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Tmj /certified fixed orthodontic courses by Indian dental academy


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Tmj /certified fixed orthodontic courses by Indian dental academy

  1. 1. T M J Functional Anatomy Function must be understood before dysfunction can have any meaning. INDIAN DENTAL ACADEMY Leader in continuing dental education 12th May 2004 -Seminar
  2. 2. T M J Functional Anatomy CLASSIFICATION OF JOINTS • BASED ON ANATOMICAL CHARACTERISTICS (Structural classification) • BASED ON FUNCTIONAL CLASSIFICATION: ( type of movement) 12th May 2004 -Seminar
  3. 3. T M J Functional Anatomy STRUCTURAL CLASSIFICATION: Based on presence or absence of joint cavity: FIBROUS JOINT: CARTILAGENOUS JOINT: SYNOVIAL JOINT FUNCTIONAL CLASSIFICATION: SYNARTHROSIS: Immovable joints AMPHIARTHROSES: Slightly movable joints DIARTHROSIS: Freely movable joints: 12th May 2004 -Seminar
  4. 4. T M J Functional Anatomy SYNARTHROSIS: Immovable joints SUTURE: sutura = seam Fibrous joint composed of thin layer of dense fibrous connective tissue that unites bones of the skull GOMPHOSIS: to bolt together Cone shaped peg fits into a socket eg tooth into alveolar bone through periodontal ligament SYNCHRONDROSIS: syn= together , chondros=cartilage Cartilaginous joint in which connective material is hyaline cartilage eg epiphyseal plate 12th May 2004 -Seminar
  5. 5. T M J Functional Anatomy AMPHIARTHROSES: SYNDESMOSIS:band /ligament fibrous joint in which there is considerably more fibrous connective tissue than in a suture. The fit of the bones is not so tight. Some amount of flexible movement. EG distal articulation between fibula and tibia SYMPHYSIS:growing together Cartilaginous joint in which connecting material is broad flat disc of fibro cartilage EG intervertebral discs.pubic symphysis 12th May 2004 -Seminar
  6. 6. T M J Functional Anatomy DIARTHROSIS: Also known as synovial joints. Presence of Synovial cavity and articular cartilage a characteristic feature. Based on types of movement: GLIDING : eg intercarpal joint HINGE eg: elbow joint/ ankle CONDYLOID eg: joint between radius and carpals PIVOT eg: joint between atlas and axis SADDLE eg : joint between carpus and thumb BALL AND SOCKET: eg : shoulder/ hip joint 12th May 2004 -Seminar
  8. 8. T M J Functional Anatomy SYNOVIAL JOINT: Specialized endothelial cells form a synovial lining and forms the synovial fluid which fills both joint cavities and performs two functions:  Medium for metabolic exchange: as the articular surfaces are avascular Lubricant during function: Two mechanisms by which lubrication occurs: BOUNDARY LUBRICATION: primary mechanism;synovial fluid forced from one region to another by movement of the joint itself. WEEPING LUBRICATION: The articular surfaces itself absorb some amount of synovial fluid which due to the pressure during function is forced in and out of the articular tissues and provided the medium for metabolic exchange. This occurs only during compression but not all other movements. 12th May 2004 -Seminar
  10. 10. T M J Functional Anatomy CONDYLAR HEAD • The oval condylar head is shaped like a rugby ball • The lateral pole is slightly at a a lower level to the medial pole • The long axis makes a line of 140 degrees with the line joining the external acoustic meatus The cartilage layer is thicker laterally and posteriorly suggesting the growth direction is more active in these areas. Anteromedially the cartilage becomes thin early and bone forms in this region of attachment of the lateral pterygoid 12th May 2004 -Seminar
  11. 11. T M J Functional Anatomy The glenoid fossa Shallow oval depression in the infratemporal area Bone of the deepest part is quite thin and shows that this part of the joint is not designed to play an active functional role in the joint. The articular eminence The two slopes of the articular eminence are considered to be a functional part of the joint. The posterior slope resorbs with edentulism 12th May 2004 -Seminar
  12. 12. T M J Functional Anatomy Muscles of mastication mastication is a a harmonious and skillful activity which requires the presence and co ordination of not only the muscles of mastication but also the supra infrahyoid muscles, and the facial muscles 12th May 2004 -Seminar
  13. 13. T M J Functional Anatomy The strongest of the masticatory muscles The temporalis Divided into three parts Well developed in carnivores and animals requiring a strong bite force Temporalis muscle tendon It elevates the mandible when it contracts. Contraction of the anterior part raises the mandible Contraction of the middle part elevates and retrudes the mandible 12th May 2004 -Seminar
  14. 14. T M J Functional Anatomy Powerful elevator muscle The masseter Superficial muscle helps in protruding the mandible Deep portion helps in stabilizing the condyle against the articular eminence when biting in a protruded position. Unilateral movement helps in lateral movement of the mandible Well developed in ruminants Deep portion Superficial portion 12th May 2004 -Seminar
  15. 15. T M J Functional Anatomy The medial pterygoid muscle Originates from the pterygoid fossa and extends downwards backwards and outwards to insert in the medial side of the ramus of the mandible forming a sling along with the masseter at the angle of the mandible. It assists in closing of the jaw and contraction of the muscle also causes protrusion. 12th May 2004 -Seminar
