Introduction and Review of Masticatory System

1. Introductionand Review of Masticatory System โดย ผศ.ทพ.ดร.สิทธิชัย วนจันทรรักษ์

2. From DOCC 381 • Concept • Instruments and technique • Morphology of occlusion • Anatomy of mastication system • Mandibular movement • Neurophysiology of mastication • Sign and symptom of TMD • Occlusal splint

3. Introduction to DOCC 582 • Aetiology and Epidermiology of TMD • Clinical assessment of masticatory system • Diagnosis and Classification of TMD • Oral parafunction • Trauma from occlusion • Management of TMD problem • Interocclusal appliances

4. Occlusion also Includes • Biological evolution • Development • Histology • Anatomy • Biomechanics • Physiology (Neurophysiology) • Adaptation • Pathology • Behaviour sciences • Clinical diagnosis • Therapy

5. Definition (Jablonski, 1982) The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system The relationship between all the components of the masticatory system in normal function, dysfunction, and parafunction, including the morphological and functional features of contacting surfaces of opposing teeth and restorations, occlusal trauma and dysfunction, neuromuscular physiology, the TMJ and muscle function, swallowing and mastication, psychological status, and the diagnosis, prevention, and treatment of functional disorders of the masticatory system

6. Objectives and Goals • The subject of occlusion serves as a natural interface between certain of the biologic and behavioural sciences and the clinical sciences. • The subject of occlusion is, in the view of many, the medium that brings all branches of dentistry together (Ricketts, 1969)

7. The Masticatory System A dynamic biomechanical musculoskeletal system

8. Components of the Mastication • Dentitions • Periodontal supporting tissues • Maxilla and Mandible • Temporomandibular Joint • Mandibular musculature • Muscles of lips, cheeks, and tongue • Involving soft tissue • Supplying innervation and vasculation

9. 1 2 4 3 5 1 2 4 3 5 10 13 16 19 27 29 8 Primary Dentition Maxillary teeth Mandibular teeth Months

10. 6 1 2 4 5 3 7 8 6 1 2 3 4 5 7 8 8 10 12 20 6 Permanent Dentition Maxillary teeth Mandibular teeth Years

11. Loss of Teeth Causes Occlusal Disharmony • Early loss of deciduous teeth without space retaining appliances • Loss of mandibular first molar • lingual and mesial tipping of mandibular 2nd and 3rd molar • Loss vertical dimension • Changing in masticatory habit and muscle tonicity

12. Periodontal Supporting Tissues • Cementum • Periodontal ligament • Supporting bone Usually, periodontium is protected against injury by neuromuscular reflexes

13. Problems to Periodontium • Periodontal trauma • pattern of mastication • Loss of teeth • loss of periodontal support • Faulty restoration • Abnormal occlusal force; bruxism, clenching

14. Temporomandibular Joint (TMJ) A complex giniglymoarthrodial (hinge and glide) articulation with limited capability of diarthrosis (free movement)

15. Histology of TMJ Area

16. Temporomandibular Joint (TMJ) • Composed of • Condyle • Mandibular fossa • Articular capsule • Synovial tissue • Articular disc • Ligaments

17. Mandibular Condyle • Modified barrel shape approx. 20 x 10 mm (ML x AP) • Perpendicular to the ascending ramus of mandible • Dense cortical bone covered with dense fibrous connective tissue with irregular cartilage like cell

18. Mandibular Fossa • Dense cortical bony surface of temporal bone • Posterior to articular eminence • Posterior nonarticular fossa is formed by tempanic plate • Thin at the roof of the fossa and tympanic plate

19. Articular Capsule and Disk

20. Articular Capsule • Ligamentous capsule surrounds the joint • Attached to the neck of the condyle and around the border of the articular surface of the temporal bone • anterolateral aspect of the capsule may thicken form the Temporomandibular ligamentfunction as stabilising structure

21. Articular Capsule • Consist of • internal synovial layer • outer fibrous layer containing veins, nerves, and collagen fibres. • Innervation of capsule disk arises from CN V; auriculotemporal and masseteric nerves • Venous plexus at posterior aspect

22. Synovial tissue • Synovial cell and connective tissue covering the lower and upper-joint spaces • Synovial fluid, a proteoglycan-hyaluronic acid complex acts as a lubricant and may participated in nutritional and metabolic interchange for central part.

