Anatomy of temporomandibular joint

Introduction, Development of TMJ , Part of TMJ, Articular surfaces, Glenoid Fossa, Articular eminence, Condyle, Capsule, Articular disc, Synovial fluid, Ligaments, Blood Supply, Nerve supply, Movements of TMJ, Muscles acting on TMJ, Clinical Anatomy

1. ANATOMY OF TEMPOROMANDIBULAR JOINT PRESENTED BY: DR GAYATRI MEHROTRA

2. INTRODUCTION TMJ is the articulation between the head of the mandible and the mandibular fossa and articular tubercle of the temporal bone.

3. Also known as: Bicondylar joint Ginglymodiarthroidal joint Provides hinging movement in one plane, thus considered as ginglymoid joint Provides for gliding movements,thus considered as arthroidal joint Ginglymodiarthroidal joint

4. It is considered as a synovial joint of the condylar variety. It is classified as a compound joint because it is made up of 3 bones: Anterior part of mandibular fossa and articular tubercle of temporal bone. Head of the mandible. Articular disc ( serves as a nonossified bone ).

5. DEVELOPMENT OF TMJ At approximately 10 weeks the components of future joint become evident in the mesenchyme between the condylar cartilage of mandible and temporal bone Two slitlike joint cavities and an intervening disk make their appearance in this region by 12 weeks. The mesenchyme around the joint begins to form the fibrous joint capsule.

6. Mandibular fossa is flat at birth and there is no articular eminence, this becomes prominent only following the eruption of the deciduous dentition.

7. The developing disc is highly cellular and vascular. All components of the joint mature by 14 th week of gestation. The fetal disc contains nerve fibres and blood vessels in its periphery. They disappear from the disc proper but remain at the disc attachment after birth.

8. PARTS OF TMJ Articular Surfaces Glenoid Fossa Articular Eminence Articular Disc Capsule Condyle Ligaments

9. ARTICULAR SURFACES Upper articular surface is formed by : Articular eminence Anterior part of mandibular fossa The inferior articular surface is formed by the head of mandible.

10. GLENOID FOSSA The glenoid or mandibular fossa is the concave depression on the inferior surface of the petrous part of the temporal bone. It is bounded posteriorly by the petrotympanic fissure and anteriorly by the articular eminence.

11. ARTICULAR EMINENCE It is present anterior to the glenoid fossa. It is covered by dense,compact,fibrous tissue The fibrous covering is thickest at the descending slope of the eminence. Underlying the fibrous tissue covering is chondroid bone and then compact bone.

12. CONDYLE The adult condyle is elliptical in shape with mediolateral width more than anteroposterior width. mediolateral width= 15-20mm anteroposterior width= 8-10mm The components of the condylar covering vary with age and with the region of the condyle. In the centre of the condyle, cartilage develops and works as secondary cartilage.

13. The cartilage contributes to enlargement of condyle in adulthood as part of adaptive changes in response to overloading. The condyle is vascular at birth and vessels anastomose over the articular surface, but these disappear by the age of 3 yrs.

14. CAPSULE The joint is surrounded by a capsule which is attached beyond the limits of the articular surface. The capsule attaches inferiorly to the priosteum of the neck of the condyle. Lateral aspect attaches to the zygomatic tubercle, lateral rim of glenoid fossa and postglenoid tubercle.

15. Medially, the capsule attaches to the medial rim of the glenoid fossa. The articular surface of condyle is covered by fibrocartilaginous tissue and not hyaline cartilage. Spine of sphenoid Spenomandibular ligament Middle meningeal artery Closely related to the medial capsule

16. ARTICULAR DISC The articular disc is composed of dense fibrous connective tissue , devoid of blood veesels or nerve fibers. In sagittal plane,it can be divided into three regions: Intermediate zone Anterior band Posterior band

17. The disc is thinnest in its center and thickens to form anterior and posterior bands.

18. During movements the disc is somewhat flexible and can adapt to the functional demands of the articular surfaces. The disc maintains its morphology unless destructive forces or structural changes occur in the joint . If these changes occur, the morphology of disc can be irreversibly altered, producing biomechanical changes during function.