  16. 16. T M J Functional Anatomy The lateral pterygoid muscle Superior lateral pterygoid muscle Originates form the infratemporal surface of the greater wing of the sphenoid, extends almost horizontally backward and outward to insert on the articular capsule the disc and the neck of the condyle. 60 to 70% of the fibres attach to the condyle and the rest to the disc. Plays an active role not during opening but during closing (power stroke) 12th May 2004 -Seminar
  17. 17. T M J Functional Anatomy Originates at the outer surface of the lateral pterygoid plate and extends backward upward and outward to insert into the neck of the condyle. When there is bilateral contraction the condyles are pulled down the articular eminences and the mandible is protruded. Unilateral contraction causes a mediotrusive movement of that condyle and lateral movement of the mandible to the other side . The inferior lateral pterygoid is active during opening in contrast to the superior part. 12th May 2004 -Seminar
  18. 18. T M J Functional Anatomy Soft tissue components of the TMJ Articular disc, capsule, ligaments and muscles 12th May 2004 -Seminar
  19. 19. T M J Functional Anatomy Articular Disc Articular disc Superior head of the lateral pterygoid Inferior head of the lateral pterygoid 12th May 2004 -Seminar
  20. 20. T M J Functional Anatomy ARTICULAR DISC Divides the joint into two compartments According to Rees divided into 4 parts: Anterior band –thickened Intermediate band- narrow and thin Posterior band – again thick Bilaminar zoneupper part having ELASTIC fibres and attaching to the posterior margin of the glenoid fossa and the tympano squamous fissure, forms the posterior border of the upper compartment. lower part: mainly collagen fibres and attached to neck of condyle. Posterior border of the lower compartment. 12th May 2004 -Seminar
  21. 21. T M J Functional Anatomy Articular disc Joint capsule Lateral ligament of the TMJ Articular disc has the shape of a laterally wide ovoid. In frontal section the disc is wedge shaped thicker medially and thinner laterally 12th May 2004 -Seminar
  22. 22. T M J Functional Anatomy Articular disc Joint capsule The intermediate band: It is the functional zone of the disc Blood vessels are rarely found here in the intermediate part of the disc 12th May 2004 -Seminar
  23. 23. T M J Functional Anatomy Unlike other synovial joints the TMJ condyle and temporal bone do not fit together in the absence of the disc. The disc fills the wedge like gap and stabilizes the join during rotation and translation. Normally there is no space between the disc and the articulating bones except the antero- superior and inferior recesses and the postero -superior and inferior recesses. These recesses are filled with synovial fluid and movement of the joint squeezes them into the other recesses so a thin film of lubricant is obtained on the moving parts. The disc also acts as a shock absorber. 12th May 2004 -Seminar
  24. 24. T M J Functional Anatomy LIGAMENTS: They are made up of collagenous connective tissue which do not stretch and do not actively participate in the normal function They act as guide wires restricting certain movements while permitting certain others. They restrict movement mechanically as well as through neuro muscular reflex activity. Ligaments do not stretch. They can be elongated by traction forces but once they have been elongated joint activity is usually 12th May 2004 -Seminar compromised.
  25. 25. T M J Functional Anatomy Functional ligaments which support the TMJ : • The collateral ligaments (discal) • Capsular ligament • TM ligament Accessory ligaments: Stylomandibular ligament. Sphenomandibular ligament 12th May 2004 -Seminar
  26. 26. T M J Functional Anatomy The collateral ligaments (discal) Attach the medial and lateral poles of the articular disc to the poles of the condyle. They are two in number:- medial and lateral . They function in allowing the disc to move passively with the condyle as it glides anteriorly and posteriorly. They also allow the disc to be rotated anteriorly and posteriorly on the articular surface of the condyle.. Thus these ligaments are responsible for the hinging movements of the condyle which occurs in the lower compartment. 12th May 2004 -Seminar
  27. 27. T M J Functional Anatomy Capsular ligament The capsular ligament encompasses the joint retaining the synovial fluid. It is fibroelastic, very well vascularised and well innervated and provides proprioceptive feedback regarding the position and movement of the joint. . Capsular ligament Lateral ligament 12th May 2004 -Seminar
  28. 28. T M J Functional Anatomy TM ligament It has two parts outer oblique and an inner horizontal. The outer part extends from the articular tubercle to the neck of the condyle The outer oblique part has the following functions:  It restricts excessive dropping of the condyle and therefore limits the normal opening of the mandible. Secondly during opening of the mouth, the condyle rotates till this ligament becomes tight as its point of insertion is rotated posteriorly. When it becomes taut the neck cannot rotate any further. This unique feature is found only in humans preventing excessive rotation for the mandible from impinging on the vital mandibular and retromandibular structures behind the jaw. 12th May 2004 -Seminar
