Temporomandibular joint with its anatomy

tmj

1. Temporomandibular joint Presented By- Dr. Kreeti Sargam MDS 2 nd Year Department Of Prosthodontics, Crown, Bridge And Implantology Rishiraj College Of Dental Science And Research Center

2. CONTENT Introduction Growth and development Age changes Functional anatomy Bony changes Soft tissue components Muscles Innervations and blood supply Biomechanics of TMJ Functional movements Mechanism of disc control Border movements Conclusion References

3. Introduction The temporomandibular joint and the associated musculature have been the subject of vast and intensive study for many years. Anatomic dissection, physiologic experiments in nerve and muscle stimulation, comparative observations of healthy, diseased, and malformed organs in the living body, and roentgenographic studies have yielded much valuable information .

4. The TMJ is a complex joint both morphologically and functionally. It is the articulation between the mandible and the cranium. The bony elements of this articulation are the mandibular condyles below and the squamous temporal bones above. An articular disc is interposed between the temporal bone and the mandible, dividing the articular space into upper and lower compartments. Gliding or translatory movements occur primarily in the upper compartment, while the lower compartment functions primarily as a hinge or rotary joint. Therefore, the TMJ is often classified as a hinge joint with a movable socket.

5. The TMJ articulation consists of mandibular or glenoid fossa, an articular eminence or tubercle, a condyle, a separating disk, a joint fibrous capsule an extracapsular ligament.

6. Articulatory system The articulatory system comprises of the following: Temporomandibular joint (TMJ) Masticatory and accessory muscles. Occlusion of the teeth. The occlusion of the teeth plays an important role in the function of the TMJ. Normally, the greatest part of the force of mastication is borne by the dentition of the jaws, but in case of occlusal disharmony, a great deal of force can be shifted to the joint itself.

7. Growth and development There are 3 stages that define the normal embryologic development of the TMJ : Blastemic stage Cavitation stage Maturation stage

8. Acc. To Baume, temporomandibular articulation originate from two different blastema.

9. Temporomandibular joint development stages

10. Growth and development- joint innervations 4 th fetal month- nerve fibers may be observed in the articular capsule. 5 th month- appear to reach the disc. 6 th month- widest distribution over the condyle and within the disc. Nerve fibers in capsule innervate the synovial membrane of the joint as well

11. The growth of face and cranium involves two basic types of growth changes; 1) Displacement 2) Remodeling Both of these process, together constitute the growth mechanism of craniofacial skeleton. As mandibular moves forward and downward, it grows upward and backward at the same time by an equal amount.

12. Age changes of the TMJ CONDYLE- Becomes more flattened. Fibrous capsule becomes thicker. Osteoporosis of underlying bone. Thinning or absence of cartilaginous zone. DISK- Becomes thinner. Shows hyalinization and chondroid changes.

13. SYNOVIAL FOLD- Becomes fibrotic with thick basement membrane. BLOOD VESSELS AND NERVES- Walls of blood vessels thickened. Nerves decrease in number.

14. These age changes lead to: Decrease in the synovial fluid formation. Impairment of motion due to decrease in the disc and capsule extensibility. Decrease the resilience during mastication due to chondroid changes into collagenous elements. Dysfunction in older people.

15. Functional anatomy – BONY COMPONENTS Condylar head Glenoid fossa Articular eminence

16. Mandibular Condyle   This component consists of an ovoid condylar process seated a top a narrow mandibular neck. It is 15 to 20 mm side to side and 8 to 10mm from front to back. Thus, if the long axis 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 lateral pole of the condyle is rough, bluntly pointed, and projects only moderately from the plane of ramus, while the medial pole extends sharply inward from this plane.

17. Glenoid Fossa Glenoid fossa is a large oval hollow, bounded in front by the anterior eminentia articularis and behind by part of the temporal . The petrotympanic fissure divides this fossa into two portions : -the anterior, which articulates with the condyle head of the mandible to form the temporomandibular articulation proper, and -the posterior which is occupied sometimes by a part of the parotid gland. The anterior or mandibular cavity is situated in the inferior surface of the squama of the temporal bone. Its interior surface is formed above by the deepest portion of the fossa, anteriorly by the anterior eminentia articularis, posteriorly by the posterior eminentia articularis (post glenoid process, posterior lip), and medially and laterally by two short lips descending from the medial and lateral boundaries of the fossa.

