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Mandibular movements /cosmetic dentistry courses

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Mandibular movements /cosmetic dentistry courses

  3. 3. MandibleMandible The mandible is the largest of all the facial bones and is the only bone of the facial bones that has the ability of movement.
  4. 4. mandibular movements ”any movement of the lower jaw”any movement of the lower jaw” by Glossary of prosthodontics – 8
  5. 5.  They are 1. Muscles of mastication 2. Supra and infra hyoid muscles Muscles of mandibular movements
  6. 6. Muscles of mastication  Masseter  Temporalis  Lateral pterygoid  Medial pterygoid
  7. 7. Supra hyoid muscles  Digastric  Stylohyoid  Mylohyoid muscle  Geniohyoid muscles
  8. 8. Mandibular movements can be broadly classified : Based on the extend of movement border movements intra border movements - functional movement - Parafunctional movement Based on the dimension (or) Based on the movement  Rotational  Translational Based on the type of movements - hinge movement - protrusive movement - retrusive movement - lateral movement 1.lateral rotation or laterotrusion 2.lateral translation or Bennett movement2.lateral translation or Bennett movement - immediate side shift - precurrent side shift - progressive side shift
  9. 9. BASED ON THE EXTEND OF MOVEMENT BordermovementsBordermovements “mandibular movements at the limits dictated by anatomic structures, as viewed in a given plane”-GPT • Extreme movements in the horizontal plane • Extreme movements in the sagittal plane • Extreme movements in the coronal plane • Envelope of motion
  10. 10. EXTREME MOVEMENTS IN THE HORIZONTAL PLANE :  Traditionally a device called "GOTHIC ARCH" is used to record this  When mandibular movement are viewed in horizontal plane, a rhomboid shaped pattern is seen
  11. 11.  It has 4 distinct movements:  Left lateral border  Continued left lateral border  Right lateral border  Continued Right lateral border with protrusion
  12. 12. LEFT LATERAL BORDER:  Left condyle: Rotating condyle/-working condyle  Right condyle: orbitating condyle/non working condyle
  13. 13. CONTINUED LEFT LATERAL BORDER MOVMENT:  With the mandible in the left lateral border position left lateral pterygoid muscle contracts along with right inferior lateral pterygoid muscle causing left condyle to move anteriorly and to the right.  As the right condyle is in its maximum anterior position the by left condyle moves into maximum anterior position to make the mandible midline match the face
  14. 14. RIGHT LATERAL BORDER MOVEMENTS:  Right Condyle : Rotating / Working Condyle  Left Condyle: orbitating / non- Working Condyle
  15. 15. CONTINUED RIGHT LATERAL BORDER MOVEMENT:  With the mandible in the right lateral border position contraction of the right inferior lateral pterygoid muscle along with continued contraction of the left inferior lateral pterygoid will cause the right condyle to move anteriorly and to the left
  16. 16. Mandibular border movements in horizontal plane recorded at various degrees of mouth opening. 1.Left lateral, 2.continuous left lateral, 3.right lateral, 4.continuous right lateral, CR – centric relation, ICP – inter cuspal position
  17. 17. EXTREME MOVEMENTS IN THE FRONTAL PLANE :  Border movements in this plane produce a charecteristic “shield tracing”  This has four movement components.  Left lateral superior border  Left lateral opening border  Right lateral superior border  Right lateral opening border
  18. 18. Left lateral superior border movements  with the mandible in maximum inter cuspation, a lateral movement is made to the left and the recording device will generate a inferiorly concave path.
  19. 19. LEFT LATERAL OPENING BORDER MOVEMENT  From the left lateral superior border position an opening movement of the mandible produces a laterally convex path.  As maximum opening is approached ligaments tighten and produce medially directed movement that causes a shift back in the Mandibular midline to coincide with midline of the face.
