8-mandibular movement.power point presentation

Mandibles movements

1. Mandibular movement

2. Inrtoduction    Mandibular movements are complex in nature and are essential for all functions and parafunctions . The knowledge of mandibular movements is essential To understand various aspects of occlusion . To arrange artificial teeth, To select and adjust recording device and articulators.

3. All mandibular movement is either R otation or T ranslation

4.    In most of the movements of the mandible, the rotation and translation cannot be isolated Rotational centers for mandibular movements are three interrelated axes: transverse . vertical Sagittal

5.   Rotation   The movement of a rigid body in which parts move in circular paths with their the centers on a fixed line called the axis of rotation Rotational movement of he mandible take place in the lower compartment of the TMJ between the superior surface of the condyle and the inferior surface of the articular disk.    

6. Transverse Horizontal ( hinge) axis : is the imaginary line connecting the rotational center of the condyles . & around which the mandible rotate in opening & closing

7.    Mandibular Hinge Position the position of the mandible in relation to the maxilla at which opening and closing movement can be made on the hinge axis.

8.   .The maximum range of terminal hinge rotation averages about 12° and creates a range of 18 to 25 mm of inter incisal opening . The transverse horizontal( hinge) axis can be located clinically by the kinematic face-bow when the mandible is guided through its most retruded opening and closing.

9. Translation That motion of a rigid body in which a straight line passing through any two points always remains parallel to its initial position. The motion may be described as a sliding or gliding motion .

10. Translatory Movement The motion of a body at any instant when all points within the body are moving at the same velocity and in the same direction . Translation, translatory or gliding movements of the mandible take place in the upper compartment of the TMJ where the condyles and the articular disk move as a unit.

11. Mandibular movement 1-opening & closing movement 2-protrosive & protrusive movement 3-lateral movement

12. This movement starts from the intercuspal position to the maximum opening position. At the beginning of the opening movement, there is a rotation in the lower compartment of the TMJ, with further opening a gliding movement occurs in the upper compartment. As soon as the rotation ends , the condyles begins to translate ,moving forward & downward with the arc of opening changing & the mandible opening further till the maximum opening position

13. The condyle rotate in its place in the terminal hinge position . Upon rotation of the condyles , the mandible can open till 2-2.5 cm. & the teeth discluded

14. Pure rotation occurs only till the condyles start to translate moving out of its centricity The condyles usually start to translate immediately when the teeth are separated from the intercuspal position.

15. The first few millimeters of opening can be considered as a hinge movement. This movement is mainly produced by gravity and the contraction of the anterior belly of the digastric muscle

16. For the closing movement , the mandible moves from the maximum opening position with a reverse movement back to the intercuspal position. Closing is brought about by the contraction of the masseter and the medial pterygoid muscles.

17. 2. Protrusive & Retrusive Movement: a/Protrusive movement: The condyles together with their articular discs move as one unit downwards and forwards along the glenoid fossa and the articular eminence. Protrusive movements are brought about by the contraction of the lateral pterygoid muscles on each side.

18. The path travelled by the condyles in the protrusive movement is termed the sagittal condylar path. It forms an angle with the horizontal plane (occlusal plane) termed the sagittal condylar angle It varies in individuals and also in the same individual from the left to the right sides. It ranges between 30°-40°.

19. When the mandible moves forward to an edge to edge position a separation occurs distally between the distal arches or occlusion rims. This distal separation of teeth is the result of the forward and downward glide of the condyle on the articular eminence. This phenomenon is called Christensen phenomenon

20. b/ Retrusive movements: The retrusive movement of the mandible takes place by similar movements as the protrusive ones, but in the reverse direction i.e. upward and backward along the same inclination. Starting from the intercuspal position, this movement is brought about by the contraction of the temporalis muscles

21. In natural dentition the mandible can move backwards to a slight extent. This most retruded position of the mandible is a strained position. It can be obtained by active conscious contraction of the retractors of the mandible (posterior fibers of the temporalis ) or passively by the operator pressing on the symphysis menti when the patient is relaxed completely

22. 3. Lateral Movement: The mandible is capable of moving towards both the right & lift sides . The side towards which the movement occurs is called the working or chewing or bolus side. The opposite side is called the non-working or balancing side.