18. Articular Eminence This is the entire transverse bony bar that forms the anterior root of zygoma. This articular surface is most heavily traveled by the condyle and disk as they ride forward and backward in normal jaw function. B : articular fossa (inferior view). AE, articular eminence; MF, mandibular fossa; STF, squamotympanic fissure.

19. FUNCTIONAL ANATOMY- SOFT TISSUE COMPONENT ARTICULAR DISC SYNOVIAL MEMBRANE LIGAMENTS MUSCLES

20. Articular Disc   The articular disc is a plate of fibrocartilage, oval in shape. It is interposed between the condylar head and the mandibular fossa and is connected with the articular capsule at its circumference. It divides the joint into two cavities, superior and inferior, which are lined up by a synovial membrane that is reflected from the capsular ligament. The lower cavity is the smaller of the two.

21. Divided into 3 bands: Anterior—this thick band lies just anterior to the condyle with the mouth closed Intermediate—this band, the thinnest part, is located along the articular eminence with the mouth closed Posterior—this thick band is located superior to the disc with the mouth closed

22. Additional attachments: Medial/ lateral—strong medial and lateral collateral ligaments anchor the disc to the condyle Anterior—the disc is attached to the capsule and the superior head of the lateral pterygoid, but not the condyle, allowing the disc to rotate over the condyle in an anteroposterior direction Posterior—the disc is continuous with the bilaminar zone that blends with the capsule

23. Bilaminar Zone (Posterior Attachment Complex) A bilaminar structure located posterior to the articular disc Highly distortable, especially on opening the mouth Composed of : Superior lamina (stratum)—contains elastic fibers and anchors the superior aspect of the posterior portion of the disc to the capsule and bone at the post-glenoid tubercle and tympanic plate

24. Retrodiscal pad—the highly vascular and neural portion of the TMJ, made of collagen, elastic fibres, nerves, and blood vessels (a large venous plexus fills with blood when the condyle moves anteriorly) Inferior lamina (stratum)—contains mainly collagen fibers and anchors the inferior aspect of the posterior portion of the disc to the condyles

25. TMJ COMPARTMENTS The articular disc divides the TMJ into superior and inferior compartments The internal surface of both compartments contains specialized endothelial cells that form a synovial lining that produces synovial fluid, making the TMJ a synovial joint. Synovial fluid acts as: A lubricant A medium for providing the metabolic requirements to the articular surfaces of the TMJ

26. Superior compartment Between the squamous portion of the temporal bone and the articular disc Volume = 1.2 mL Provides for the translational movement of the TMJ Inferior compartment Between the articular disc and the condyle Volume = 0.9 mL Provides for the rotational movement of the TMJ (A) TMJ articular space compartments: (1) Articular disk or meniscus, (2) Temporodiskal or superior compartment, (3) Condylodiskal or inferior compartment, (4) Retrodiskal tissue ;

27. Capsule The joint capsule is formed of fibroelastic tissue that surrounds the condylar head; it is attached to the glenoid fossa superiorly and the articular eminence anteriorly. The lateral ligament is a thickening of the capsule that is attached to the condylar neck up to 1 cm from the joint. The TEMPOMANDIBULAR JOINT is innervated by branches from the mandibular division of the trigeminal nerve, mostly through the auriculotemporal branch, together with branches from the masseteric and deep temporal nerves. Postganglionic sympathetic nerves supply the tissues associated with the capsular ligament and the looser posterior bilaminar extension of the disc. The capsule of the TEMPOMANDIBULAR JOINT, lateral ligament and retroarticular tissue contain mechanoreceptors and nociceptors: proprioceptive input from mechanoreceptors helps to control mandibular posture and movement.

