known as post art ridge or lip.•The ridge increases in height laterally to form athickened cone-shaped prominenc called post-glenoid process.

•Lateral body of mandibular fossa:•Usually raised to form a slight crest joining thearticular turbercle, in front, with post glenoidprocess behind.

•Entoglenoid process:•The fossa narrows on medial side and isbounded by a bony wall.•It passes slightly medially as the medial glenoid

plane.


ARTICULAR DISC

• Most important anatomic structure of the TMJ.

• STRUCTURE: A biconcave fibrocartilaginousstructure located between the mandibularcondyle and the temporal bone component ofthe joint. Roughly oval, firm, fibrous plate withits long axis being tranversely directed.

• SHAPE: Shaped like a peaked cap thatdivides the joint into a larger upper compartmentand a smaller lower compartment.

• SURFACES: Superior surface of the disk issaid to be saddle-shaped to fit into the cranialcontour. Inferior surface is concave to fit againstthe mandibular condyle.

• PARTS: Is thick, round to oval all aroundits rim, divided into an anterior band of 2 mm inthickness, a posterior band 3 mm thick, and thinin the centre intermediate band of 1 mmthickness. More posteriorly there is a bilaminaror retrodiskal region.2


• ATTACHMENT:

– Attached all around the joint capsule except for the strong straps that fix the disk directly to the medial and lateral condylar poles, which ensure that the disk and condyle move together in protraction and retraction.2

– Anterior extension of the disk is attached to a fibrous capsule superiorly and inferiorly.

– In between it gives insertion to the lateral pterygoid muscle.

• FIBRES:– Anterior and posterior bands have transversally running fibres.

– Thin intermediate zone has anteroposteriorly oriented fibres

– Posteriorly, bilaminar region consists of 2 layers

of fibres separated by loose connective tissue.

– Upper layer: temporal lamina is composed of

elastin and is attached to the postglenoid process.

– Inferior layer: inferior lamina curves down behind

the condyle to fuse with the capsule and back of

the condylar neck.

• FUNCTIONS:

– Accommodates a hinging as well as gliding actions between the temporal and mandibular articular surfaces.

– Temporal lamina prevents slipping of the disk while yawning.

– Inferior lamina prevents excessive rotation of the disk over the condyle.

• HISTOLOGY:

– De Bont et al observed in adults, particularly in humans (ages ranging from 58 to 73 years), that the articular surface of the disc was composed of closely packed collagen fibrils running predominantly anteroposteriorly.

ARTICULAR CAPSULE

• A thin sleeve of tissue completely surrounding the joint.

• Extends from the circumference of the cranial articular surface to the neck of the mandible.

• ATTACHMENTS:3

– ANTEROLATERALLY: Articular tubercle

– LATERALLY: Lateral rim of mandibular fossa.

– POSTEROLATERALLY: Postglenoid process

– POSTERIORLY: Posterior articular ridge

– MEDIALLY: Medial margin of temporal bone at its suture with greater wing of sphenoid.

– ANTERIORLY: Preglenoid plane

• RELATIONS:

– LATERALLY AND MEDIALLY: Capsule blends with condylodiscal ligaments.

– MORE LATERALLY: Temporomandibular ligament

– ANTERIORLY: Capsule has an orifice through which lateral pterygoidtendon passes.

A site of possible herniation of intra-articular tissues.4

• Synovial membrane:

– Covers all intra-articular surfaces except the pressure bearing fibro-cartilage.

ARTICULAR CAPSULE (contd)

TEMPOROMANDIBULAR LIGAMENTS

COMPLEX

TEMPOROMANDIBULAR LIGAMENT:

• Designed in two layers.

• Wide outer or superficial layer:

– Fan shaped.

– Origin: Outer surface of articulartubercle and most of the posterior part of zygomatic arch.

– Fibres: run obliquely downward and backward.

– Insertion: Behind and below the mandibular neck.

• Narrow, inner or deep layer:

– Arises from the crest of articulartubercle.

– Runs back as flap strap to the lateral pole of condyle.

