Mandibular movements and the envelope of motion

Mandibular moment and the envelope of motion that provides the clear idea of the movement of the mandible in horizontal vertical and sagittal surface. The clear mind ser of the movement can be achieved with help of this. It plays a major role in describe the treatment plan for the patient especially in for cases

1. MANDIBULAR MOVEMENTS Presented by Dr. Anjali Hukkeri 1

2. Table of contents SKELETAL COMPONENTS MUSCLES OF MASTICATION LIGAMENTS 01 05 04 02 06 03 INTRODUCTION METHODS TO RECORD MANDIBULAR MOVEMENTS REVIEW OF LITERATURE ANATOMY Conclusions MECHANICS AND BORDER MOVEMENTS SIGNIFICANCE OF MANDIBULAR MOVEMENTS 2

3. INTRODUCTION 01 3

4. 4 Introduction Mandibular movement occurs as a complex series of interrelated three-dimensional rotational and translational activities. It is determined by the combined and simultaneous activities of both temporomandibular joints (TMJs). Perry 1957, small occlusal disharmonies on the natural dentition can cause the muscle- joint syndrome so often seen.

5. 5 Introduction Normally , the mandible moves in a habitual manner to accomplish speech, mastication, deglutition, respiration, sucking, etc. Among the functions of masticatory systems, breathing and swallowing are innate; chewing and speech are learned.

6. ANATOMY OF MASTICATORY SYSTEM 02 6

7. 7 SKELETAL COMPONENTS The skeletal components of the human head are the skull and mandible. The skull is composed of several bones connected together by fissures. The major components are the temporal bone, the frontal bone, the parietal bone, the sphenoid bone, the occipital bone, the zygomatic bone, the nasal bone, and the maxilla. The three major skeletal components that make up the masticatory system are the maxilla and mandible, which support the teeth and the temporal bone, which supports the mandible at its articulation with the cranium.

8. 8 MAXILLA There are two maxillary bones, which are fused together at the midpalatal suture . Superiorly to form the floor of the nasal cavity . Inferiorly, the maxillary bones form the palate and the alveolar ridges

9. 9 2. MANDIBLE The mandible is a U-shaped bone that supports the lower teeth and makes up the lower facial skeleton. No bony attachments to skull. The condyle is the portion of the mandible that articulates with the cranium, around which movement occurs.

10. 10 2. MANDIBLE The total mediolateral length of the condyle is between 18 and 23 mm, and the anteroposterior width is between 8 and 10 mm. The posterior articulating surface is greater than the anterior surface.

11. 11 3. TEMPORAL BONE The mandibular condyle articulates at the base of the cranium with the squamous portion of the temporal bone. This portion of the temporal bone is made up of a concave mandibular fossa, in which the condyle is situated. ALSO- Articular or Glenoid fossa Immediately anterior to the fossa is a convex bony prominence called the Articular eminence .

12. 12 3. TEMPORAL BONE The degree of convexity of the articular eminence is highly variable; steepness of this surface dictates the pathway of the condyle when the mandible is positioned anteriorly. The posterior roof of the mandibular fossa - thin, area of the temporal bone is not designed to sustain heavy forces. The articular eminence, consists of thick dense bone and is more likely to tolerate such forces .

13. 13 TEMPOROMANDIBULAR JOINT The area where the mandible articulates with the temporal bone of the cranium is called the temporomandibular joint (TMJ). Complex joints Ginglymoid joint- hinging movement in one plane Same time- Arthrodial joint- gliding movements Ginglymoarthrodial joint Compound joint- requires the presence of at least three bones - Condyle of mandible, Squamous part of temporal and Functionally non osseous – Articular disc

14. 14 Articular disc Functionally serves as non osseous bone for complex movements. Dense fibrous connective tissue. No blood vessels and nerve supply except periphery. Sagittal plane- 3 region acc to thickness Central area is thinnest – intermediate zone Thicker- anterior - posterior

15. 15 From an anterior view, the disc is generally thicker medially than laterally, which corresponds to the increased space between the condyle and the articular fossa toward the medial of the joint. The precise shape of the disc is determined by the morphology of the condyle and mandibular fossa.

