Growth and development of temporo mandibular joint / invisible aligners


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Growth and development of temporo mandibular joint / invisible aligners

  2. 2. CONTENTS Introduction Evolution of TMJ Embryology Growth and Development Age changes Histology Functional Anatomy and Biomechanics  Movements of TMJ TMJ disorders Summary and Conclusion References
  4. 4. Evolution of TMJ The agnatha, the earliest type of vertebrae, had its mouth opening on the ventral side anteriorly along the vertebral axis. This opening led through an oropharyngeal channel to the gut proper. Slits that opened to the outside functioned both for respiration and food filtration, and were moved simultaneously in cooperation with the mouth by a series of cartilages called gill arches. A GILL ARCH had an internal bend and the turning point of this bend was a synarthosis, which was considered to be the earliest form of a jaw joint. This structure remains as an epiceratobranchial joint in the present day shark.
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  6. 6. GNATHOSTOMES -1st and 2nd arches disappeared into the skull. -3rd and 4th arch’s began to function in the prey capture: the apparatus of jaw As evolution proceeded; -A more highly developed moveable jaw joint appeared in OSTEICHYTES -Formed by gill arches, the cartilagenous jaw was covered by second jaws. -Teeth developed in the bony plates around the mouth. -Amphibians
  7. 7. In amphibians – had a dentary in the anterior end of original cartilagenous jaw. At posterior end it articulated with the quadrate bone, a structure of maxilla. Mammal like reptilia Ex: Aligator Is composed of a number of bony segments, of which only the dentary is retained in the human
  8. 8. Two of these segment, quadrate and articulate both derived from Meckel’s cartilage (1st branchial arch) constitue the non-mammalian jaw joint i.e. PRIMARY JOINT OR QUADRATO-ARTICULAR JOINT are incorporated in all mammals into the middle ear as: -Incus -Malleus -Therefore the incudomalleolar joint is thus homologus with repitilia jaw joint
  9. 9. Associated with the formation of ear ossicles, a new jaw joint TMJ made its first appearance in mammals. Secondary joint / Squamosodentary joint [As it is present between squamous part of temporal bone and the mandible (dentary)]. - One can imagine this evolutionary transmission occurring by means of a bony process which appeared on the mandibular anterior to quadratoarticular joint which at one time became large enough to contact the skull.
  10. 10. Difference in Mammalian jaw-joint Non mammalian jaw-joint A) Convex joint surface Concave B) Intra-articular disk Absent
  11. 11. EMBRYOLOGY -Develops late in embryonic life. -Compared with large joints of extremities. -Associated with its late evolutionary development. -During the 7th prenatal week, the jaw joint lacks: -Condylar growth cartilage. -Joint cavities. -Synovial tissues -Articular capsule. 2 skeletal elements : mandible and temporal bone are not yet in contact with each other.
  12. 12. 7 week old embryo -Meckel’s cartilage extends all the way from chin to base of the skull. -Serves as a scaffolding or strutt against which the mandible develops. -Provides a temporary articulation between mandible and base of the skull until TMJ takes over. -Near end of fetal life Meckel’s cartilage completes its transformation: -Incus -Malleus -Anterior ligament of malleus -Sphenomandibular ligament Meckel’s cartilage plays an a basic role in setting the evolutionary stage for the emergence of this
  13. 13. Articular Disc: -Earliest appearance in 6 week old embryo. -Muscular derivative of 1st branchial arch. -Disc analge- vague layer of mesenchyme stretching across upper end of mandibular ramus. -No capsule. -No condyle.
  14. 14. Articular Disc: -At its anterior end, mesenchymal analge extends laterally from superior border of LPM, to medial side of masseter muscle. -At the end of 6th week, lateral pterygoid inserts not on the mandibular but on the posterior end of Meckel’s cartilage. -During 7th week – (LPM) joins upper end of mandibular ramus; also continues posteriorly beyond this point with mesenchyme analge des abv; these 2 structures insert in common part of Meckel’s cartilage which becomes the malleus.
  15. 15. At 7 weeks: the future condyle is still only a condensation of mesenchyme resting on osseous lamella, which forms the mandibular ramus. 12 week – condylar growth cartilage makes its 1st appearance and begins to develop a hemi-spherical articular surface. By 13th week – condyle and articular disc having moved up into contact with temporal bone. Only when such articular contact has been made do the joint cavities develop. Inferior space appearing first. Disc begins to get compressed. When central portion of disc is compressed this part becomes avascular.
