Journal of Advanced Clinical and Research Insights

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Temporomandibular joint - An anatomical view
  JCRI
REVIEW ARTICLE
Temporomandibular joint - An anatomical view
Sushant A. Pai, Shruti R. Poojari, Keerthi Ramachandra, R.K.V. Patel, Mangala Jyothi
Department of Prosthodontics Including Crown and Bridge, Sri Rajiv Gandhi College of Dental Science and Hospital, Bengaluru, Karnataka, India
Correspondence: Dr. Shruti R. Poojari, Department of Prosthodontics Including Crown and Bridge, Sri Rajiv Gandhi College of Dental Science and Hospital, Cholanagar, Hebbal, Bengaluru, Karnataka, India.
E-mail: shrutipoojari40@gmail.com
Received: 11 December 2018
Accepted: 21 January 2019
doi: 10.15713/ins.jcri.247
 
ABSTRACT
Temporomandibular joint (TMJ) is one of the most intricate and complicated loading joints found in humans. TMJ is also called the mandibular joint; it is an ellipsoid variety of the left and right synovial joints which form a bicondylar articulation. The components of this joint are a fibrous capsule, a disk, synovial membrane, fluid, and tough adjacent ligaments. The mandible and the cranium are mechanically two different components; therefore, the appropriate term for this joint is the craniomandibular articulation. It is not possible to understand the accurate points of occlusion without a thorough knowledge of the biomechanics, physiology, and anatomy of TMJ. The primary necessity for successful occlusal treatment is steady and comfortable TMJ. This understanding of the TMJ is the foundation to diagnosis and treatment of almost everything a dentist does.
Keywords: Temporomandibular joint, temporomandibular joint anatomy, temporomandibular joint biomechanics
How to cite this article: Pai SA, Poojari SR, Ramachandra K,Patel RKV, Jyothi M. Temporomandibular joint - An anatomicalview. J Adv Clin Res Insights 2019;6:1-5.
 
 

Introduction

The part where the articulation of the temporal bone of the cranium and the mandible occurs is called the temporomandibular joint (TMJ), definitely one of the intricate joints in the body.[1] The articular disk is fibrous tissue that is present between the TMJ and acts as a buffer.[2]Mastication and speech are the main functions of the TMJ and are of at most interest to dentists, clinicians, and radiologists.[1] TMJ provides hinging movement in one plane, thereforeknown as ginglymoid joint and at the same time it provides glidingmovements, which is known as arthrodial joint; therefore, it is known as ginglymoarthrodial joint [Figure 1].[3]

Pecularity of TMJ
  • Bilateral diarthrosis.
  • Only joint in the human body that has a rigid end point due to closure of the teeth making occlusal contact.[3]
  • The surface that articulates is covered by fibrous cartilage instead of hyaline cartilage.[4]
  • Compared to other diarthrodial joints, TMJ develops the last (7th week indexed universal life [IUL]).[5]
  • TMJ is formed from distinct blastema.[5]

 
Development of TMJ

It develops from first pharyngeal arch, innervated by fifth cranial nerve, and develops from mesenchyme between the temporal and condylar blastemas.[6]
  • 7th-8th weeks IUL - By this time the primary cancellous bone is first seen in the temporal mesenchyme and by 8th week it is seen in ramal mesenchyme.
  • 9th-week IUL - The rudimentary mandible is formed by intramembranous ossification.
  • 10th-week IUL - The condylar cartilage is first seen.[5]
  • First sign of lower TMJ space is seen when a cleft is formed between the condylar process and the temporal component [Figure 2].[5]
  • 11th- 12th-week IUL - Another cleft forms the upper TMJ space [Figure 3].[5]
  • TMJ disk is formed by condensation of the mesenchyme between the lower and upper TMJ spaces.
  • 12th week - The disk is connected to the upper part of the lateral pterygoid. The condylar process is attached to the lower part of the lateral pterygoid.
  • 14th week - Lower and upper TMJ spaces are fully formed. Meckel's cartilage plays no part in the development of TMJ.[7]
    TMJ disk develops separately from the tendon of the external pterygoid muscle.[8]