SPHENOMANDIBULAR LIGAMENT:

• Origin: Angular spine of sphenoid.

• Fibres: Downward and outward

• Insertion: Lingula of the mandible.

• Relations:

– Laterally: Lateral pterygoid muscle

– Medially: Medial pterygoid muscle, chordatympani nerve, wall of pharynx and pharyngeal vessels.

– Anteriorly: Maxillary artery

– Posteriorly: Auriculotemporal nerve

– Inferiorly: Inferiorly alveolar nerve and vessels.

• Pierced by: Mylelohoid nerve and vessels

• Function: Passive during jaw movements, maintaining same degree of tension during opening and closing of the mouth.

TEMPOROMANDIBULAR LIGAMENTS

COMPLEX (contd)

STYLOMANDIBULAR LIGAMENT:

• Specialized dense, local concentration of deep cervical fascia.

• Origin: Apex and anterior aspect of Stylohyoidprocess and stylohyoid ligament.

• Insertion: Angle and posteror border of mandible.

• Then extends forward as a broad fascial layer covering the inner surface of medial pterygoidmuscle.

• Functions:

– Lax when jaws are closed.

– Slackens noticeably when mouth is opened.

– Tense only in extreme protrusive movements.

TEMPOROMANDIBULAR

LIGAMENTS COMPLEX (contd)

NEUROVASCULAR COMPONENTS

• SENSORY INNERVATION:

– Auriculotemporal and Massetric branches of Mandibular branch of Trigeminal nerve (V cranial nerve).

• PROPRIOCEPTION: involves 4 receptors

– Ruffini endings: static mechanoreceptors which position the mandible.

– Pacinian corpuscles: dynamic mechanoreceptors which accelerate movement during reflexes.

– Golgi tendon organ: static mechanoreceptors for the protection of ligaments around the temporomandibular joint.

– Free nerve endings: pain receptors for the protection of temporomandibular joint itself.

• ARTERIAL BLOOD SUPPLY:

– Branches of external carotid artery, predominantly the Superficial temporal branch.

– Other branches: Deep auricular artery, Anterior tympanic artery, Ascending pharyngeal artery and maxillary artery.

Neither innervation nor vascularization within central portion of articular disc.

EMBRYOLOGY OF TMJ

• Early TMJ structures emerged from a block of embryonic mesenchymal cells interposed between the developing temporal bone and mandible.

• Merida-Velasco et al confirm that the critical period of morphogenesis of TMJ occurs between 7th and 11th week of gestation.

• PRIMARY JOINT:

– At about 7th week, Meckels cartilage extends from the midline backward and dorsally, acting as a scaffold to the developing mandible.

– It terminates at malleus and articulates with the incal cartilage forming the primary joint.

– Factors promoting joint formation are intrinsic and genetically determined.

– This exists for about 4 months until the cartilages ossify and become incorporated in the middle ear.

• SECONDARY JOINT:

– At 3 months of gestation, two distinct regions of mesenchymalcondensation appear:

• TEMPORAL BLASTEMATA

• CONDYLAR BLASTEMATA

TEMPORAL BLASTEMA:

• Give rise to articular eminence and glenoid fossa.

• First appearance of articular fossa occurs at approx 7-7.5 weeks as a visible condensation of deeper staining stellate cells comprising embryonic mesenchyme.

• Spicules of primary cancellous bone appear most prominently at 10-11 weeks.

• Upto 9 weeks, shape of articular fossa is convex.

• Later, the fossa progressively takes on its definitive concave shape.

CONDYLAR BLASTEMA:

• Condensation and shaping of mandibular condyle occur at about the same time as for the articular fossa.

• This mass is superiorly convex.

• Condylar cartilage cells appear at 9-10 weeks.

• Till 10th week, articular fossa and condyle ossify at the same rate. Later articular fossa ossifes faster.

• Small coalesing clefts for the lower compartment of joint cavity appear at about 10 weeks, and for upper compartment at 11.5 weeks.

EMBRYOLOGY OF TMJ

CONDYLAR BLASTEMA (contd)

• These small clefts gradually enlarge and coalesce into larger spaces.