16. 16 Articular disc attachments- Posterior- Retrodiscal tissue- Connective tissue Superiorly – lamina of connective tissue- Superior retrodiscal lamina lower border of the retro discal tissues is the inferior retrodiscal lamina. The remaining body of the retrodiscal tissue is attached posteriorly to a large venous plexus, which fills with blood as the condyle moves forward

17. 17 T he articular disc is attached to the capsular ligament not only anteriorly and posteriorly but also medially and laterally. divides the joint into two distinct cavities. The upper or superior cavity is bordered by the mandibular fossa and the superior surface of the disc. The lower or inferior cavity is bordered by the mandibular condyle and the inferior surface of the disc. The internal surfaces of the cavities are surrounded by specialized endothelial cells that form a synovial lining.

18. 18 Synovial fluid- 2 purposes- Acts as a medium for providing metabolic requirements to these tissues. Serves as a lubricant between articular surfaces during function. Lubrication – 2 mechanisms Boundary lubrication Weeping lubrication

19. 19 Ligaments Important role in protecting structures Dense collagenous connective tissue fibres Particular in length, do not stretch Do not enter actively into joint function - act as passive restraining devices to limit and restrict border movements.

20. Ligaments - Functional Ligaments Spenomandibular ligaments Capsular ligament Collateral ligaments Accessary Ligaments Temporomandibular ligaments Stylomandibular ligaments 20

21. 21 Collateral (discal) ligament Origin -medial and lateral borders of the articular disc Insertion - poles of the condyle. Commonly called the discal ligaments Function- restrict movement of the disc away from the condyle. In other words, they allow the disc to move passively with the condyle as it glides anteriorly and posteriorly. Anterior view

22. 22 Capsular ligament Entire TMJ is surrounded and encompassed by the capsular ligament . Attachment- 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. Acts to resist any medial, lateral, or inferior forces that tend to separate or dislocate the articular surfaces. Lateral view

23. 23 Temporomandibular ligament The lateral aspect of the capsular ligament is reinforced by strong, tight fibers that make up the lateral ligament or the temporomandibular ligament. Composed of 2 parts- outer oblique portion and an inner horizontal portion The oblique portion of the TM ligament resists excessive dropping of the condyle, therefore limiting the extent of mouth opening. The outer oblique portion of the TM ligament functions to resist the impingement on the vital submandibular and retromandibular structures of the neck. The inner horizontal portion of the TM ligament limits posterior movement of the condyle and disc.

24. 24 Spenomandibular ligament An accessory ligaments It arises from the spine of the sphenoid bone and extends downward to a small bony prominence on the medial surface of the ramus of the mandible called the lingula. It does not have any significant limiting effects on mandibular movement. 

25. 25 Stylomandibular ligament It arises from the styloid process and extends. downward and forward to the angle and posterior border of the ramus of the mandible. It becomes taut when the mandible is protruded, but is most relaxed when the mandible is opened. The stylomandibular ligament therefore limits excessive protrusive movements of the mandible.

26. 26 Skull- the skeletan of the head is called skull includes mandible Several bones form Cranium Skull= cranium Skull/ cranium = Calvaria + facial skeleton Calvaria- brain box- upper part of cranium holds brain

27. 27 Zygomatic process T hree  processes  (protrusions) from other  bones  of the  skull  which each  articulate  with the  zygomatic bone . Zygomatic process of frontal bone   from the  frontal bone Zygomatic process of maxilla  from the  maxilla Zygomatic process of temporal bone   from the  temporal bone

28. 28

29. 29 Muscles of Mastication

30. 30 Masseter Rectangular muscle Origin- zygomatic arch and extends downward to the lateral aspect of the lower border of the ramus of the mandible Two portions or heads: the superficial portion consists of fibers that run downward and slightly backward; The deep portion consists of fibers that run in a predominantly vertical direction. Contracts- mandible elevated- teeth contact provides the force necessary to chew efficiently

31. 31 Temporalis The temporalis is a large, fan-shaped muscle that originates from the temporal fossa and the lateral surface of the skull. It can be divided into three distinct areas according to fiber direction and ultimate function. When the temporal muscle contracts, it elevates the mandible, and the teeth are brought into contact.

32. 32 Medial Pterygoid The medial (internal) pterygoid originates from the pterygoid fossa and extends downward, backward, and outward to insert along the medial surface of the mandibular angle. When its fibers contract, the mandible is elevated and the teeth are brought into contact. This muscle is also active in protruding the mandible. Unilateral contraction will bring about a mediotrusive movement of the mandible.