23. Articular Disk (Meniscus) • Biconcave oval structure interposed between the condyle and the temporal bone • 1 mm in the middle and 2-3 mm at periphery • Dense collagenous connective tissue • Centre area is a vascular, hyaine and devoid of nerve

24. Articular Disk (Meniscus) • Fuse to a strong ligament at lateral side connect to the neck of the condyle • The other borders are attached to capsule ligaments or synovial membranes separate between two joint spaces.

25. TMJ Ligaments

26. Ligaments • Temporomandibular ligament • extend from base of zygomatic process of the temporal bone downward and oblique to the neck of the condyle

27. Ligaments • Stylomandibular ligament • From styloid process and runs downward and forward to attach broadly on the inner aspect of the angle of mandible

28. Ligaments • Sphenomandibular ligament • arising from the angular spine of sphenoid bone and petrotympanic fissure, ending at lingula of mandible

29. Functions of Ligaments • Accessory ligaments may limit border movements of the mandible • Fibrous capsule and TM ligament may limit of extreme lateral movements in wide opening of mandible

30. Masticatory Muscles • Masseter muscle • Temporalis muscle • Medial pterygoid muscle • Lateral pterygoid muscle

31. Masster muscle • Superficial layer • O : lower border of malar bone, Zygomatic arch & zygomatic process of maxilla • R : Downward and Backward • I : Angle of mandible and inferior half of the lateral side of mandible

32. Masster muscle • Deep layer • O : Internal surface of zygomatic arch • R : Downward (vertical) • I : Ramus of mandible and base of coronoid process • 50 degree between 2 layers

33. Temporalis muscle • 3 bundles • Anterior bundle (vertical fibre) • Action: Mandible elevator (Close jaws), crushing and chewing at C.O. • Inaction: Mandible depression (except Max. Opening and Opening against resistance)

34. Temporalis muscle • Posterior bundle (Horizontal bundle) Action: Mand. retraction and positioner Inaction: Mand. depression and protrusion • Intermediate bundle Action: Protrisive movement • Nerve supply Ant. and Post. deep temporal nerve

35. Med. Pterygoid muscle Rectangular shape at medial surface of ramus, synergistic with masseter muscle O : Pterygoid fossa and medial surf. of the lateral pterygoid plate I : Inf. + Post. border of ramus and angle of mand. R : Downward and Backward N : Medial Pterygoid nerve

36. Lat. Pterygoid muscle • Superior head O: Wing of sphenoid and infratemporal crest R: Downward and Backward • Inferior head O: Lateral surf. of lateral pterygoid plate R: Upward and backward

37. Lat. Pterygoid muscle Insertion of superior and inferior heads • Ant. portion of the condylar neck (pterygoid fovea) • Ant. surface of the articular capsule • Ant. Border of the disk Function • Open the jaws, protrude and lateral movement with moving disk forward

38. Lat. Pterygoid muscle • Superior head Synergistic with elevator group of muscle for closing and clenching • Inferior head Synergistic with suprahyoid group of muscle for opening jaw • Nerve supply Lateral pterygoid nerve

39. Non Masticatory Muscle • Digastric muscle • Mylohyoid muscle • Geniohyoid muscle • Orbicularis Oris

40. Non Masticatory Muscle

41. Types of Mandibular Movement • Rotational movement • Horizontal axis of rotation • Frontal (vertical) axis of rotation • Sagittal axis of rotation • Translational movement

42. Rotational Movement • Around the horizontal axis (hinge axis)

43. Rotational Movement • Around the frontal (vertical) axis

44. Rotational Movement • Around the sagittal axis

45. Translational movement

46. Sagittal Plane Border Movement

47. Sagittal Plane Border Movement • Posterior open border • Anterior open border • Superior contact border • Functional movements

48. Horizontal Plane Border Movement • Left lateral border • Continued left lateral border with protrusion • Right lateral border • Continued right lateral border with protrusion • Functional movements

49. Horizontal Plane Border Movement • Continued right lateral border with protrusion

50. Horizontal Plane Border Movement • Functional movements