  20. 20. RIGHT LATERAL SUPERIOR BORDER MOVEMENTS  with the mandible in maximum inter cuspation, a lateral movement is made to the right and the recording device will generate a inferiorly concave path.
  21. 21. RIGHT LATERAL OPENING BORDER MOVEMENTS:  As maximum opening is a approached, ligaments tighten and produce a medially directed movement that causes a shift back in the mandibular midline to coincide with the midline by the face to end this left opening position
  22. 22. EXTREME MOVEMENTS IN THE SAGITTAL PLANE :  A charecteristic “beak tracing” will be formed while recording border movements in the sagittal plane  This has four distinct movement components  posterior opening border  anterior opening border  superior contact border  functional border
  23. 23. Posterior opening border movements  This occurs in 2 stage hinging movements  I phase: The condyles are positioned in the most superior positions in the articular fossa [that is terminal hinge position]
  24. 24.  II phase: at this phase the temperomandibular ligament tightens and continued opening results in an anterior and inferior translation and the axis of rotation of mandible shifts to the ramus as condyles translate
  25. 25. Anterior opening border movements:  This is generated by the contraction of the inferior lateral pterygoids after the maximum mouth opening
  26. 26. SUPERIOR CONTACT BORDER MOVEMENTS:  This is characterized by the occluding surface of teeth.  Its precise de-lineation depends on 5 factors  The amount of variations between centric relation and maximum intercuspation  The steepness of cuspal inclines.  Amount of vertical and horizontal overlap of anterior teeth  The lingual morphology of the maxillary anterior teeth  The general inter arch relationship the teeth.
  27. 27. FUNCTIONAL MOVEMENTS  These occur during functional activity.  They usually take place with in the border movement so they are considered free movements.  These movements require Inter Cuspal Position. so they start below the Inter Cuspal Position. 1.Posterior opening border, 2.Anterior opening border, 3.Superior contact border, 4.Functional movement
  28. 28. Clinical rest position (C.R.P) :  When mandible is at rest it is found to be located 2-4mm below the Inter Cuspal Position and called so.  And Clinical Rest Position doesn't mean that the muscular have their least myographic activity  The muscles of mastication are at their lowest activity when the mandible is placed at app 8mm interiorly and 3mm anteriorly to the Inter Cuspal Position.
  29. 29. POSTURAL EFFECTS OF FUNCTIONAL MOVEMENTS:  When the head is positioned erect upright the postural position of the mandible is located 2-4mm below the Inter Cuspal Position.  If the face is directed approximately 45 degrees upward the postural position of the mandible will be altered to a slightly restricted position
  30. 30. ALERT FEEDING POSITION  Direction of face during eating is down ward 30 degrees and this is called so,  In this the mandible shifts slightly anterior to the upright position so at this position the contraction of elevator muscular occur, the contacts will occurs anterior to Inter Cuspal Position.
  31. 31. DRINKING POSITION:  A 45 degree head extension is also a significant position.  In this the mandible in maintained much posterior to the Inter Cuspal Positon
  32. 32. ENVELOPE OF MOTION:  When we combine the border movements of all the three planes, we get a three- dimensional space within which mandibular movement is possible.  This three dimensional limiting space is called as “Envelope of motion” which was first described by Posselt in 1952.
  33. 33.  The envelope of motion is longest and widest superiorly and narrows down to a point near maximum mouth opening position. Hence, as jaw separation increases, space for movement decreases to a zero at maximum mouth opening position
  34. 34.
  35. 35.
  36. 36.