33. 33 Lateral Pterygoid Two distinct portions or bellies: an inferior and a superior. Inferior Lateral Pterygoid: The inferior lateral pterygoid originates at the outer surface of the lateral pterygoid plate and extends backward, upward, and outward to its insertion primarily on the neck of the condyle. The right and left - contract simultaneously, Condyles- pulled forward down the articular eminences and the mandible is protruded. Unilateral contraction - mediotrusive movement- condyle- lateral movement of the mandible to the opposite side

34. 34 Superior Lateral Pterygoid: Smaller than the inferior Origin- infra temporal surface of the greater sphenoid wing, extending almost horizontally, backward. Insertion- articular capsule, the disc, and the neck of the condyle Active during the power stroke and when the teeth are held together.

35. 35 Digastric Two portions or bellies- 1 . The posterior belly - mastoid notch, just medial to the mastoid process; its fibers run forward, downward, and inward to the intermediate tendon attached to the hyoid bone. 2 . The anterior belly - fossa on the lingual surface of the mandible, just above the lower border and close to the mid line; and its fibers extend downward and backward to insert at the same intermediate tendon as does the posterior belly.

36. 36 Digastric When the right and left digastrics contract and the hyoid bone is fixed by the suprahyoid and infrahyoid muscles, the mandible is depressed and pulled backward and the teeth are brought out of contact. When the mandible is stabilized the digastric muscles with the suprahyoid and infrahyoid muscles elevate the hyoid bone, which is a necessary function for swallowing

37. 37 Mechanics of Mandibular Movement Two types of movement occur in the TMJ: Rotational Translational

38. 38 Rotational movement Dorland’s Medical Dictionary defines rotation as “the process of turning around an axis: movement of a body about its axis.” In the TMJ, rotation occurs as movement within the inferior cavity of the joint. Movement between the superior surface of the condyle and the inferior surface of the articular disc. HORIZONTAL, VERTICAL(FRONTAL) AND SAGITTAL PLANES. Axis- rotation around a point.

39. 39

40. 40 Horizontal Axis of rotation Mandibular movement around the horizontal axis is an opening and closing motion. It is referred to as a hinge movement, and the horizontal axis around which it occurs is therefore referred to as the hinge axis “pure”’ rotational movement

41. 41 When the condyles are in their most superior position in the articular fossae and the mouth is purely rotated open, the axis around which movement occurs is called the terminal hinge axis .

42. 42 Frontal( Vertical) Axis of rotation Mandibular movement around the frontal axis occurs when one condyle moves anteriorly out of the terminal hinge position with the vertical axis of the opposite condyle remaining in the terminal hinge position.

43. 43 Sagittal axis of rotation Mandibular movement around the sagittal axis occurs when one condyle moves inferiorly while the other remains in the terminal hinge position Because the ligaments and musculature of the TMJ prevent an inferior displacement of the condyle (dis location), this type of isolated movement does not occur naturally.

44. 44 Translational movement Translation can be defined as a movement in which every point of the moving object has simultaneously the same velocity and direction. In the masticatory system, it occurs when the mandible moves forward, as in protrusion. Translation occurs within the superior cavity of the joint between the superior surface of the articular disc and the inferior surface of the articular fossa (i.e., between the disc–condyle com plex and the articular fossa).

45. 45 Sagittal Plane Border and Functional Movements Mandibular motion viewed in the sagittal plane can be seen to have four distinct movement components: 1. Posterior opening border 2. Anterior opening border 3. Superior contact border 4. Functional.

46. 46 Posterior Opening Border Movements This pure rotational opening can occur until the anterior teeth are some 20 to 25 mm apart. 1 st Stage 20- 25mm 2 nd Stage 40- 60mm

47. 47 Anterior Opening Border Movements

48. 48 Superior Contact Border Movements Throughout this entire movement, tooth contact is present. Its precise delineation depends on- (1) the amount of variation between CR and maximum intercuspation (2) the steepness of the cuspal inclines of the posterior teeth (3) the amount of vertical and horizontal overlap of the anterior teeth (4) the lingual morphology of the maxillary anterior teeth (5) the general interarch relationships of the teeth.