19. The articular disc is attached posteriorly to a region of loose connective tissue that is highly vascularized and innervated known as retrodiscal tissue or posterior attachment. Superior Retrodiscal Lamina Inferior Retrodiscal Lamina

20. Articular disc Retrodiscal lamina Posterior attachment

21. Superior lamina Inferior lamina Origin Arises from the posterior band of the disc Arises from the posterior band of the disc Insertion It inserts to the squamotympanic fissure and tympanic part of the temporal bone Inserts into the inferior margin of the posterior articular slope of the condyle Composition Consists primarily of elastic fibers Consist mainly of collagen fibers

22. The disc and its attachment divide the joint into upper and lower compartment. Upper Compartment Passive Volume Of Synovial Fluid=1.2ml Roof Is The Mandibular Fossa Floor Is The Superior Surface Of The Disc

23. Lower Compartment Passive Volume Of Synovial Fluid = 0.9ml Roof Is Inferior Surface Of Disc Floor Is The Articulating Surface Of Mandibular Condyle

24. SYNOVIAL FLUID Joint cavity is filled with synovial fluid, thus TMJ is referred to as synovial joint. Synovial fluid is a filtrate of plasma with added mucins and proteins. Its main constituent is hyaluronic acid.

25. Functions Of Synovial Fluid: Act as a medium for providing metabolic requirement since the articular surfaces are nonvascular. Also serves as a lubricant between articular surfaces during function, thus helps to minimize friction.

26. Joint lubrication is achieved by 2 mechanisms: Boundary Lubrication Weeping Lubrication Moving joint Synovial fluid forced from one area to other of cavity Boundary lubrication comes into action Prevents friction in moving joint

27. During funtion of a joint Forces are created between articular forces Synovial fluid is released Weeping lubrication comes into action Helps eliminate friction in compressed joint

28. HISTOLOGY OF ARTICULAR SURFACES The articular surfaces of the mandibular condyle and fossa are composed of 4 distinct layers or zones: Articular Proliferative Fibrocartilaginous Calcified cartilage

29. LIGAMENTS The ligaments of the joint are made up of collagenous connective tissues. If extensive forces are applied the ligament can be elongated altering the joint function. 3 functional ligaments: The collateral ligament The capsular ligament The temporomandibular ligament(lateral ligament)

30. There are also two accessory ligaments: 1) The sphenomandibular ligament 2) The stylomandibular ligament

31. The Collateral Ligament: These ligaments attach the medial and lateral borders of the articular disc to the poles of the condyle Commonly called discal ligaments 1) medial discal ligament 2) lateral discal ligament

32. Collateral ligaments are true ligaments and do not stretch. They are responsible for the hinging movement of the tmj . The Capsular Ligament: The entire TMJ is surrounded and encompassed by the capsular ligament. Superiorly, it is attached to margins of Articular disc and Articular fossa.

33. Inferiorly, it is attached to the neck of the condyle. A significant function of the capsular ligament is to encompass the joint, thus retaining the synovial fluid.

34. The Temporomandibular Ligament Or Lateral Ligament: The lateral aspect of the capsular ligament is reinforced by strong,tight fibers that make up TM ligament. IHP = Inner Horizontal Portion OOP= Outer Oblique Portion

35. Attached above to the tubercle of the root of the zygoma . Below to the lateral surface and posterior border of the neck of mandible.

36. Force is applied to mandible Inner horizontal portion of ligament becomes tight Prevents the condyle from moving into posterior region of mandibular fossa Thus, protects the retrodiscal tissues from trauma Also, protects lateral pterygoid muscle from over-lengthening or extension

37. The Sphenomandibular Ligament: It is one of the accessory ligament. Attached above to the spine of sphenoid. Below to the lingula of the mandible.