  37. 37. Intra border movements : These movements occur within the envelope of motion. They are of two types namely  Functional movement  Parafunctional movements
  38. 38. FUNCTIONAL MANDIBULAR MOVEMENTS They are natural and characteristic movements that occurs during mastication, speech and yawning.  Mandibular opening  Mandibular closing  retraction  Lateral movement  Mastication  Swallowing  Speaking
  39. 39. Mandibular opening Is caused by the contraction of the  Lateral pterygoid muscle  Digastric  And other supra hyoid muscles Mandibular closing Is caused by the contraction of the  masseter  temporalis and  contralateral contraction of the lateral and medial pterygoid muscles
  40. 40. Retraction  middle and posterior fibres in the temporal muscle  supra hyoid muscles Lateral movement Right lateral movement without occlusal contact by ipsilateral contraction of posterior fibers of temporalis muscles. Right lateral movements with occlusal contact resistance by it and by some activity in ipsilateral masseter and medial pterygoid.
  41. 41. Mastication Mastication is defined as the act of chewing foods. This act is made up of rhythmic and well-controlled separation and closure of the maxillary and mandibular teeth. Each opening and closing of the mandible represents a chewing stroke.  crushing phase  grinding phase
  42. 42. Swallowing  It is a series of coordinated muscular contractions that move a bolus of food from the oral cavity through oesophagus to the stomach. It consists of voluntary, involuntary and reflex muscular activity. Speaking  The teeth, tongue, lips, floor of mouth, soft palate form the resonance chamber that affects the pronunciation during speech, chewing, sucking, and speaking
  43. 43. PARAFUNCTIONAL MANDIBULAR MOVEMENTS They Are Uncharacteristic and Unnatural Movements Like  Bruxism,  Clenching
  44. 44. Bruxism: The neuromuscular reaction to occlusal interference by seeking them out and grinding on them. When grinding is of transient nature, it is called parafunctional grinding whereas chronic destructive habit may be referred as bruxism. Clenching: It is defined as forceful clamping together of jaws in static relationship. Considerable amount of force is maintained for several seconds or even longer.
  45. 45.  Translation, when all points within a body have identical motion, and  Rotation, when the body is turning about an axes BASEDBASED ON THE DIMENSION BASED ON THE MOVEMENTON THE DIMENSION BASED ON THE MOVEMENT
  46. 46. Rotational Movement Def : Acc to Dorlands: the process of turning around an axis; movement of body about its axis Rotation occurs in 3 planes  Horizontal  Frontal [vertical]  Saggital
  47. 47. SAGITTAL PLANE.  one condyle remains in the terminal hinge position and the other moves inferiorly  This type of movement does not occur naturally  This does not occur in conjunction with other movements
  48. 48. HORIZONTAL PLANE  It is the opening and closing movement  It is refered to as hinge movement  The hinge movement is probably the pure rotational movement  In all other movements rotation around axis is accompanied by translation of the axis
  49. 49.  Mandibular movements around the frontal axis occurs when 1 condyle moves anteriorly out of the terminal hinge position with the axis of the opposite condyle remaining in the terminal hinge position  Articular eminence dictates this movement  This type of isolated movement does not occur naturally FRONTAL PLANE
  50. 50. TRANSLATION:  Def: The movement in which every point of the moving object has simultaneously the same velocity and direction
  51. 51. BASED ON THE TYPE OF THE MOVEMENTBASED ON THE TYPE OF THE MOVEMENT - Hinge movement - Protrusive movement - Retrusive movement - Lateral movement 1.lateral rotation or laterotrusion 2.lateral translation or Bennett movement2.lateral translation or Bennett movement - immediate side shift - precurrent side shift - progressive side shift
  52. 52. HINGE MOVEMENT  Purely rotational , around the horizontal axis till the patient opens his mouth to about 20-25m.This axis is called TERMINAL HINGE AXIS Proposed by Mc Collum .  The condyle rotates 10º-13º.  This Occurs while taking or crushing food .This is produced by the lateral pterygoid and the supra hyoid muscle aided by gravity .After certain amount of opening the mandible begins to glide .
  53. 53. PROTRUSIVE MOVEMENT  Occurs while incising and grasping food. This movement occurs after the condyle rotates about 13º in the TMJ. At this point the transverse hinge axis shifts to the level of the mandibular foramen.  The mandible moves forward and downwards. This movement is complete when the maxillary and the Mandibular teeth are edge to edge.