  16. 16. The articular capsule: -Becomes recognizable during twelth week as a faint cellular condensation along the medial and lateral sides of joint connecting mandible with temporal bone. -Articular disc merges peripherally with these condensations. -Formation of capsule posterior to joint does not occur until twenty-second week; when the Glaserian fissure; becomes narrow; encroaching upon Meckel’s cartilage as it passes into middle ear. -Articular disc becomes intercepted at the Glaserian fissure, loses its continuity with malleus and develops definitive attachment to anterior lip of GF. -Joint cavities are now lined by synovial tissue and according to Symons (1952), temporal bone now shows area of secondary cartilage in medial part of the
  17. 17. By 26th week: All components of TMJ present except articular eminence. Meckel’s cartilage still extends through GF, but by thirty- first week is transformed into sphenomandibular ligament. By 39th week: Ossification of bones in this region has proceeded to the point where; ligament gains its apparent attachment to spine of sphenoid.
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  19. 19. HISTOLOGY OF TMJ Composed of 4 distinct layers: -Articular. -Proliferative. -Fibro cartilaginous. -Calcified cartilage.
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  22. 22. The growth of face and cranium involves two basic types of growth changes: 1) Displacement 2) Remodelling - Both these process, together constitute the growth mechanism of craniofacial skeleton. - One of the most familiar phrases in facial biology is that the face grows downwards and forwards. - As mandibular moves forward and downward, it grows upward and backward at the same time by an equal amount. - The process of mandibular growth is complex; does not merely involves condylar growth to accomplish these changes. - About half of the periosteal surfaces of bone (mand) have fields that are characteristically resorptive in character and about
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  24. 24. -For example, mandibular ramus grows posteriorly, with about half of outside surfaces undergoing resorption and about half deposition. -The ramus at the same time becomes broader because the amount of posterior bone deposition exceeds the amount of anterior resorption on the various surfaces. -As the ramus grows posteriorly, the mandibular condyle grows upward and backward by an endochondral mode of bone formation, in contrast to intermembranous manner of growth in other parts of the ramus.
  25. 25. -The bone located where the condyle used to be during past growth stages is remodelled, successively into mandibular neck and a part of the ramus. -The endosteal surface of the mandibular neck, rather than the outersurface, is oriented so that it faces the upward and backward of condylar growth.
  26. 26. The condyle as a major growth site: -The condyle has been singled out as a special site (centre) because it has a distinctive growth cartilage, which provides certain special function during growth. -The posterior and superior manner of growth of mandibular ramus required an endochondral type of bone formation at its condylar junction with the cranial floor because of the surface compression involved.
  27. 27. -Cartilage of the condyle is a secondary or adventitious cartilage as it was developed secondarily often the original primary cartilage was modified for a different function elsewhere in the skull. -The upward and backward growth of the condyle has a resultant push effect against the basicranium, with a subsequent displacement of the entire mandibular downward and forward. (Condylar thrust concept).
  28. 28. TMJ in the first decade of life: -At birth, the mandible as a whole continues the exuberant, but progressively diminishing period of overall growth that was begun during the last trimester in utero. -During the first year of life the condyle : ↓ vascularization, entire growth cartilage layer becomes significantly thinner. This continues upto the third year.
  29. 29. -Morphologic changes take place from birth to the end of mixed dentition by 8 months: Enlargement of articular eminence and post glenoid region. -During this time tympano-squamosal tissue begins to close as the postglenoid process becomes fused with the tympanic plate. -By 2 ½ years the articular eminence increase from 2 to 4mm. This is due to resorption of the bone in the roof of the mandibular fossa and bone deposition anterior and posterior to the fossa leading to formation of ‘S’ shape curve.
  30. 30. The process continues so that by 6-7 years the articular eminence enlarges to 5-6mm in height. By approximately 6-7 years of age Articular layer of condyle becomes thicker Cartilage layer becomes thinner – 0.3mm Underlying trabeculae becomes progressively thicker. Growth continues - 7 to 12 years of age. Articular disk – highly vascularized and rich in fibroblasts during the 1st few years. Progressively the vascularization decreases. Posterior surface of the ramus the condylar neck and the condyle are sites of active skeletal growth leading to relocation of the mandibular condyle in superior and posterior direction (V principle of Enlow).
  31. 31. TMJ in 2nd and 3rd decade: Characterized by progressive slowing of growth process. By 13-15 years decreased thickness of cartilage layer. Presence of proliferative layer atleast till age of 18 years. A cortical bone cap coalescing with subchondral trabecular bone by 10-12 years of age. This increases in thickness upto 3rd decade of life. Bone cap is completed by 20 years of age although cartilage and sparse cartilage cells remain.
