masticatory apparatus for prosthodontics.pptx

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1. The Mastication Apparatus

2. Mastication Apparatus The Mastication apparatus consist of a centre core or a framework consisting of the bones, the temporomandibular joint and the muscles of mastication.

3. MAXILLA It is the second largest bone of the face It forms the upper jaw with the fellow of the opposite side It also contributes to the formation of Floor of the nose and the orbit Roof of the mouth Lateral wall of the nose Pterigopalatine and infratemporal fossae Pterigomaxillary and infraorbital fissures

4. Anatomy of the maxilla The anatomy of the maxilla has two main parts: Body(pyramidal shape) Anterior surface Posterior surface Orbital surface Nasal surface Processes Zygomatic Frontal Alveolar Palatine

5. Maxillary Sinus Large pyramidal cavity with its apex directed laterally towards the zygomatic process Base is towards the lateral wall of the nose In articulated skull it is reduced by Above Uncinate process of ethmoid Desending part of lacrimal bone Below: inferior nasal concha Behind: perpendicular plate of palatine It opens into the middle meatus of the nose usually by two openings one of which is closed by mucous membrane in living state Occasionally there are projections in the maxillary sinus from roof to anterior wall

6. Processes Zygomatic: it is rough and pyramidal Front:it is contineous with the anterior surface of body Behind(concave):in continuity of the posterior surface Above: articulates with zygomatic bone Below(arched border) which anterior and posterior surface of the body

7. Frontal Process: Lateral Surface: Vertical ridge (Lacrimal crest) Groove for the lacrimal sac Medial surface: It is rough and uneven and articulates with the ethmoid and also closes the anterior ethmoidal sinus below ethmoidal crest Upper end: Articulates with the frontal bone Anterior border with the nasal bone Posterior border with the lacrimal bone

8. Alveolar processes: It has thick arched border behind and contains sockets to receive roots of teeth which vary in size and depth Canine deepest Molar widest and subdivided into 3 minor sockets by septae Incisors and premolars single Occasionally incisors are divided into 2 sockes

9. Palatine Process: Thick strong horizontal Inferior surface is concave and presents numerous foramina for passage of nutrient vessels and contains depressions for lodgement of glands Groove for grater palatine Vessels and nerves Incisive fossa leads into the incisive canal Sometimes anterior and posterior incisive foramen for long sphenopalatine nerve which communicates with the greater palatine nerve Upper surface: forms the floor of the nasal cavity Lateral Border fuses with rest of the bone Posterior border fuses with the horizontal plate of the palatine

10. Arterial supply

11. Maxillary Artery

12. Veinous drainage

13. Nerve Supply

14. Lymphatics

15. Age changes in Maxilla

16. MANDIBLE Largest and strongest bone of the face Curved horizontal body; convex forwards It has two rami which project upward from posterior end of the body The body is horse shoe shaped

17. Arterial Supply of Maxilla and Mandible

18. Nerve supply of Mandible

19. Veinous drainage of Mandible

20. P r ocesses: Con d y l ar Co r onoid Mandibular canal

21. Age changes in mandible

22. The Temporomandibular joints It is a joint present between head of mandible and the articular fossa and articular eminance of the temporal bone Type of joint : It is a condylar variety of synovial joint The joint cavity of TMJ is divided by fibro- cartilagenous disc into 2 compartments

23. Bony framework of joint Proximal : Articular fossa and the articular eminance of the mandible Distal side: Head of mandible Articular surfaces: The anterior eminance is formed by the root of zygoma and the articular surface is formed by the smooth area of tht mandibular fossa of the temporal bone The distal articular surface is also a smootharea forned by the head of the mandible.

24. The ligaments of TMJ True ligament Capsular ligament Temporomandibular ligament Accessory ligament Stylomandibular ligament Sphenomandibular ligament

25. True ligaments Capsular ligament: It is like a fibrous sac over the joint cavity. It is attached above to the articular surface of TMJ and on the other side to the neck of the mandible It covers the joint cavity very loosely It is covered by the synovial membrane

26. Temporomandibular ligament: this ligament is the thickening of the lateral part of the capsular ligament It runs posterio-inferiorly and is attached above to the articular surface and below to the ramus of mandible and the posterio-lateral aspect of the mandible

27. Accessory ligament It provides additional support to the TMJ Stylomandibular ligament: This ligament is formed by the thickening of the deep cervical fascia. It is attached above to the styloid process and below to the angle of mandible and lateral border of ramus of mandible This ligament helps to seperate the parotid gland and the submandibular gland