  54. 54. RETRUSIVE MOVEMENT  Occurs when the mandible is forcefully moved behind the centric relation. The patient cannot voluntarily reproduce it.  Brought about by the fibers of the temporalis, digastric and the deep fibers of the masseter. The magnitude is 0.5mm.
  55. 55. LATERAL MOVEMENT  Lateral rotation or laterotrusion  Bennett movement
  56. 56. LATERAL ROTATION  Takes place on the left or the right side. Takes place while chewing food .If the condyle is moving to the right side, the right side condyle is called the” working side” or the laterotrusive side the condyle on the left is called the “non working” or the mediotrusive side or balancing condyle.
  57. 57. In the working side any of the following five movements can take place .  laterally outwards - laterotrusion  laterally upwards - laterosurtrusion  laterally downwards - laterodetrusion  laterally forwards - lateroprotrusion  laterally backwards - lateroretrusion The non working side will move forward, downward and medially.
  58. 58.
  59. 59. BENNETT MOVEMENT  It is defined as the bodily lateral movement or lateral shift of the mandible resulting from the movement of the condyle along the lateral inclines along the mandibular fossae in lateral jaw movements. This movement is recorded in the non working side .The shift is 1- 4mm.
  60. 60.
  61. 61.  The Bennett shift is classified based on the timing of the shift in relation to the forward movement of the non working condyle.  Immediate side shift.  Precurrent side shift  Progressive side shift
  62. 62. IMMEDIATE SIDE SHIFT  Lateral translation occurs before forward movement of the non working condyle. The range is 1- 4mm.
  63. 63. PRECURRENT SIDE SHIFT  Major quotient of the lateral movement occurs during the first 2-3mm of the forward movement of the non working side .
  64. 64. PROGRESSIVE SIDE SHIFT  Lateral movement that continues linearly after 2-3mm of the forward movement of the non working condyle .
  65. 65.  Bennett Movement has 3 attributes:  Amount  Timing  Direction
  66. 66. Amount: More medial the wall is from condyle, greater will be the amount of Bennett movement. Looser the temporomandibular ligament attachment to the rotating condyle greater will be the Bennett movement.
  67. 67. Timing:  It is a function of medial wall adjacent to the orbiting condyle and attachment of temporomandibular ligament to the rotating condyle.  When the Bennett movement occurs early, a shift is seen before the condyle begins to translate from the fossa.  It is called immediate side shift side it is 0-2.6 mm, Mean value0.42mm.
  68. 68. Direction: The directions of Bennett movement depends primarily on the directions taken by rotating condyle during bodily movement. Directions taken by rotating condyle during Bennett movement is determined by; - Morphology and liagamentus attachments of TMJ undergoing rotation
  69. 69. BENNETT ANGLE  It is defined as the angle formed by the sagittal plane and the path of the advancing condyle during lateral mandibular movements as viewed in the horizontal plane – Glossary Of Prosthodontic Terms  The angle is 7.5º-12.8º.
  70. 70. FISHER ANGLE  The angle formed between the sagittal lateral condylar path and the Sagittal protrusive condylar path is called the’’ FISHER ANGLE,’’ with a mean of 5.
  71. 71. BALKWILL’S MOVEMENT  Although Bennett has described about this movement which became popularly known as Bennett movement, the original discovery of this movement should go to BALKWILL.  As early as 1870 BALKWILL observed that the mandible opened and closed on an axis that runs through the condyles, that the condyles move downwards and forwards in protrusion and also the mandible moves bodily from side to side.
  72. 72.  His observation was forgotten and remained in the archives of London library.