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Pai, et al. Temporomandibular joint - An anatomical view

Temporomandibular joint - An anatomical view
Figure 1: Introduction

Temporomandibular joint - An anatomical view
Figure 2: First sign of lower temporomandibular joint space isseen when a cleft is formed between the condylar process and thetemporal component

Temporomandibular joint - An anatomical view
Figure 3: Another cleft forms the upper temporomandibular jointspace

Components[9]

1. Bony components
  • Glenoid fossa.
  • Mandibular condyle
  • Articular eminence

 
2. Ligaments
A. Primary
  • Fibrous capsule
  • Lateral ligament
  • Collateral ligament

B. Accessory
  • Sphenomandibular ligament
  • Stylomandibular ligament

3. Articular disk
4. Muscles.

Bony Components

Glenoid/mandibular/articular fossae

It is an elliptical concave depression, made up of squamousportion of temporal bone. They are bordered, in front, by thearticular tubercles; behind they are separated from the externalacoustic meatus by tympanic part of the bone. Posterior roof ofthe mandibular fossa is very thin and, therefore, cannot sustainheavy forces.[10]

Mandibular condyle

This component has a tapered mandibular neck with anovoid condylar process on it. It is 16-20 mm side to side and9-10 mm from back to front.[1] There is upward projection fromthe posterosuperior part of the ramus, wherein upper end isexpanded from side to side to form the head. The head is coveredwith fibrocartilage and articulates with temporal bone. From thefront view, there are lateral and medial projections known as poles.The lateral pole is less prominent compared to medial pole.[3]

Articular eminence

A convex bony prominence is present immediately anterior tothe fossa known as articular eminence. The degree of convexityof the articular eminence is important, as the steepness of thissurface dictates the pathway of the condyle when the mandibleis positioned anteriorly, but it is also highly variable. It has athick dense bone and can to tolerate heavy force unlike glenoidfossa.[3,9]

Articular disck

The articular disk is one of the significant anatomic structures ofthe TMJ. It is located between the temporal bone and mandibularcondyle; it is a biconcave fibrocartilaginous structure. It rotateson the condyle like a handle of a bucket which is attached tolateral and medial poles of the condyle. It helps the gliding andhinging actions between the mandibular articular and temporalbone.[2] The disk is firm, fibrous, and nearly oval plate with itslong axis being transversely directed. It looks like a peaked capthat divides the joint into lower and upper compartments. Theupper compartment allows the socket to slide up and down theeminence. The lower compartment serves as a socket, in whichthe condyle rotates. The inferior surface of the disk is concaveto fit in the mandibular condyle, whereas the superior surface issaddle shaped to fit into the cranial contour [Figure 4].

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Temporomandibular joint - An anatomical view Pai, et al.

The disk is oval to round and thick all around its rim; itdivides into an anterior band of 2 mm thick, a posterior band of3 mm in thickness, and an intermediate band of 1 mm thicknesswhich is thin in the center.

Thick anterior band

It continues into the loose fibroelastic connective tissue. It isavascular and innervated. Also known as anterior foot extension.[2]

Thick posterior band

It is attached to the back of the condyle with an inelastic bandof collagen fibers which prevents the disk from rotating too farforward. It is highly vascular and richly innervated. Also knownas pis vasculosa.[2]

The retrodiscal is present in the intra-articular part which isbehind the disk and condyle. When the disk and condyle are in centricrelation, they are seated more anteriorly. As the condyle translatesanteriorly, the volume of retrodiscal tissue increases immediately. It iscompressed and folded in the space of the joint when the jaw closes;once the jaw opens, the condyle moves forward and downward. Theretrodiscal tissue is best seen in the open-mouth position.[2]