  29. 29. T M J Functional Anatomy the inner horizontal part extends backwards from the articular tubercle to insert into to the lateral pole of the condyle and posterior part of the articular disc. Function: The inner horizontal portion protects the posterior retrodiscal tissues from trauma and also prevents the lateral pterygoid muscle from over lengthening. 12th May 2004 -Seminar
  30. 30. T M J Functional Anatomy Accessory ligaments: Sphenomandibular ligament Stylomandibular ligament. It becomes taut when the mandible is protruded and thus limits the excessive protrusive movements of the mandible. 12th May 2004 -Seminar
  31. 31. T M J Functional Anatomy Vascular supply: Superficial temporal artery Middle meningeal artery Maxillary artery Innervation: Auriculotemporal nerve Deep temporal and masseteric nerve VASCULAR SUPPLY AND INNERVATION OF THE JOINT Others : deep auricular , anterior tympanic, ascending pharyngeal 12th May 2004 -Seminar
  32. 32. T M J Functional Anatomy JAW MOVEMENTS AND JOINT MECHANICS 12th May 2004 -Seminar
  33. 33. T M J Functional Anatomy The border area of the movement of the mandibular incisor point is known as Posselt’s figure 12th May 2004 -Seminar
  34. 34. T M J Functional Anatomy MOVEMENTS IN THE MANDIBLE: Two types of movement occur in the mandible: Rotational Translational Rotation is the movement of a body around its axis The mandible can rotate in all three reference planes Horizontal/Frontal/Sagittal Translation movement: It is defined as a movement in which every part of the moving body has the same direction and velocity of movement. Translation occurs in the superior cavity of the joint while rotation occurs in the inferior cavity of the joint. 12th May 2004 -Seminar
  35. 35. T M J Functional Anatomy SAGITTAL PLANE BORDER MOVEMENTS AND FUNCTIONAL MOVEMENTS: Mandibular motion in the sagittal direction has 4 distinct movement components: *posterior opening border movement *anterior opening border movement *superior contact border movement *functional movements 12th May 2004 -Seminar
  37. 37. T M J Functional Anatomy HORIZONTAL PLANE BORDER AND FUNCTIONAL MOVEMENTS The horizontal plane border movements are traced by the gothic arch tracing. The mandibular movements are in a rhomboid pattern with 4 distinct movement components. Left lateral border Continued left lateral border with protrusion Right lateral border Continued right lateral border with protrusion. 12th May 2004 -Seminar
  38. 38. T M J Functional Anatomy Functional movements: Centric relation Intercuspal position Area used just before swallowing Area used in early stage of mastication End to end position of anterior teeth During chewing the range of jaw movements begins some distance from the maximum Intercuspal position but as the food is broken down into smaller particle sizes the jaw action comes closer to the ICP . The exact position of the mandible during chewing is dictated by the occlusal configuration 12th May 2004 -Seminar
  39. 39. T M J Functional Anatomy FRONTAL BORDER (VERTICAL) AND FUNCTIONAL MOVEMENTS: The border movement has a shield shaped movement along with the functional movement. Left lateral superior border Left lateral opening border Right lateral superior border Right lateral opening border 12th May 2004 -Seminar
  40. 40. T M J Functional Anatomy ENVELOPE OF MOTION: 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. 12th May 2004 -Seminar
  41. 41. T M J Functional Anatomy In normal intercuspal position, the force generated by the masticatory muscles is concentrated on the teeth thus the joint receives only a small amount of the force. 12th May 2004 -Seminar
  42. 42. T M J Functional Anatomy 8 7 1 2 6 3 5 4 The work of GIBBS is well know in the field of masticatory movements. Gibbs classified one masticatory cycle into 8 steps:12th May 2004 -Seminar
  43. 43. T M J Functional Anatomy CLENCHING IN THE INCISOR REGION Superficial portion of the masseter and the medial and lateral pterygoid work during this. Lateral pterygoid is especially active In an individual without molars and premolars the same muscles work with the exception of the temporalis. 12th May 2004 -Seminar
  44. 44. T M J Functional Anatomy UNILATERAL CLENCHING IN THE MOLARS The temporalis on the working side is active whereas the one on the balancing side is not. In contrast the lateral pterygoid on the working side is inactive while the one on the balancing side is active. The masseter contracts powerfully on the working side while slightly but firmly on the balancing side. 12th May 2004 -Seminar
  45. 45. T M J Functional Anatomy CLENCHING IN THE INTER CUSPAL POSITION All the muscles of mastication work except the lateral pterygoids on both sides 12th May 2004 -Seminar
  46. 46. T M J Functional Anatomy MASTICATORY MOVEMENT The temporalis works through all stages of the cycle. On the working side all the muscles are in action except the lateral pterygoid. On the balancing side the temporalis and the medial pterygoid work strongly while the lateral pterygoid works slightly 12th May 2004 -Seminar
  47. 47. T M J Functional Anatomy Thus the workings of the masticatory system are extremely complex. It is a remarkable phenomenon that in most instances it functions without complication in a person’s lifetime. When the breakdown does happen however a situation is produced which is as complicated as the system itself. Therefore without a sound understanding of normal function dysfunction cannot be comprehended… 12th May 2004 -Seminar
  48. 48. T M J Functional Anatomy Thank you For more details please visit 12th May 2004 -Seminar