49. 49 1 3 2 4

50. 50 5 6

51. 51 Functional Movements Functional movements occur during functional activity of the mandible. They usually take place within the border movements and therefore are considered free movements. Most functional activities require maximum intercuspation and therefore typically begin at and below the ICP. When the mandible is at rest, it is found to be located approximately 2 to 4 mm below the ICP- called the clinical rest position.

52. 52 Postural Effects on Functional Movement-

53. 53 Horizontal Plane Border and Functional Movements A rhomboid-shaped pattern can be seen that has four distinct movement components

54. 54 Horizontal Plane Border and Functional Movements Components: Left lateral border Continued left lateral border with protrusion Right lateral border Continued right lateral border with protrusion.

55. 55 Left Lateral Border Movements- Rotating Condyle Orbiting Condyle

56. 56 Continued Left Lateral Border Movements With Protrusion-

57. 57 Right Lateral Border Movements

58. 58 Continued Right Lateral Border Movements With Protrusion

59. 59 Functional Movements

60. 60 Frontal (Vertical) Border and Functional Movements Functional component: 1.Left lateral superior border 2. Left lateral opening border 3. Right lateral superior border 4. Right lateral opening border.

61. 61 Left Lateral Superior Border Movements

62. 62 Left Lateral Opening Border Movements

63. 63 Right Lateral Superior Border Movements

64. 64 Right Lateral Opening Border Movements

65. 65 Functional Movements

66. 66 Envelope of Motion By combining mandibular border movements in the three planes (sagittal, horizontal, and frontal), a three-dimensional envelope of motion can be produced It represents the maximum range of movement of the mandible. Reference position from where fundamental movements of mandible occur. Posselt’s envelop of motion

67. 67 Bennett Movement Dr. Normal Bennett, 1908 Synonym- LATEROTRUSION/ MANDIBULAR LATERAL TRANSLATION Bodily side shift of the whole mandible Average shift- 0.75mm working condyle Cause- contraction of external Pterygoid muscle- origin located medially to insertion and anterior

68. 68 During a lateral excursion the orbiting condyle moves downward, forward, and inward in the mandibular fossa around axes located in the opposite (rotating) condyle. two factors: (1)morphology of the medial wall of the mandibular fossa (2) inner horizontal portion of the temporomandibular ligament (TM), which attaches to the lateral pole of the rotating condyle.

69. 69 Immediate side shift- Mediolateral movement the translatory portion of lateral movement in which the nonworking-side condyle appears to move essentially in a straight line and medially, on a 2D tracing, as it leaves the centric relation position. GPT 9

70. 70 Progressive side shift- The translatory portion of mandibular movement as viewed in a specific body plane that occurs at a rate or amount that is directly proportional to the forward movement of the nonworking-side condyle. GPT 9 Begins there after and continues with major direction in anterior

71. 71 Bennett Angle Angle formed between the sagittal plane and the average path of the advancing nonworking-side condyle as viewed in the horizontal plane during lateral mandibular movements (GPT-4) Mean – 16 degree

72. 72 Fischer’s Angle Angle formed by the intersection of the protrusive and nonworking-side condylar paths as viewed in the sagittal plane when a recording of mandibular movement is made by using a device located lateral to the temporomandibular joints. Avg 5-10 degree

73. 73 Significance of Mandibular Movements Mastication Deglutition Speech Respiration Developing Tooth Forms For Dental Restorations, Understanding Occlusion, Arranging Artificial Teeth, Treating TMJ Disturbances, Preserving Periodontal Health the designing, selection and adjustment of articulators.

74. 74 MASTICATION- Communication of food preparatory to deglutition. Mechanical, chemical, bacteriologic and enzymatic. Tooth contacts- most in chewing strokes- natural dentition, full denture patients DEGLUTITION- Innate function Oral; Pharyngeal; Esophageal During deglutition mandible is stabilized against maxilla by contraction of masseter and temporal muscles. Results in contact of upper and lower teeth

75. 75 SPEECH RESPIRATION Mouth – secondary to nasal cavity Swollen nasal mucous membrane- mouth - primary respiratory passage

76. 76 Methods to record Mandibular Movements Methods using Mechanical Device Photographic Method Roentgenographic Method Electronic and Telemetric Method Magnetometry The Mandibular Kinesiograph (MKG ) Opto-electronic Methods Pantograph s Stereographics Axiography Cadiax Compact Computerized Analysis of Mandibular Movement Electromagnetic Articulography (EMA)

77. Thankyou 77