PHASES IN DEVELOPMENT OF TMJ

STAGES EVENTS

Blastematic stage (7-8weeks)

Corresponds with the onset of the organization of condyle and the articulardisc and capsule. During week 8, intramembranous ossification of temporal squamous bone begins.

Cavitation stage (9-11 weeks)

Corresponding to the initial formation of inferior joint cavity (week 9) and the start condylar chondrogenesis. Week 11 marks the initiation of organization of superior joint cavity.

Maturation stage After week 12 of development.

AGE CHANGES IN TMJ

ARTICULAR LAYER:

• Vascular at birth and becomes progressively fibrous.

ARTICULAR DISC:

• Initially flat and highly vascular.

• With ageing, there is marked decrease in vascular supply, the disk becomes fibrous.

• Central part thins with anterior and posterior parts becoming thicker.

• Collagen fibres become coarse and dense and get arranged in a three-dimensional network.

After 20 yrs, superior and anterior part of condyle and posteroinferior part of eminence retain the condylar cartilage.

Reasoning for this: adaptation to functional stress.

HISTOLOGY

CONDYLE:

• Cancellous bone covered by a thin layer of compact bone.

• Trabaculae radiate from the neck of mandible and rach the cortex at right angles, giving maximal strength to the condyle.

• As age progresses, trabaculae thickens, decreasing the size of large marrow spaces.

• Red marrow is of myeloid or cellular type which is replaced by fatty marrow in older individuals.

ROOF OF GLENOID FOSSA:

• Thin compact layer of bone.

• Articular eminence is composed of spongy bone covered with a thin layer of compact bone.

• Areas of chondroid bone are commonly seen in articular eminence.

ARTICULAR SURFACES OF MANDIBULAR CONDYLE AND FOSSA:

• Lined with dense fibrous connective tissue with some elastic fibres.

• Composed of four distinct layers/zones :

– Articular

– Prolferative

– Fibrocartilaginous

– Calcified cartilage

• ARTICULAR ZONE:

– Most superficial layer, found adjacent to the joint cavity.

– Covered with a layer of fibrous tissue.

– Tightly packed collagen bundles oriented parallel to the articular surfaces, allowing them to withstand the forces of movement.

– Adv of fibrous cartilage: less susceptible to the effects of ageing.

• PROLIFERATIVE ZONE:

– Mainly cellular, consisting of undifferentiated mesenchymal cells, that are responsible for the proliferation of articular cartilage in response to functional demands.

HISTOLOGY

• FIBROCARTILAGINOUS ZONE:

– Collagen fibres arranged in bundles in a crossing pattern.

– Provides a 3-dimensional network that provides resistance to compressive and lateral forces.

• CALCIFIED CARTILAGE:

– Fourth and the deepest zone.

– Made up of chondroblasts and chondrocytes distributed throughout the articular cartilage.

– Chondrocytes become hypertrophic and die, causing their cytoplasm to be evacuated, forming bone cells from within the medullary cavity.

HISTOLOGY

ARTICULAR DISC:

• Dense, collagenous fibrous pad between condylar heads and articular surfaces.

• Fibroblasts are elongated and send flat cytoplasmic processes into the interstices between the adjacent bundles.

• Thinnest centrally, and thickens in the periphery.

• Devoid of any blood vessels and nerves , except for extreme periphery which is slightly innervated.

• 80% type I collagen and 5% glycosaminoglycans of its dry weight.

• Of the 5% GAGs, 80% is chondroitin sulphate and 15% is dermatan sulphate.

• Small amount of type III collagen in posterior attachment region.

SYNOVIAL MEMBRANE:

• Lines the inner surface of the joint capsule.

• Folds to form synovial villi which project into the spaces.

• Made up of an intimal layer of synovial cells from 1-4 cells in depth resting over loosely organized subintimal connective tissue layer.

• Connective tissue layer has extensive plexus of nerves and vessels and numerous fibroblasts, mast cells and macrophages.

HISTOLOGY

• Synovial layer lacks a distinct basement membrane: rapid diffusion of substances in and out of joint cavities.