Histology of Articular Surfaces

The articular surfaces are made of four different layers or zones.
  • Articular zone - collagen type I fibers aligned parallel to thearticular surface in saggital and transverse directions. Due tothis fibrous connective tissue layer, it is less prone to the effectof breakdown over time and aging.
  • Proliferative zone - Mostly cellular, it has regenerative anddifferentiation activity throughout life.
  • Cartilaginous zone - Collagen type II fibers in randomorientation offer substantial resistance against lateral andcompressive forces, but they become thinner with age.
  • Calcified zone - Deepest zone consists of chondrocytes,chondroblast, and osteoblast. This is the best site forremodeling activity as bone growth takes palce.[3,4]

Ligament

Ligaments have a significant role in protecting the structures.They do not take part actively into function of the joint but act aspassive restrictive devices to hamper border movements.

Primary ligaments (functional ligaments)

Collateral (discal) ligaments

The collateral ligaments join the medial and the lateral marginsof the articular disk to the condylar poles. They are also known asdiscal ligaments, and there are two types: The medial edge of thedisk to the medial pole of the condyle is attached by the medialdiscal ligament and the lateral edge of the disk to the lateralpole of the condyle is attached by the lateral discal ligament.Their role is to restrict the discal movements; they permit thecondyle to move passively with the disk as it glides posteriorlyand anteriorly. They cause the hinging movement of the TMJ,which occurs between the articular disk and the condyle. Thediscal ligaments are innervated and have a vascular supply.Their innervations give an idea regarding joint movement andposition. Pressure on these ligaments causes pain.[3]

 
The fibrous capsular ligament

The whole TMJ is enclosed by the capsular ligament. Superiorto the temporal bone, the fibers of the capsular ligament areattached. Inferiorly, they are attached to the condylar neck.[3]

Temporomandibular/lateral ligament [Figure 5]

The lateral aspect of the capsular ligament is toughened by firmfibers, which forms the lateral ligament or the TM ligament.It has two parts, an inner horizontal portion (IHP) and anouter oblique portion. The outer portion extends from theouter surface of the articular tubercle and zygomatic processposteroinferiorly to the outer surface of the condylar neck. TheIHP extends from the outer surface of the articular tubercle andzygomatic process posteriorly and horizontally to the lateralpole of the condyle and posterior part of the articular disk. Theoblique portion of the TM ligament prevents unnecessary fallingof the condyle, therefore restraining the amount of openingof the mouth. This portion of the ligament also influences thenormal opening movement of the mandible.[3]

Temporomandibular joint - An anatomical view
Figure 4: The articular disk

Temporomandibular joint - An anatomical view
Figure 5: Capsular ligament (lateral view), which extends anteriorlyto include the articular eminence and encompass the entire articularsurface of the joint. Temporomandibular ligament (lateral view), thereare two distinct parts: The outer oblique portion (OOP) and the innerhorizontal portion (IHP). The OOP limits normal rotational openingmovement; the IHP limits posterior movement of the condyle and disk

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Pai, et al. Temporomandibular joint - An anatomical view

Minor ligaments
  • The sphenomandibular ligament
  • The stylomandibular ligament.

Blood Supply
  • Lateral aspect - Superficial temporal artery
  • Deep and posterior aspect of retrodiscal capsule - Deep

auricular, posterior auricular, and masseteric artery. Vascularsupply to the lateral pterygoid muscle also supplies thecondylar head by numerous nutrient foramina vessels
  • Veins
  • Maxillary vein
  • Pterygoid venous plexus.[9]

Nerve Supply
  • Mandibular nerve innervates the TMJ. Three branches fromthis nerve send terminals to the joint capsule.
  • Auriculotemporal nerve a posterior, medial, and lateral partsof the joint.
  • Posterior deep temporal a anterior part of the joint.
  • Masseteric nerve.[9]

Biomechanics of the TMJ

The TMJ is an tremendously intricate joint. The fact that thereare two TMJs connected to the same bone (the mandible)further complicates the function of the entire masticatorysystem. Although each joint can simultaneously carry outdifferent functions, they can never act without influencing theother. A sound understanding of the biomechanics of the TMJis essential and basic to the study of function and dysfunction inthe masticatory system.