38. The Stylomandibular Ligament: It is the thickened part of the deep part of the capsule of the parotid gland derived from deep cervical fascia. Attached above to the styloid process of temporal bone. Below to the angle of mandible and adjacent part of the posterior part of the ramus of mandible.

39. It limits the excessive protrusive movements of the mandible.

40. RELATIONS OF TMJ

41. BLOOD SUPPLY TMJ is richly supplied by a variety of vessels that surround it. Includes following: Superficial Temporal Artery from posterior Middle Meningeal Artery from anterior 3) Internal Maxillary Artery from inferior

42. Other important arteries are: D eep auricular artery Anterior tympanic artery A scending pharyngeal artery Condyle receives its vascular supply through its marrow spaces by way of inferior alveolar artery and “feeder vessels” that enter directly into condylar head.

43. NERVE SUPPLY TMJ is innervated by the Trigeminal Nerve that provides sensory and motor innervation to muscles that control it. B ranches of mandibular nerve Auriculotemporal nerve Deep temporal nerve Masseteric nerves

44. MOVEMENTS OF TMJ Protraction of mandible: The articular disc glides forward over the upper articular surface, the head of the mandible moving with it. Retraction of mandible: Reversal of protraction.

45. Depression of mandible: The head of mandible moves on the undersurface of the disc like a hinge. In wide opening, this hinge like movement is followed by gliding of the disc and the head of mandible. Elevation of mandible: The movements are reversed in this as they were in depression of mandible.

46. Side to side movements: Head of one side glides forward along with the disc as in protraction, but the head of other side rotates on a vertical axis.

47. MUSCLES ACTING ON TMJ Depression : Lateral pterygoid Platysma Mylohyoid Geniohyoid Anterior belly of digastric

48. Elevation: Temporalis Masseter Medial pterygoid Protraction: Medial pterygoid Lateral pterygoid Superficial fibres of the masseter

49. Retraction: T emporalis posterior horizontal fibres Masseter deep fibres Side to side: Medial pterygoid Lateral pterygoid

50. CLINICAL ANATOMY Dislocation Of Mandible: During excessive opening of mouth or during a convulsion, the head of the mandible of one or more sides may slip anteriorly into the infratemporal fossa, as a result of which there is inability to close the mouth. Reduction is done by depressing the jaw with the thumbs placed on the last molar, and at the same time elevating the chin.

51. Deflection And Deviation Of Mandible: The difference between deviation and deflection is represented by the deviated joint returns to center and the deflected TMJ stays to one side.

52. Derangement Of The Articular Disc: It may result from any injury like overclosure or malocclusion. This give rise to clicking and pain during movements of the jaw.

53. Trismus : It is defined as a prolonged , tetanic spasm of the jaw muscles by which normal opening of the mouth is restricted (locked jaw). Causes : Infection Trauma Tetany Tetanus Neurological disorders Drug induced

54. Ankylosis : Ankylosis means abnormal immobility of a joint. Causes: Trauma Infection Autoimmunedisease Long standing immobilization

55. Jaw Jerk Reflex And Jaw Opening Reflex:

56. In Operations On The Joint , the seventh cranial nerve that is facial nerve should be preserved with care.

57. REFERENCES Management Of Temporomandibular Disorders And Occlusion- 5 Edition- By Jeffrey P. Okeson B D Chaurasia Human Anatomy- 4 Edition- Vol3 Principles Of Anatomy And Oral Anatomy- By M.E.Alkinson And F.H.White Human Anatomy For Dental Students-2 Edition By M V Ramasay Burkets Oral Medicine-11 Edition-by Greenberg And Glick And Ship

58. Textbook Of Oral And Maxillofacial Surgery-by S M Balaji Textbook Of Oral And Maxillofacial Surgery- 2 Edition- Neelima Anil Malik

59. QUESTIONS Ligaments of tmj ? Movements of tmj ? Tmj capsule is formed by? Muscle acting on Tmj ?

60. Various projections for imaging tmj ? Other names for tmj ? Nerve supply for tmj ?