  32. 32. ADULT TMJ -Cartilage completely replaced by the bone around the beginning of 4th decade. -Articular tissue: Relatively unchanged – may undergo changes depending on biomechanical loading. -Deep to the articular layer in the region where subchondral growth cartilage was located a chondroid type bone may be found which directly overlies the bone cap.
  33. 33. -This marks the end of active growth of the condyle. -In older adult temporal fossa: less pronounced chondroid layer. -Articular eminence : is made of chondroid bone. -Up through the 5th decade mandibular fossa became more deep and articular eminence becomes more prominent. -As age progresses further there is flattening of the articular fossa and decrease in prominence of the articular eminence.
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  37. 37. FUNCTIONAL ANATOMY (1) Bony components -Condylar head -Glenoid fossa -Articular eminence (2) Muscles 1) Muscles involved in mastication. 2) Facial muscles. 3) Muscles of the neck (3) Soft tissue -Articular disc -Joint capsule -Ligaments -Muscles attached to joint (4) Arterial Supply (5) Nerve supply (6) Lymphatic drainage
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  64. 64. BIOMECHANICS OF TMJ - Complex joint system. - Compound joint – Its structure and function can be divided into 2 distinct system: i) Condyle disc complex. ii) Condyle disc complex and articulating surface of mandibular fossa. - Constant contact between joint surfaces for stability is required. - Disc space more at rest, decreases with an increase in pressure of the joint. - Retrodiscal lamina - Lateral pterygoid.
  65. 65.  Movement involving the joints has beenMovement involving the joints has been divided different phasesdivided different phases • Occlusal or rest positionOcclusal or rest position • Retruded opening phase or rotationRetruded opening phase or rotation • Early protrusive opening phase or functionalEarly protrusive opening phase or functional openingopening • Late protrusive opening phase or translationLate protrusive opening phase or translation • Early closing phaseEarly closing phase • Retrusive closing phaseRetrusive closing phase
  66. 66. OCCLUSAL OROCCLUSAL OR REST POSITIONREST POSITION • The rest position is the first step and involves a static jaw position with maximum intercuspation. • In this, the joint is in loose pack position, the connective tissue at rest • The posterior band occupies the deepest part of the mandible fossa • The intermediate zone and the anterior band lies between the condyle and posterior slope of the eminence
  67. 67. RETRUDED OPENING PHASERETRUDED OPENING PHASE OR ROTATIONOR ROTATION •The condyle rotates and moves 5 to 6 mm inferior to the intermediate zone •The condyle joint surface glides forward and the medial pole of the condyle moves anterosuperiorly and the lateral pole moves posteroinferiorly •The shape of inferior compartment changes the most •The upper lateral pterygoid relaxes and the lower lateral pterygoid contracts •The posterior connective tissues is in a functional state of rest
  68. 68. EARLY PROTRUSIVE OPENINGEARLY PROTRUSIVE OPENING PHASE OR FUNCTIONAL OPENINGPHASE OR FUNCTIONAL OPENING •The condyle moves inferiorly and anteriorly approximately 6 to 9 mm below the intermediate zone. •The disk and the condyle experience the short anterior translatory glide •The upper and lower head of lateral pterygoid contract to guide the disk and the condyle shortly forward •The posterior connective tissues is in a functional tightning
  69. 69. LATE PROTRUSIVE OPENINGLATE PROTRUSIVE OPENING PHASEPHASE OR TRANSLATIONOR TRANSLATION • The condyle moves inferiorly and anteriorly beneath the anterior band i.e there is full opening more, space develops in the superior compartment • The upper and lower head of Lateral pterygoid contract to guide the disk and the condyle fully forward • The posterior connective tissues tightens
  70. 70. EARLY CLOSING PHASEEARLY CLOSING PHASE The condyle translates posteriorly, about 6 to 9 mm, to the intermediate zone There is simultaneous reduction of space posteriorly in the superior compartment
  71. 71. RETRUSIVE CLOSING PHASERETRUSIVE CLOSING PHASE • The condyle rotates superiorly but remains inferior to the posterior band • This movement reduces the space in the inferior compartment • The upper head of the lateral pterygoid contracts and • The lower head of the lateral pterygoid relaxes • This tightens the mandibular attachment, and forces blood from the posterior compartments • The posterior connective tissues returns to the functional rest movements
  72. 72. TMJ DISORDERS Classification: 1) Growth disorders and the joint a) Developmental disorders. b) Acquired disorders. c) Neoplastic disorders. 2) Masticatory muscle disorders: a) Protective muscle splinting. b) Muscle hyperactivity or spasm. c) Myositis (muscle inflammation). 3) Disk interference disorders (internal derangement) a) Incoordination. b) Deformation of articular disk. c) Partial anterior disk displacement. d) Anterior disk displacement with reduction. e) Anterior disk displacement without reduction. f) Anterior disk displacement with perforation. g) Posterior disk displacement.
