MANDIBULAR MOVEMENTS

MANDIBULAR MOVEMENTS

1. MANDIBULAR MOVEMENTS Dr . Shari.S.R Junior Resident Govt .Dental College Trivandrum

2. C ON T ENTS Introduction Importance Methods of studying mandibular movements Factors which regulate jaw motion Classification of mandibular movements Review of literature Conclusion Reference

3. INTRODUCTION Mandibular movements are complex.

4. SIGNIFICANCE OF UNDERSTANDING MANDIBULAR MOVEMENTS Developing tooth forms for dental restorations Recording jaw relations & Understanding occlusion Arranging artificial teeth Treating TMJ disturbances Preserving periodontal health. Designing, selection and adjustment of articulators .

5. METHODS OF STUDYING MANDIBULAR MOVEMENTS Walker - Facial Clinometers Hildebrand - Roentgen Fluoroscopy Radionucleotide Tracking O p ti c al P a nt o g r ap h y Gn a thic Replicator . Ultra sound Accelerometers Videofluoroscopy Cine radiography Arcus digma Jaw motion Analyzers Cardiax

6. FACTORS THAT REGULATE MANDIBULAR MOVEMENTS Condylar guidance . Incisal guidance Influence of Opposing T ooth contacts. Neuromuscular factors .

7. CONDYLAR GUIDANCE ( Posterior determinant) Mandibular guidance generated by the condyle and the articular disc traversing the contour of the glenoid fossa-GPT. Slope of posterior wall of articular eminence-’s’ shaped.

8. Mediotrusive pathway is more steeper than protrusive pathway.---forms Fischer’s angle (5º). The angle formed b/w protrusive and nonworking side condylar path as viewed from sagittal direction Need not be transfered Hobo, S., & Takayama, H. (1994). A Study of the Fischer’s Angle. The Journal of Japan Gnathology, 15(1), 1–4. doi:10.14399/jacd1982.15.1 

9. CLINICAL SIGNIFICANCE: Shallow condylar guidance -Gliding movement has a more forward movement than downward movement Amount of separation is less Shorter cusps . Steep condylar guidance- --Condyle has a more downward movement than the forward movement Amount of mouth separation increases Sharper and taller cusps used.

10. INCISAL GUIDANCE(Anterior determinant) The influence of the contacting surfaces of the mandibular and maxillary anterior teeth during mandibular movements. Slope of the lingual surface of the upper anterior teeth,VO,HO determines the path along which the mandible moves during protrusive movement . It is usually expressed in degrees of angulation from horizontal by a line drawn in the sagittal plane between the incisal edges of upper and lower anterior teeth when closed in centric occlusion.

11. Greater horizontal overlap Less steep incisal guidance Greater vertical overlap More steep incisal guidance.

12. INFLUENCE OF OPPOSING TOOTH CONTACTS . In CD patients during centric & eccentric positions of mandibular movements The occlusal surfaces of teeth should meet evenly on both sides . During mandibular movements the inclined planes of the teeth should pass over one another smoothly and not disrupt the influences of condylar guidance posteriorly and incisal guidance of the teeth anteriorly . Then mandible is not deflected from its normal path of closure and the dentures not displaced from the residual ridge.

13. NEUROMUSCULAR SYSTEM ( Sessle ) Receptors located in PDL,Mandibular muscles,Mandibular ligaments. Proprioceptors Receptors in mucous membrane of oral cavity stimulated by touch, thermal- changes,pain /pressure. Mesencephalic- nucleus Sensory nucleus Thalamus Motor nucleus of trigeminal nerve Sensorimotor cortex Directly back to mandibular muscles (reflex arc) Voluntary changes in position of the mandible Involuntary movement of the mandible.

14. Clinical significance: Example of reflex involuntary movement: Involuntary movement of the mandible away from a source of pain,while one is making a jaw relation record. We can see a modification in the physiologic resting position of the mandible because of the soreness in the mouth from dentures.

15. Loss of propioceptors , locate d principally in periodontal ligaments, eliminates an important source of control in positioning of mandible for the edentulous patients. Compensated by constructions of complete denture with centric occlusion in harmony with centric relation. NEUROMUSCULAR ROLE

16. Impulses can also arise in motor cortex of the brain as a result of voluntary thought . Motor nucleus- -------  Muscles of mastication . CLINICAL SIGNIFICANCE: Patients can be trained voluntarily to make Posterior terminal hinge movements of the mandible Used to locate Transverse hinge axis. NEUROMUSCULAR ROLE

17. NEUROMUSCULAR ROLE Mastication is a programmed event residing in a ‘ chewing centre ’ located within the brain stem, probably in reticular formation of pons. ( CENTRAL PATTERN GENERATOR)

18. The cerebellum ensures a coordinated response from muscles during mandibular movements, by acting as a feedback control mechanism .. NEUROMUSCULAR ROLE

19. CLASSIFICATION

20. CLASSIFICATION OF MANDIBULAR MOVEMENTS . According to sharry : Based on Axis of movement: Rotation around the transverse axis Rotation around sagittal axis Rotation around vertical axis Based on direction of movement: Opening movements Closing movements Protrusive movements Lateral movements.

