Group 5 assignment 7
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- 1.GROUP 5 ASSIGNMENT
2. OBASANYA Adedotun Augustine-DEN/2007/051 (CHAIRMAN)
OGUNLOLA OmowumiAbosede-DEN/2007/057 (SECRETARY)
DADA Babatunde- DEN/2007/036
OKUNOLA Ibukunoluwa Esther- DEN/2007/063
IWEGBU Samuel Enere -DEN/2007/046
3. JAW MOVEMENTS AND POSITIONS
MANDIBLE It is the largest and strongest bone of the face. It develops from the first pharyngeal arch. It has a horse - shoe body which lodges the teeth, and a pair of rami which projects upwards from the posterior ends of the body and provide attachments to muscles
To study mandibular movement one should have knowledge about anatomy of temporomandibular joint, function and neurophysiology of masticatory system and mechanism of mandibular movement.
The temporomandibular joint, or TMJ, connects the lower jaw called the mandible, to the temporal bone at the side of the head. There are two temporomandibularjoints, one on each side of the jaw.
Since TMJ are flexible, the jaw can move smoothly up and down and side to side, allowing us to talk, chew and yawn.
Muscles attached to, and surrounding the joint, control its position and movement
6. Temporomandibular joint
When opening the mouth, the rounded ends of the lower jaw joint, called condyle, glide along the joint socket of the temporal bone The condyle slide back to their original position when we close our mouth
7. Articular disc divides the joint cavity into upper and lower cavities
8. Temporomandibular joint
Protrusion or protraction, Retraction, Depression, Elevation
Muscles involved are known as muscles of mastication. Muscles of mastication are temporalis, masseter, lateral pterygoid (L Pt), Medial pterygoid( M Pt)
9. Temporomandibular joint
Protraction is brought about by lateral pterygoid assisted by medial pterygoid
10. Retraction by posterior fibers of temporalis
Elevation-temporalis , masseter and medial pterygoid
11. Lateral chewing movements-alternately protruding and retracting the mandible on each side with a certain amount of rotation
12. Determination of mandibular movements
Factors thatdeterminemandibular movements are:
13. Condylar guidance(posterior determinant)
It can be defined as the mandibular guidance generated by the condyle and articular disc traversing the contour of the glenoid fossa.
The condylemoves along the glenoid fossa during mandibular movements . Hence, the surface of the glenoid fossa determines the path of movement of the condyle.
The slope of the glenoid fossa is a S-bend, hence the condyle moves along a S-shaped path.
14. Incisal Guidance(anterior determinant)
It is defined as the influence of the contacting surfaces of the mandibular and the maxillary teeth during mandibular movements.
During protrusion, the incisal edge of the lower anteriors slide along the slope of the lingual surface of the upper anterior teeth before reaching edge-to-edgecontact.
The incisal guidance is absent in a completely edentulous patient. It is reproduced in the complete denture by arbitrarily setting the anteriors using a standard incisal guide value and modifying to suit the patient during aesthetic anterior try-in.
15. Neuromuscular factors
The muscles of mastication are the most important determinants of mandibular movements.
Many neurological disorder like parkinsonism produce muscle dysfunction
Each muscle has a specific action on the mandible
The movement of the mandible in any direction is predominantly controlled by one particular muscle and is coordinated by the remaining.
When there is hypertrophy or dysfunction of one group of muscles, the movement of the mandible is un-coordinated and asymmetrical.
16. MECHANISM OF MANDIBULAR MOVEMENT
17. Mandibular movement occurs as a complex series of interrelated three dimensional rotation and transitional activities. It is determined by combined and simultaneous activities of both temporomandibular joints. Although the TMJ is cannot function entirely independent of each other, they also rarely function with identical concurrent movement.
18. Types of mandibular movement
A.Based on the dimension involve in the movement.
B.Based on the type of movement
C. Based on the extent of movement
Mandibular movement occur as a complex series of interrelated 3-D ROTATIONAL and TRANSLATION activities.
20. 1) Rotational movement
- This is the movement of a body about its axis.
21. In the masticatory system, rotation occurs when the mouth opens and closes around a fixed point or axis within the condyles. 22. In TMJ, rotation occurs as the movement within the superior surface of the condyle and the inferior surface of articular disc. 23. Rotational movement of mandible can occur In 3 ways(plane):horizontal , vertical/ frontal andsaggital.