The TMJ is a compound joint. Its function and structure canbe divided into two different systems:
  • One joint system comprises the tissues that surroundthe inferior synovial cavity (i.e., the articular disk andthe condyle). Since the disk and the condyle are tightlyattached by the medial and lateral discal ligaments, the onlyphysiologic movement that can take place involving thesesurfaces is a rotation of the disk on the articular surface of thecondyle. The disk and its attachment to the condyle are calledthe condyle-disk complex; this causes rotational movementin the TMJ.

 
  • The second system is when the surface of the mandibularfossa is functioning against the condyle-disk complex. As thedisk and the articular fossa are not firmly attached, free slidingmovement occurs in between superior cavity surfaces. Thisoccurs when the mandible is moved forward (translation).Translation occurs in the superior joint cavity between themandibular fossa and the superior surface of the articular disk.[3]

For the opposite movements of the mandible, differentmuscles are essential. The abductors (jaw openers) and adductors(jaw closers) are muscles of mastication. The temporalis,masseter, and medial pterygoid muscles are adductors, while thelateral pterygoid muscles are the primary abductors of the jaw.The muscles that cause protrusive are also causes alternativelyside to side jaw movements.[1,9]

Lubrication of the joint

There are two sources from where the synovial fluid comes: Firstfrom plasma by dialysis and second by secretion from Type Aand B synoviocytes which is not >0.05 ml. Nevertheless, contrastradiography studies have predicted that the upper compartmenthas the capacity of roughly 1.2 ml of fluid without any pressurecreated, while the lower can hold up to 0.5 ml.[11]

Teeth and occlusion

The mode by which the teeth fit in together may influence the TMJ.Highest support to the joint and the muscle is provided by a steadyocclusion with excellent tooth contact, whereas poor occlusion cancause the muscles to break down and eventually cause impairmentto the joint. Unsteadiness of the occlusion can amplify the force onthe joint, causing destruction and deterioration.[1]

Conclusion

It is not possible to understand the minute points of occlusionwithout a proper knowledge of the biomechanics, anatomy, andphysiology of TMJ. The primary requisite for successful occlusaltreatment is stable TMJ. Only if we have good knowledge ofthe normal and healthy TMJ functions that we will be able toanalyze what is wrong when it isn't functioning comfortably.This knowledge of TMJ is a foundation on which diagnosis andtreatment planning are based.

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  2. Dawson PE. Functional Occlusion from TMJ to Smile Design. StLouis: Elsevier; 2007.
  3. Okeson JP. Management of Temporomandibular Disorders andOcclusion. 7th ed. St Louis: Elsevier; 2013.
  4. Gray R, Al-Ani Z. Temporomandibular Disorders A ProblemBased Approach. 1st ed. New Jersey: Wiley Blackwell; 2011.
  5. Standring S. Gray's Anatomy the Anatomical Basis of ClinicalPractice. 40th ed. New York: Churchill Elsevier; 2008.

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  1. Kumar GS. Orban's Oral Histology and Embryology. 13th ed. StLouis: Elsevier; 2011.
  2. Merida-Velasco JR, Rodriguez-Vazquez JF, Merida-Velasco JA,Sanchez-Montesinos I, Espin-Ferra J, Jimenez-Collado J, et al.Development of the human temporomandibular joint. Anat Rec1999;255:20-33.
  3. Baume LJ, Holz J. Ontogenesis of the human temporomandibularjoint 2. Development of the temporal components. J Dent Res1970;49:864-75.

 
  1. Chaurasia BD. Human Anatomy Head and Neck. 5th ed.New Delhi: CBS Publishers and Distributors; 2010.
  2. Heartwell CM. Syllabus of Complete Dentures. 4th ed.Philadelphia, PA: Lea and Febiger, Publishers; 1992.
  3. Toller PA. Temporomandibular capsular rearrangement. Br JOral Surg 1974;11:207-12.

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