21. Based on extend of movements: Border movements Intra border movements. Based on habitual movements: Speech Mastication Degluttition Respiration CNS: Innate : Breathing & swallowing. Learned :Chewing and speech. Nonfunctional Movements: Bruxism

22. CLASSIFICATION OF MANDIBULAR MOVEMENTS Based on the dimensions involved in the movement : Rotation around the transverse axis Rotation around the sagittal axis. Rotation around the vertical axis. Based on the type of movement: Hinge movement Protrusive movement Retrusive movement Lateral movement Lateral rotation / Laterotrusion Lateral translation/Bennett movement Immediate side shift Precurrent side shift Progressive side shift

23. Based on the extend of movement : Border movements: Extreme movements in horizontal plane Extreme movements in sagittal plane Extreme movements in coronal plane. Envelope of motion. Intraborder movements: Functional movements: Chewing cycle Swallowing Yawning Speech Parafunctional movements : Clenching Bruxism Other habitual movements.

24. BASIC JAW POSITIONS Centric Relation The maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the antero-superior position against the slopes of articular eminences. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superiorly and anteriorly.

25. Centric Occlusion Occlusion of the teeth as the mandible closes in centric relation .It may or maynot coincide with the maximum intercuspal position. Maximum intercuspal position (Habitual/Acquired occlusion) The complete intercuspation of the opposing teeth independent of condylar position,some times reffered to as best fit of the teeth regardless of condylar position In 10% population CO coincides with MIP.

26. CR TO MIP SLIDE

27. BASED ON THE DIMENSION INVOLVED IN THE MOVEMENTS Rotation occurs around three axes: T ransverse , V ertical and S agittal , that move constantly during normal jaw function.

28. MOVEMENT ABOUT A TRANSVERSE AXIS, AS SEEN IN A MOUTH OPENING MOVEMENTS . During protrusive and mouth opening movements. Transverse axis varies during different phases of mouth opening movements. Initially it passes through head of the condyle---Hinge axis movement Later stages passes through mandibular foramen

29. MOVEMENT OCCURS AROUND A VERTICAL AXIS DURING LATERAL EXCURSION. Mandible moves towards right then vertical axis of rotation will pass through right condyle and vice versa.

30. THE MANDIBLE ALSO ROTATES AROUND A SAGITTAL AXIS WHEN ONE SIDE DROPS DOWN DURING LATERAL EXCURSION Condyle of the working side side moves upward and laterally Condyle on opposite side move downward and medially.

31. BASED ON THE TYPE OF MOVEMENTS Hinge movement Protrusive movement Retrusive movement Lateral movements

32. HINGE MOVEMENT Purely rotational movement of the joint Around a horizontal axis passing through right and left condyles called TERMINAL HINGE AXIS- --  MC Collum .

33. Hinge movement occurs when there is 10°-13° rotation of condyle in the glenoid fossa. Provides a jaw separation of 20-25mm in the incisal region. Occurs while crushing food & taking in food . Beyond 13° of rotation , Gliding movement starts ----then it is not a hinge movement Produced by Suprahyoid muscles & aided by gravity

34. PROTRUSIVE MOVEMENT Condyle rotate more than 13° in the fossa. Then mandible moves forwards and downwards. Transverse hinge axis passing through both condyles shifts to the level of the mandibular foramen .

35. Mandible slides forwards then mandibular and maxillary anterior teeth are in edge to edge relation,then protrusive movement is complete. Complete disocclusion of posterior teeth- ----- Christensen’s Phenomenon. Seen during incising and grasping food. Lateral pterygoid and suprahyoid muscles

36. RETRUSIVE MOVEMENT : Mandible is forcefully moved behind its centric relation. Temporalis, Digastric,Deeper fibers of masseter. 0.5mm movement, strained position. Not a common movement, patient cannot voluntarily reproduce it.

37. LATERAL MOVEMENTS Lateral rotation Lateral translation

38. LATERAL MOVEMENTS Mandible moves laterally (Side to side) ---Chewing foods. Lateral rotation Consider mandible move towards Left side The left condyle is called working condyle The right condyle is called Non-working condyle / Balancing condyle/Orbiting condyle.