• Synovial fluid: dialysate of plasma.

• Types of synovial cells:

– Type A: synthesis and transport of hyaluronodate and are involved in active phagocytosis.

– Type B: synthesis and transport of proteins into the synovial fluid.

• Functions of synovial fluid:

– Lubrication of the joint

– Essential nutrients for chondrocytes within the cartilage matrix.

– Aid in the phagocytosis and elimination of particulate and dissolved substances.

– Provide necessary vehicle for transport and diffusion of substances in and out of joint cavities.

HISTOLOGY


DISORDERS IN CHILDREN

• Children seldom seek treatment for TMDs but dentist’s awareness of early signs and symptoms can facilitate quicker resolution and prevent progression.

• Clinical evaluation is important– owing to difficulty in verbalizing the precise location and nature of orofacial pain.

• EPIDEMIOLOGY:

– The skewed age and gender distribution suggest a hormonal influence.

– Treatment seeking peaks occur during reproductive years.

– Prevalence of signs and symptoms of TMDs in children varies considerably, due to difference in:

• Population investigated

• By examination methods

• Diagnostic criteria used

• Interindividual and intraindividual variations of examiners.

A study of 3428 consecutive patients of all ages enrolled in a health maintenanceorganization who sought treatment for TMDs revealed that 85.4% were female.5



Wahlund and colleagues reported that the prevalence of TMD in children and adolescents (12-18 yrs) was 7%.6

Nilsson found that prevalence of TMD pain in 28899 youths aged 12-19 yrs was 4.2% and was significantly higher in girls (6%) than in boys (2.7%).

ETIOLOGY:• Historically, malocclusion has been considered a primary cause. • However, the occurrence of malocclusion, occlusal interferences and missing teeth is nearly equal for males and females. 7

• Predisposing factors:•Systemic (affecting the entire body or a particular body system.)•Psychosocial (interaction of psychological and social variables.)•Physiologic (cellular and metabolic processes, neuromuscular.)•Structural (dental occlusion, musculoskeletal, articular, developmental anomalies).

•Precipitating/initiating factors: 7,8

•Trauma or overuse. •Repetitive activities with jaw in sustained or abnormal posture: playing wind instrument or violin or sleep posture.

• Prepetuating/ sustaining factors:9

– Parafunction

– Overuse

– Systemic diseases

– Occlusal factors

– Psychological distress



EXAMINATION FOR TMDs

• RANGE OF MOTION: ROM

– Simple and objective method.

– Mandibular ROM is directly related to height.

– The ability of a patient to place 3 fingers vertically in a handshake position between the incisor teeth (the 3 finger test) approximates a normal range of mandibular opening of 35-50mm.10

– If it is not possible to get even 2 fingers, then the reason for the limited opening should be investigated.

– Excursive mandibular movement to each side is normally 8 to 10 mm.

– Width of a permanent maxillary central incisor is 8to 9 mm, so if a patient can move the lower jaw sideways by the width of upper central incisor, this should be considered normal.

– Pain, mandibular deviation, end-point deflection, catching, or locking associated with these movements should be noted.

• PROVOCATION OF MASTICATORY MUSCLE PAIN:

– Firm bilateral pressure applied to temporalis and masseter muscles while the patient is clenching will reveal tenderness and determine if there is atrophy or hypertrophy, which may be associated with extreme bruxism.

• TMJ PALPATION AND LOAD TESTING:

– Lateral aspect of the capsule is examined by having the patient open their mouth halfway while the clinician firmly presses the index fingers in the depression created behind each condyle, just in front of the tragus of the ear.

– Presence of discomfort is noted as the patient slowly opens and closes.

– Joint loading is accomplished by the clinician applying force under the angle of the mandible, with the teeth slightly out of contact.

– Functional loading while chewing on a cotton roll or wax between the last molars provides information about contralateral capsular pain. This squeezing action torques the TMJ on the opposite side and can trigger the clicking or muscle pain that the patient experiences while chewing.

– Biting on tongue blade on the side of pain may reduce the pain if it is related to inflammation.