28. This disc of fibrocartilage is thinnest at its center and thickest at the circumference. Its inferior surface, where it accommodates the condyle head, is concave. The superior surface is concave anteriorly and convex posteriorly and is in contact with the articular surface of the temporal bone. The disk is thick, round to oval all around its rim, divided into an anterior band of 2 mm in thickness, a posterior band 3 mm thick, and thin in the centre intermediate band of 1 mm thickness. More posteriorly there is a bilaminar or retrodiskal region. The disk is 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. The anterior extension of the disk is attached to a fibrous capsule superiorly and inferiorly. In between it gives insertion to the lateral pterygoid muscle where the fibrous capsule is lacking and the synovial membrane is supported only by loose areolar tissue

29. Synovial membrane and fluid The internal surfaces of the cavities are surrounded by specialized endothelial cells, which form a synovial lining. This lining, along with a specialized synovial fringe located at the anterior border of the retrodiscal tissues, produces synovial fluid, which fills both joint cavities. Thus the TMJ is referred to as a synovial joint .

30. This synovial fluid serves two purposes. Since the articular surfaces of the joint are nonvascular, the synovial fluid acts as a medium for providing metabolic requirements to these tissues. The synovial fluid also serves as a lubricant between articular surfaces during function. The articular surfaces of the disc, condyle, and fossa are very smooth, so that friction during movement is minimized. The synovial fluid helps to minimize this friction further .

31. Lubrication

32. BOUNDARY LUBRICATION Synovial fluid lubricates the articular surfaces by way of two mechanisms. The first is called boundary lubrication, which occurs when the joint is moved and the synovial fluid is forced from one area of the cavity into another. The synovial fluid located in the border or recess areas is forced on the articular surface, thus providing lubrication. Boundary lubrication prevents friction in the moving joint and is the primary mechanism of joint lubrication.

33. WHEEPING LUBRICATION A second lubricating mechanism is called weeping lubrication. This refers to the ability of the articular surfaces to absorb a small amount of synovial fluid. During function of a joint, forces are created between the articular surfaces. These forces drive a small amount of synovial fluid in and out of the articular tissues. Weeping lubrication helps eliminate friction in the compressed but not moving joint. Only a small amount of friction is eliminated as a result of weeping lubrication; therefore prolonged compressive forces to the articular surfaces will exhaust this supply

34. THE TEMPOROMANDIBULAR LIGAMENT Ligaments are made up of collagenous connective tissues fibers that have particular lengths. They do not stretch. Ligaments do not enter actively into joint function but instead act as passive restraining devices to limit and restrict border movements. Three functional ligaments support the TMJ: (1) the collateral ligaments, (2) the capsular ligament, and (3) the temporomandibular ligament (TML).

35. There are also two accessory ligaments: (4) the sphenomandibular and (5) the stylomandibular

36. Collateral Ligaments Composed of 2 ligaments: Medial collateral ligament —connects the medial aspect of the articular disc to the medial pole of the condyle . Lateral collateral ligament —connects the lateral aspect of the articular disc to the lateral pole of the condyle. Frequently called the discal ligaments . Composed of collagenous connective tissue; thus, they are not designed to stretch.

37. Capsular ligament The entire TMJ is surrounded and encompassed by the capsular ligament. The fibers of the capsular ligament are attached superiorly to the temporal bone along the borders of the articular surfaces of the mandibular fossa and articular eminence. Inferiorly, the fibers of the capsular ligament attach to the neck of the condyle.

38. The capsular ligament acts to resist any medial, lateral, or inferior forces that tend to separate or dislocate the articular surfaces. A significant function of the capsular ligament is to encompass the joint, thus retaining the synovial fluid. The capsular ligament is well innervated and provides proprioceptive feedback regarding position and movement of the joint

39. Temporomandibular (Lateral) Ligament The thickened ligament on the lateral aspect of the capsule Prevents posterior displacement of the condyle Composed of 2 separate bands: Outer oblique part—largest portion; attached to the articular tubercle; travels posteroinferiorly to attach immediately inferior to the condyle; this limits the opening of the mandible Inner horizontal part—smaller band attached to the articular tubercle running horizontally to attach to the lateral part of the condyle and disc; this limits posterior movement of the articular disc and the condyle