  73. 73. 4) Problems that result from extrinsic trauma: a) Tendonitis. b) Myositis. c) Traumatic arthritis. d) Dislocations. e) Fracture. f) Internal derangements.
  74. 74. 5) Degenerative joint disease: • Arthrosis (non-inflammatory phase). • Osteoarthritis (inflammatory phase). • Osteochondritis disecans. 6) Inflammatory joint disorders: • Synovitis and capsulitis • Retrodiskitis. • Inflammatory arthritis
  75. 75. 7) Chronic mandibular hypomobility: • Ankylosis. • Fibrosis. • Contracture of elevator muscle. • Internal disk derangement. 8) Post surgical problems
  76. 76. Diseases affecting the TMJ are primarily inflammatory and degenerative, while developmental, metabolic and neoplastic conditions are rare occurrences. Developmental anomalies: -Congenital Genetic / Prenatal / Postnatal Trauma Nutritional deficiencies etc. Acquired
  77. 77. Condylar agenesis -Is frequently associated with various symptoms. - if unilateral pronounced facial asymmetry under developed mandible leads to distortion and depression of that side of the face. -Macrostomia. -Absence of external ear. -Alterations in dental occlusion. -Bilateral condylar agenesis may present with symmetrical severe underdevelopment of the mandible.
  78. 78. Condylar Hypoplasia -More frequent -Causes: infection and trauma -C/F: Facial deformity -Limitation of lateral excursion. -Shift of mandibular midline during opening of mouth. Double mandibular condyle: Etiology, embryologic, traumatic……….. -Usually unilateral -Two condyles with one mandibular neck are
  79. 79. Condylar hypoplasia: Causes: Infection Trauma Clinical features -Symmetric enlargement of entire condylar process. -Limited movements. -In adults lateral displacement and open
  80. 80. ANKYLOSIS Defined as chronic hypo mobility or immobility of a usually moveable articulating surface. Causes: - Infection, trauma. Classification: 1. Unilateral / bilateral. 2. Fibrous / bony. 3. Partial / complete. 4. True / false.
  81. 81. Degenerative Joint Diseases: -Osteoarthritis. -Non inflammatory process caused by local disease involving one particular joint. -Etiology is multifactorial: systemic factors, mechanical stress, trauma. -Other factors: tooth loss, Occlusal interferences, Excessive forces of muscles in bruxism. C/F: Crepitation, unilateral pain, feeling of stiffness after a period of inactivity. Treatment: NSAIDS, heat, soft diet, occlusal splints, intra articular steroids,
  82. 82. MPDS: Is a pain referred from a localized tender area, a trigger point, in a taut band of skeletal muscle, including muscles of mastication. Laskin stated that TMJ pain dysfunction syndrome is a misnomer because the diorder was primarily related to masticatory muscle spasm.
  83. 83. Signs and symptoms: Unilateral, dull pain in the ear or preauricular region. Tenderness of one or more muscles of mastication on palpation. Limitation or deviation of the mandible on opening. Causes: Chronic microtrauma, overuse, irregularities in occlusion, posterior bite collapse, deep overbite- overjet
  84. 84. Treatment: •Treatment of emotional and physical components. •Reviewing history of patients problems. •Placebo drugs, splints or occlusal equilibration patient reassurance. •Spray and stretch : fluoromethane refrigerant spray. •Injection LA at trigger point. •Soft diet. •NSAIDs •Discontinuing parafunctional habits. •Occlusal splint…….
  85. 85. CONCLUSION The efforts of the prosthodontist to record the movements of the TMJ and to reproduce them on the articulator have been the chief stimulus for studies on the functional structure of this joint. In order to understand fully the nature of this joint, one must begin with its evolutionary history, for its popular evolution explained its astonishing embryological development, from which comes its unique gross and histological structure, all of this reaching final clinical significance in the various functional and morphologic disorders seen in this joint.
  86. 86. References: 1. Boucher: Prosthodontic treatment for Edentulous Patients. 2. Donald H.Enlow : Essentials of Facial growth. 3. Laskin : Temporomandibular Joint 4. Orban’s: Oral Histology and Embryology. 5. Sharry: Complete denture Prosthodontics. 6. Sheldon Winkler : Essentials of Complete Denture Prosthodontics. 7. Y.Ide: Anatomy of TMJ 8. Zarb : Temporomandibular Disorders.
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