23. Bennett movement: is the lateral bodily movement of the rotating(working) condyle , with medial movement of the translating(non-working) condyle

24. the amount of Bennett movement is determined by the medial wall of the glenoid fossa on the (non-working) side. The non-working condyle moves medially till it is in contact with the medial wall . Bennett angle: is formed between the mid- sagittal plane & the medial wall of the glenoid fossa or we can say the condyle of the non-working side (7-8 degrees)

25. In summary protrusive movements are used in the grasping and incising of food, while the right and left lateral excursions are used for the reduction of fibrous, as well as, other types of bulky food. A combination of all these movements appears to be the most effective in the trituration of food.

26. Border Movement The mandibular movements are limited by: 1/ligaments 2/the articular surfaces of the TMJ 3/the morphology and alignment of the teeth. mandibular movement at the limits dictated by anatomic structures, as viewed in a given plane is reproducible and called border movements.

27. Functional movement Occur during functional activity of the mandible Are confined within the Border Movements Begin and end in the maximum intercuspation position (ICP)

28.   Envelope of Motion The three dimensional space circumscribed by mandibular border movements within which all unstrained mandibular movement occurs.

29. it was a combination of border movements in all 3 planes: sagittal , horizontal & vertical

30. The envelope differs from person to person but it has the same characteristic shape The superior surface of the envelope is determined by the tooth contacts The other borders are primarily determined by the TMJ anatomy and the ligaments

31. Questions

32.    BordL’r and iniraborft ” Movemenls Border refers to the bouidarY of a surface m av imply the limiting line. Border Positions ,,• tile mandible can by defined as 'the extreme ro1. tions of the mandibular in any. direction in whic . it moves “. Lines drawn between these pOsitzorLc

33.   Screen clipping taken: 11/17/2015, 4:15 PM     till scribe a geometrie shape called “the envelop or the envelop ments “. The border 2ositions are limited by the mudcles , ligaments.   uf motion   of   nerves,   bones,   mandibular move-   teeth when present,   and

34.   Screen clipping taken: 11/17/2015, 7:52 PM     o enilig Mo vein en This type of movement relaxa tion ? of the elevator muscles pterygoid , temporalis and masseter muscles and activity of the lateral pterygoid muscles on both sides aided by active infra-mandibular muscles ( supraand infrahyoid muscles) which may function to stab iliie ? the hyoid bone during swalh \ wminfg , speech

35. Tuesday, November 17, 2015 7:54 PM   Screen clipping taken: 11/17/2015, 7:54 PM     At th . bLginninl , oF mandit the condyles of’ the mandible ro tnrnsverse axis for about 1 - condyles start translation dowir along the anterior walls of the gisi ‘ oii The center of rotation during this norn ia mo ment is located near the lingulae . The maximw opening range for a normal healthy subject is 35 to 55 mm. Deviation from this range is an indicat ion? of pathological condition such as trisnmus or subluxation .

36.   Screen clipping taken: 11/17/2015, 8:00 PM     (7ocill a .410 vein en t This type of movement is affected b non of the elevator muscles and relaxati lateral pterygoid and infra-mandibular Closing movement around stationary rotatirm . condyles is assisted by contraction of the poster ior ? fibers of the temporalis muscle and the su hyoid muscles

37.    Mandibular transltion occurs in either the sagittal plane along the articular eminence ( sagittal condylar path) or the coronal plane along the lateral inclines of the glenoid ( fossa rlateral condylar path ). In most cases the translatory movement is a combined translation in both horizontal and coronal planes. As the mandible is one bone, the lateral translation of the condyles results in a mandibular shift this lateral mandibular shift was first described by Bennett and is know after him as the Bennett movement ( laterotmusion ).

38.    Bennett Movement ( Laterotrusion ) Condylar movenent on the working side in the horizontal plane. This term may be used in combination with terms describing condylar movement in other planes

39.   The interplay among various muscles acting on the temporomandibular joint are much more fundamental to an understanding of mandibular movements than are the ligaments or the control of the joint itself. Muscles of mastication are the primary movers of the mandible, but movement is the result of concerted action of these muscles and infra-mandibular and posterior cervical muscles.