40. Stylomandibular ligament Composed of a thickening of deep cervical fascia Extends from the styloid process to the posterior margin of the angle and the ramus of the mandible Helps limit anterior protrusion of the mandible

41. Sphenomandibular ligament Remnant of Meckel’s cartilage Extends from the spine of the sphenoid to the lingula of the mandible Some authors suggest it may help act as a pivot on the mandible by maintaining the same amount of tension during both opening and closing of the mouth Some authors suggest it may help limit anterior protrusion of the mandible Is the ligament most frequently damaged in an inferior alveolar nerve block

42. The Muscles Of Mastication The functions of the muscles of mastication in jaw movements are coordinated and balanced by normal muscle tone. Abnormal contraction of any one individual muscle, disrupts the synchronous function that produces coordinated movements. The muscles of mastication (medial and lateral pterygoid, masseter, buccinator, mylohyoid, temporalis and anterior belly of the digastric) are assisted by the suprahyoid and digastric muscles, especially in the jaw opening movements. The tongue with motor innervation accomplished by the hypoglossal nerve, is a strong muscular structure, whose action and position affects jaw movements.

43. The Masseter

44. The Temporalis

45. The Lateral Pterygoid

46. The Medial Pterygoid

47. The Digastric

48. The Arterial Supply

49. Venous Drainage

50. Sensory Innervation

51. Biomechanics of TMJ Functional movements of TMJ Disc control Mandibular movements

52. The TMJ is a compound joint. Its structure and function can be divided into two distinct systems: One joint system comprises the tissues that surround the inferior synovial cavity (i.e., the condyle and the articular disc). Since the disc is tightly bound to the condyle by the lateral and medial discal ligaments, the only physiologic movement that can occur between these surfaces is rotation of the disc on the articular surface of the condyle. The disc and its attachment to the condyle are called the condyle–disc complex; this is the joint system responsible for rotational movement in the TMJ.

53. 2. The second system is made up of the condyle–disc complex functioning against the surface of the mandibular fossa. Since the disc is not tightly attached to the articular fossa, free sliding movement is possible between these surfaces in the superior cavity. This movement occurs when the mandible is moved forward (referred to as translation ). Translation occurs in the superior joint cavity between the superior surface of the articular disc and the mandibular fossa. Thus the articular disc acts as a non-ossified bone contributing to both joint systems; hence the function of the disc justifies classifying the TMJ as a true compound joint.

54. Mechanism of disc control Opening If the condyle disc assembly is fully seated in centric relation, the disc is positioned at the most forward position (on top of the condyle) that the posterior ligament allows. At this position, the forces from condylar loading are directed up through the medial third of the disc and forward through the anterior surface of the condyle against the steepest part of the eminentia.

55. As the inferior lateral pterygoid muscle (+) starts to pull the condyle forward, the superior lateral pterygoid muscle (-) releases contraction to allow the elastic fibers to start pulling the disk more to the top of the condyle .

56. Maximum movement When the condyle reaches the crest of the eminence, the disc should be directly on top of the condyle as forces are directed upwardly against the flattest part of the articular eminence. At this point, the elastic fibers have rotated the disc back because the superior lateral pterygoid muscle is in a controlled release. Note how the posterior ligament (PL) (which is not elastic) becomes more lax as the disc moves back

57. Closing As the jaw closes, the condyle starts to move back and up the steeper slope of the articular eminence, so the disk must be pulled back to the front of the condyle. To accomplish this, the superior lateral pterygoid muscle (+) starts its contraction as the inferior lateral pterygoid muscle (-) releases the condyle to the elevator muscles that pull it back .

58. Closed When the condyle reaches centric relation, the disc has been pulled as far forward as the posterior ligament will allow. If the ligament is intact and has not been stretched or torn, the disc is stopped in perfect alignment with the direction of loading through the condyle. In the absence of occlusal interferences to centric relation, the inferior lateral pterygoid muscle will stay passive, even if the patient clenches. The superior belly holds its contraction to maintain the disk in its correct alignment

59. Note how the superior lateral pterygoid muscle attaches to both the disc and the neck of the condyle. This tethers the front of the disc with muscle fibers that can elongate to permit the disc to rotate to the top of the condyle, but can contract to pull the disc back when the condyle is fully seated.