39. Lateral rotation of mandible occurs around vertical axis passing through WSC The working side not limited by any anatomical structures other than temporomandibular ligament So working condyle can move in 5 directions in a cone of 60°. Laterotrusion Laterosurtrusion Laterodetrusion Lateroprotrusion Lateroretrusion The non working condyle – arcs Forward Downward and Medially .

40. LATERAL TRANSLATION / LATERAL SHIFT/ BENNETT MOVEMENT . Norman . G.Bennett in 1908 . The bodily lateral movement of the mandible resulting from the movements of the condyle along the lateral inclines along the mandibular fossae in lateral jaw movements. Shifts is common to both condyles but measured in nonworking side. 1-4mm shifts of mandible towards working side.(0.75mm)

41. BENNETT MOVEMENT IMMEDIATE SIDE SHIFT PRECURRENT SIDE SHIFT PROGRESSIVE SIDE SHIFT 3 ATTRIBUTES AMOUNT DIRECTION TIMING

42. BENNETT MOVEMENT CLASSIFICATION IMMEDIATE SIDE SHIFT : Mandible shifts before the forward movement of non –working condyle.

43. PRECURRENT SHIFT/ EARLY SIDE SHIFT : 75% of the shifts occurs with in the first 3mm of forward movement of non-working condyle.

44. PROGRESSIVE SIDE SHIFT/ BENNETT SIDE SHIFT: Mandible shifts linearly along with the forward movement of the nonworking condyle. Shift is gradual & linear.

45. The progressive side shift determines the value of bennett angle . Immediate Side Shift In mm Progressive Side Shift In degrees

46. BENNETT ANGLE: The angle formed by the sagittal plane and the path of advancing condyle during lateral mandibular movements. OR The angle formed between the path of the non-working condyle and the sagittal plane. Average value: 7.5°- 12.8° For hanau articulator , Bennet angle(L)=H/8+12 Programmed using lateral records

47. CLINICAL SIGNIFICANCE: Bennett movement and Bennett angle vs posterior restorations . More bennett movement : Cusp of posterior teeth should be shorter Occlusal fossae should be wider. Steeper the bennett angle Narrower the cusp Shallower the bennett angle Broader the cusp LATEROSUPERIOR MOVEMENT– Shorter cusp LATEROINFERIOR MOVEMENT- Longer cusp The more the immediate movement- -- the shorter the posterior teeth

48. BASED ON EXTEND OF MOVEMENTS Border movements Extreme movements in horizontal plane Extreme movements in sagittal plane Extreme movements in frontal /coronal plane Envelope of motion Intra border movements Functional Chewing Swallowing Speech Yawning Parafunctionl

49. EXTREME MOVEMENTS IN THE HORIZONTAL PLANE Diamond tracing Arrow point tracing formed using gothic arch tracers same pattern. . Left lateral border movements Continued left lateral border with protrusion Right lateral border movements Continued right lateral border with protrusion

50. Left lateral border movement Condyles in CR, Contraction of Right inferior lateral pterygoid Right condyle moves Anteriorly,Medially and Inferiorly. Left condyle in CR,Left inferior lateral pterygoid is relaxed Left lateral border movement

51. Continued left lateral border movement with protrusion Contraction of left lateral pterygoid & continued contraction right inferior pterygoid Left condyles moves Anteriorly and to Right Mandibular midline coincides with midline of face

52. Right lateral border movements Condyles in CR Contraction of left inferior lateral pterygoid Left condyle moves anteriorly,medially and Inferiorly Right lateral border movement

53. Continued right lateral movement with protrusion Contraction of rt. lateral pterygoid & continued contraction left inferior pterygoid Right condyles moves anteriorly and to left Mandibular midline coincides with midline of face

54. EXTREME MOVEMENTS IN SAGITTAL PLANE Beak tracing Posterior opening border Anterior opening border Superior contact border Functional Posterior and anterior opening border –Limited by ligaments and morphology of TMJ Superior contact border- --- Determined by the occlusal and incisal surfaces of teeth . Functional movements ---Neuromuscular system

55. Posterior Opening Border Movements :- 1 st STAGE 2 ND STAGE Condyles: terminal hinge P osition /CR Pure rotational movement Axis of rotation shifts to bodies of rami. Condyle begins to translate.

56. 1 st STAGE Opening range: 20-25mm The movements are the only repeatable hinge axis movement of mandible. 2 ND STAGE Condyles: anteriorly & inferiorly. Mandible: posteriorly & inferiorly. M a x opening : 40-60 mm.

57. Anterior Opening Border Movements:- Generated when closure accompanied by contraction of inferior lateral pterygoid. Not a pure hinge movement due to eccentricity.