28. Spheno-mandibular ligament; This ligament is attached above to the spine of the sphenoid bone and below to the lingula on the mandible. This ligament is innervated by various nerves and vessels Embryologically it is the un-ossified intermediate part of the Meckel’s cartilage of the 1 st branchial arch

29. Interior of the joint The bones forming the joint cavity are covered by fibrous cartilage rather than the hyaline cartilage The absence of hyaline cartilage makes it an atypical type of synovial joint

30. The articular disc The articular disc divides the joint into two compartments, the upper and the lower compartment Articular disc is a fibro-cartilagenous disc, it is thickened in the periphery and thin in the center The vascularity is also more in the periphery

31. Relations of the joint Anteriorly : fibres of the muscles of lateral pterigoid Posteriorly : part of the parotid gland Medially : spheno mandibular ligament Laterally : parotid gland

32. The supply of the gland Arterial supply Superficial temporal artery Maxillary artery Veinous drainage Superficial temporal vein Retromandibular vein Lymphatics: It drains into the superficial and deep parotid lymph nodes and deep cervical nodes.

33. Movements of the TMJ The principle movements of the joint are: » Elevation » Depression » Protraction » Retraction » Side to side movements Various muscles are involved in these movements, collectively known as muscles of mastication.

34. Elevation Messeter Anterior fibres of temporalis Medial Pterigoid Depression Lateral pterigoid muscle Anterior belly of digastric, mylohyoid and geniohyoid also assist Protraction Retraction Masseter, Medial pterigoid and lateral pterigoid Deep fibres of masseter Posterior fibres of temporalis Side to side movements It is caused by alternate contraction and relaxation of Medial and lateral pterigoid

35. Muscles of mastication There are 4 muslces involved in mastication Masseter Temporalis Medial pterigoid Lateral pterigoid

36. Masseter Origin: it arises from 2 heads Superficial hear arises from the lower border of the anterior 2/3 rd of the zygomatic arch Deep head arises from the whol length of the zygomatic arch and lower border of th posterior 1/3 rd of the zygomatic arch. Insertion: The two heads unite and gets inserted into the whole length of the outer surface of the ramus and angle of mandible N. Supply: Massetric nerve and a branch of anterior division of the Mandibular nerve Actions: Elevation of mandible Protrusion of the mandible

37. T emp o r alis Origin: whole length of the temporal fossa, the fascia covering of the temporalis and from the inferior temporal line The anterior fibres are vertical, posterior are horizontal and middle fibres are oblique Insertion: all the fibres converge to form a thick tendon which passes deep to the zygomatic arch and is inserted into the medial surface, the apex, the anterior and the posterior border of the coronoid process and anterior border of ramus of mandible upto the last molar tooth. Nerve supply: Deep temporal nerve which arises from the anterior division of the mandibular nerve Actions: Anterior fibres are strong elevators of the mandible Posterior fibres retract the mandible

38. Lateral Pterigoid Origin: It also arises from two heads The upper/superior head originates on the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone, lower/inferior head on the lateral surface of the lateral pterigoid plate Insertion: Inferior head inserts onto the neck of condyloid process of the mandible; upper/superior head inserts onto the articular disc and fibrous capsule of the temporomandibular joint N. Supply: The mandibular branch of the fifth cranial nerve, the trigeminal nerve, specifically the lateral pterigoid nerve, innervates the lateral pterygoid muscle. Actions: Unlike the other three muscles of mastication, the lateral pterygoid is the only muscle of mastication that assists in depressing the mandible (opening the jaw).

39. Superior head of lateral pterigoid Inferior head of lateral pterigoid

40. Medial pterigoid Origin: The bulk of the muscle arises as a deep head from just above the medial surface of the lateral pterigoid plate. The smaller, superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone. Insertion: Its fibers pass downward, lateral, and posterior, and are inserted, by a strong tendinous lamina, into the lower and back part of the medial surface of the ramus and angle of the mandible N. Supply: Like all other muscles of mastication the medial pterygoid is innervated by the anterior root (motor root) of the mandibular branch of the trigeminal nerve (V). Actions: It contributes to following functions: Elevation of the mandible (closes the jaw) Minor contribution to protrusion of the mandible Assistance in mastication Excursion of the mandible; contralateral excursion occurs with unilateral contraction

41. Medial pterigoid insertion origin