  73. 73. EFFECT OF BENNETT MOVEMENT ON THE CUSPAL MORPHOLOGY:  Greater the Bennett movement short the posterior cusps.  Greater the immediate side shift shorter the posterior cusps.  More superior the movement of working side of condyle shorter the posterior cusps.  More inferior the movement- longer the posterior cusps
  74. 74. STRUCTURES CONTROLLING MANDIBULAR MOVEMENT:  The structures controlling Mandibular movement are divided into two types;  Posterior controlling factors  Anterior controlling factors
  75. 75. POSTERIOR CONTROLLING FACTORS:  The Temporomandibular Joint and its suspensory ligaments,  Centres of rotation,  Axes of rotation,  Translation of these centres.
  76. 76. ANTERIOR CONTROLLING FACTORS  The contacting areas of upper and lower teeth,  inclines of cusps and nature of occlusion in centric relation and eccentric movements.
  77. 77. METHODS OF STUDYING MANDIBULAR MOVEMENT  Mandibular, particularly condyle, activities has been studied for many years by a variety of methods ranging from direct clinical observations to sophisticated electronic instruments.  1896. Warber used facial clinometer to measure mandibular movements.  1908. Bennet traced the pathway of light positioned the condyle.  1931. Hildebrand recorded condyle movements by Roentgen fluoroscopy.
  78. 78. Studies have been conducted by using.  Mechanical and cinematographic technique.  Cineradiography  More recently photo electric and electromagnetic technique  Cyber Hoby computer pantograph was developed by Hobo and Takayama in 1983, is one of the electronic pantograph that measures eccentric movements (R,L,P) by means of a small opto-electrion sensor lined to the maxilla.
  79. 79.  Other method includes.  Tracking device (gothic arch tracing)  Check bite registration (on semi adjustable articulator, o simulate mandibular movement.)  Recording of fast patterns of the teeth  Electromyography (muscles responsible for mandibular movement. Generally show increased activity during any Jaw movement. This activity and interaction of muscles for a jaw movement has been determined by electromyography).
  80. 80. Pantographic instrument  Best way study mandibular movement is by means of pantographic recordings.  The pantograph consist of two face bows.  One is a affixed to the maxilla  Other to the mandible using clutches, which attach to the teeth in their respective jaws.  Recording styli are attached to the one member and small tables (upon which tracings are made) are attached to the other member of the instrument, opposite the styli. (By Stuart, Grauger, Guichet)
  81. 81.  Now, mandible goes through a series of right and left lateral as well as protrusive excursions and the styli on one face bow scribe the path followed by condyles in each movement on the recording tables.  When the pantograph is attached to the articulator, various adjustments are made, until the movement of the articulator; various adjustments are made until the movement of the tracing tables during mandibular excursions.  Pantographic tracking can be utilized to full advantages when used with fully adjustable articulators.
  82. 82. CONCLUSION  The mandibular movements occur besides mastication in during, chewing, swallowing, vomiting, breathing, speaking, singing etc.  In other words. It palsies life promoting and their important roles in the digestive and respiratory acts, vocal performances, and more or less in every human activity and behavior.  The TMJs and the dentition are a crucial and integral aspect of the normal anatomy of the mandibular movements, differentiating it from other movement or locomotors system in the human body.
  83. 83. REFERENCES  Fundamentals of occlusion and temporomandibular disorders. Jeffery P.Okerson  occlusion : sigurd Ramfjord, Major M.Ash.  syllabus of complete denture. Charles M.Heartwell, Arthur O.Rahn.  Boucher's prosthodontic treatment for edentulous patients. George A.Zarb et al  Osseointegration and rehabilitation. Sumiya Hobo et al.  Contemporary fixed prosthodontics – Rosential,Land, Fujimoto
  84. 84.  A means for studying manidibular movements –jpd 1967;17;36-43  A method for reproduction of movements of the mandible - jpd 1962;12;873-883  Horizontal mandibular movement tranducer – Jack.N.Zafran and Gilbert.M.Zayon  A model to simulate the masticatory motion at temperomandibular joint – Marta.B.Villamil,Luciana.P.Nedel