58. Superior Contact Border Movements Throughout this entire border movement tooth contact is present. It depends on:- Amount of variation between centric relation and maximum intercuspation. Th e s t e e pnes s o f the cuspal i nclin e s o f the posterior teeth. Amou n t o f v erti c al a n d hori z o n t al o v erl a p of anterior teeth Lingual morphology of maxillary anterior teeth. General inter arch relationships of the teeth.

59. EXTREME MOVEMENTS IN SAGITTAL PLANE Clinical significance : Single restorations are constructed in harmony with MIP. Complete dentures are constructed with occlusion in harmony with centric relation.CR=CO=MIP At resting postion condyle move forward and downward and reach a position where minimum tonic contraction that is necessary to support mandible against force of gravity. This position is helpful for determining VD at Rest. Helps to establish vertical dimension of occlusion

60. EXTREME MOVEMENTS IN CORONAL PLANE CO, Centric occlusion MO, point of maximum opening of the jaws Rest, postural rest position. Shield Tracing

61. Left lateral superior movement

62. Left lateral opening movement

63. Right lateral superior border movement

64. Right lateral opening border movement

65. THE ENVELOPE OF MOTION . Combine border movements of all three planes. Posselt in 1952 Longest and widest superiorly and narrows down to MMO. Hence as jaw seperation increases space for movement decreases to zero at MMO

66. MAXIMUM MOVEMENTS- Opening : 50-60 mm Lateral : 10 to 12 mm Protrusive : 8 to 11 mm R etrusive range : 1 mm.

67. INTRABORDER MOVEMENTS Functional Movements:- Occur during functional activity of mandible. T ake place within border movements. Occur chiefly around centric.

68. EFFECT OF POSTURE ON FUNCTIONAL MOVEMENTS

69. Chewing movements: - MURPHY—SIX PHASES . Preparatory phase Food contact phase Crushing phase Phase of tooth contact Grinding phase Centric occlusion TEAR DROP TRACING

70. SPEECH Mandibular movement during speech is variable according to syllables used,accent,and speed. Definitive repeatable jaw writings are difficult to record during speech SWALLOWING During swallowing –mandible goes to CR Then a pause Movement to resting phase. Tongue helps to seal the palate so bolus will go posteriorly only. This movement of tongue helps to move mandible to CR position.

71. PARAFUNCTIONAL MOVEMENTS. DIURNAL ACTIVITY: Awake bruxism Clenching NOCTURNAL ACTIVITY During Non –REM sleep Oromandibular myoclonus Rhythmic masticatory muscle activity During REM sleep Tonic activity Oromandibular dystonia

72. REVIEW OF LITERATURE

73. Ferrario et al (1992) Int. J.Prosthodont Males have a significantly greater mean value of vertical rest position than females. There is no gender difference in mean value of mouth opening. Woelfel et al. (1957) J Prosthet Dent . They investigated the function of Ext. Pterygoid muscle during mandibular hinge axis opening by means of EMG. It was found that the electrical activity of external pterygoid muscle does not increase during the hinge opening movement. The suprahyoid muscles aided by the post. fibers of temporal muscle maintain the retruded position of the mandible.

74. Claudio Rodrigues,Marco Antonio. Kinesiographic study of mandibular movements during functional adapatation to complete dentures.Journal of applied oral science Dec 2003 Vol.11 ,No:4 Pattern of mandibular movement doesnot demonstrate significant changes between pre and post insertion stages of utilisation of complete dentures. Tupac (1978) J Prosthet Dent 136 dentulous were divided in 3 groups for the purpose of quantitative pantographic comparison of voluntary and induced Bennett movements. Conclusion was- Inducing Bennett movements has a greater effect on immediate side shift component than it has on the progressive side shift component. For older individuals the amount and direction of induced immediate side shift is greater than for younger patients.

75. Warren c,Riveria morales,A simplified technique to measure mandibular range of motion JPD 1996. Tongue blade is used to mark and measure maximum opening and eccentric movements. Low cost,convenience , Ease of use. More practical way to document range of motion than mandibular kinesograph .

76. Conclusion Knowledge of jaw movements is essential for successful treatment of patients. It is imperative to learn as much possible about jaw movement, in order to reproduce those aspects of its motion and is considered necessary for proper functioning of the occlusion either natural or artificial.

77. R E F E R ENCES Complete denture prosthodontics – 3 rd edition, by John J Sharry Prosthodontic treatment for edentulous patients- boucher -9 th edition. Syllabus of complete dentures-Charles.M.Heartwell-4 th edition Fundamentals of fixed prosthodontics – Shillingburg Management of Temporomandibular Disorders and Occlusion, 6th Edition – Jeffrey P Okeson Text book of prosthodontics Deepak nallaswamy-2 nd edition

78. Thank You