• DIFFERENTIATION OF TMJ SOUNDS:

– TMJ sounds can be categorized as:

• Clicking

• Soft tissue crepitus

• Hard-tissue grating

– A stethoscope applied lightly over the joint is helpful in distinguishing the character and intensity of sounds.

– The noise should be evaluated on opening, closing and in excursive jaw movements.

– Applying upward pressure at the angle of mandible usually increases the intensity of the sounds and this should be done if the patient reports a recent history of sounds but none were detected in unloaded jaw movements.


TMJ IMAGING

• Recommended when there is a recent history of mandibular trauma, evidence of developing facial asymmetry or when hard tissue grinding or crepitus is detected.

• Age-related changes of mandibular condyle should be considered:

– As size of condyles increase, the angle decreases and therefore the position of condyle within the fossa changes.

– The shape of mandibular condyle changes from a round to oval configuration.

• Most commonly accomplished with a panoramic view.

– Low cost

– Widespread availability

– Minimal radiation

– Reliable for evaluating condylar head morphology and angulation and cortex density but do not permit evaluation of joint space or condylarmotion.

– Useful for measuring vertical ramus height, which ahs been shown to be reduced in growing children with disc displacement.11

– A steeper mandibular plane angle, increased antegonial notching and skeletal facial asymmetry are seen more often in patients with TMD. 12

• Computed tomography (CT) or cone beam computed tomography (CBCT) is indicated for detection of TMJ osseus abnormalities, fracture detection and analusis of facial asymmetry.

• Magnetic resonance imaging produces no ionizing radiation and provides visualization of position and contours of the TMJ disc and other soft tissues, can detect inflammation.

TMJ IMAGING

REFERENCES

1. Dorland WA: medical dictionary. Philadelphia and london, saunders co.,1957.

2. Williams pl: gray’s anatomy, in skeletal system (ed38). Churchill livingstone london 1999, pp578-582.

3. Patnaik vvg, bala s,singla rajan k: anatomy of temporomandibular joint? A review. J anatsoc india 49(2):191-197, 2000

4. Kreutziger KL, mahan PE: temporomandibular degenerative joint disease. Part II. Diagnostic procedure and comprehensive management. Oral surg oral med oral pathol40(3):297-319, 1975

5. Howard JA. Tempo mand joint disorders, facial pain and dental problems in performing artists. In: sataloff RT, brandfonbrener AG, lederman RJ, editors. Performing arts medicine. 3rd edition. Naberth (PA): science and medicine 2010.P151-96.

6. Mohlin b, axelsson s, paulin g et al. Tmd in relation to malocclusion and orthodontic treatment. Angle orthod 2007;77(3):542-8.

7. Howard ja, lovrovich at. Wind instruments: their interplay with orofacial structures. Med probl perform art 1989;4:59-72

8. Kovero o, konone m. Signs and symptoms of tmds and radiologically observed abnormalities in the condyles of tmj of professional violin and viola players. Acta odontolscand 1995;53(2):81-4

9. Rugh jd, woods bj, dahlstrom l. Temporomandibular disorders : assessment of psychological factors. Adv dent res 1993;7(2):127-36

10. Abou-atme ys, chedid n, melis m et al. Clinical measurement of normal maximum mouth opening in children. Cranio 2008;26(3):191-6

11. Nebbe b, major pw, prasad n. Female adolescent facial pattern associated with tmj disk displacement and reductin in disk length: part 1. Am J orthod dentofacial orthop1999;116(2):168-76.

12. Dibbets jm, carlson ds. Implications of tm disorders for facial growth and orthodontic treatment. Semin orthod 1995;1(4):258-72.


Part II

Dr Divya Gaur

I yr PG

Dept of Pedodontics and Preventive Dentistry

CONTENTS

• APPLIED ANATOMY

• TMJ MOVEMENTS

• TMJ DISORDERS

• REFERENCES

TMJ MOVEMENTS

temporomandibular joint

Health & Medicine

articular eminenceenp

articular tubercleco

articular turbercle

height of articular

ginglymoarthrodial joint

hinge joint

j sult

condylar process x alomar