60. As the disc rotates to the top of the condyle as it approaches the crest of the eminentia, the inelastic posterior ligament folds. The functional aligning of the disc is an example of the importance of the coordinated contraction and release of the neuromusculature system in harmony with mandibular function.

61. MANDIBULAR MOVEMENTS Acc to Okeson – 2 types of movements Rotational/hinge – Occurs mainly between the disc and condyle in the lower joint compartment. Translational/sliding - Occurs mainly between the articular eminence and disc (and mandible) in the upper compartment. Based on Plane of border movements: – Horizontal, Vertical (frontal) Sagittal plane movements.

62. Rotation around horizontal axis Rotation around sagittal section Translation Rotation around vertical axis

63. ENVELOPE OF MOTION Dr ulf posselt’s in 1952 first described a 3D concept of mandibular movements It was a Combination of border movements in all 3 planes: Sagittal Horizontal Frontal The envelope differs from person to person but it has the same characteristic shape The superior surface of the envelope is determined by the tooth contacts The other borders are primarily determined by the TMJ anatomy and the ligaments

64. Border Movements Define - The mandibular movements are limited by ligaments, the articular surfaces of the TMJ, and the morphology and alignment of the teeth. The outer range of movement is reproducible and called border movements. By combining the mandibular border movements in the three planes a three dimensional envelope of motion can be produced that represents the maximum range of movement of the mandible. Although it has a characteristic shape it varies from person to person.

65. BORDER MOVEMENTS IN SAGITTAL PLANE

66. ECCENTRIC MANDIBULAR MOVEMENTS Any movement of the mandible from centric occlusal position that results in tooth contact is called as eccentric movement. Types of eccentric movements: – Protrusive movements. Retrusive movements. Laterotrusive movements

67. Protrusive Movements Consists mainly of condylar translations. Sagittal Protrusive condylar path: 5-55  and mean is 30 . Sagittal protrusive incisal path: range 50-70 .

68. Lateral Movements Sagittal lateral condylar path: When lateral movement is executed, the working condyle rotates and moves outward while other, non-working condyle translates forward, medially downward orbiting around the rotating working condyle. This orbiting condylar path of working condyle is called as BENNETT MOVEMENT

69. CONCLUSION A thorough knowledge of TMJ & its relationship with surrounding structures is essential to fully comprehend normal anatomy & physiology, adaptive processes, dysfunction & pathology of the TMJ. Although numerous treatments have been advocated, none are universally effective for all patients all the time. A good Prosthodontic treatment bears direct relation with TMJ articulation since establishment of occlusion is one of the main steps in complete denture, fixed partial & removal partial dentures. Effective treatment begins with the thorough understanding of the disorder & its etiology and an appreciation of the various types of treatments is essential for effective management of the symptoms.

70. REFERENCES Okeson, JP. Management of Temporomandibular Disorders and Occlusion , 7th ed., (2003), Mosby. Zarb GA, Bolender CE. Prosthetic treatment for edentulous patients, Complete dentures & Implant supported prosthesis. 13th ed. Dawson PE. Functional occlusion from TMJ to smile design.3rd ed. Neil S. Norton. Neter’s Head And Neck Anatomy For Dentistry. 2nd Ed. Philadelphia. Elsevier Inc 2012. Irene A. Espinosa de Santillana , Ariana García-Juárez, Jaime Rebollo - Vázquez y Ana K. Ustarán -Aquino. Frequent postural alterations in patients with different types of temporomandibular disorders. Rev. Salud Pública . 20 (3): 384-389, 2018. 09-06-2019 116 Melissa E. Bender, Rosa B. Lipin , Steven L. Goudy. Development of the Pediatric Temporomandibular Joint. Oral Maxillofacial Surg Clin N Am 30 (2018) 1–9. Dania Tamimi, Elnaz Jalali , David Hatcher. Temporomandibular Joint Imaging. Radiol Clin N Am – 2017.