MUSCLES OF MASTICATION AND TEMPOROMANDIBULAR JOINT.pptx

ABOUT MUSCLLES OF MASTICATION AND TEMPOROMANDIBULAR JOINT AND ITS CLINICAL IMPICATIONS IN DENTISTRY

1. Previous seminar questions What is prenatal genetic counseling ? Prenatal genetic counselors work with individuals, couples, or families who have an increased chance of having a child with a birth defect or genetic condition . During pregnancy, if a baby is found to have a birth defect or genetic condition you may be referred to a prenatal genetic counselor. The counselor will help the expecting couple understand the medical information, what to expect, and how to prepare for the birth of a child with special needs, as well as discuss options such as pregnancy termination or adoption.

2. Cleft lip and palate management Cleft Lip and   Palate are common congenital deformities that often affect speech, hearing, and cosmesis ; and may at times lead to airway compromise  Surgical Techniques Surgical techniques are aimed to restore the normal anatomy of lip, nose, and face Normal or near normal anatomy promotes normal function, thereby encouraging normal growth and development of lip, nose, palate and facial skeleton

3. Timing of Surgery: Rule of tens – At least 10 weeks old Weighs at least 10 pounds Has Hb . Of 10 gm. Better results are obtained when the child is at least 3 months Cleft   Lip Two surgical techniques are used most widely in cleft lip surgery: Rotation-advancement technique Triangular flap technique It is first stage of two stage lip reconstruction

4. Cleft  Palate Several Techniques- Trend is towards less scarring and less tension on palate Scarring of palate may cause impaired mid- facial growth (alveolar arch collapse, mid face retrusion , malocclusion) Facial growth may be less affected if surgery is delayed until 18-24 months, but feeding, speech, socialization may suffer

5. MUSCLES OF MASTICATION Dr.Lakshmi J 1 ST MDS Dept of public health dentistry

6. Contents 1.Introduction 7.Primary muscles 2.Definition 8.Accessory muscles 3.Development 9.Mandibular movement and role played by muscles 4.Important facts about mastication 10.Masticatory muscle disorders 5.Features of masticatory muscles 11.Conclusion 6.Classification 12.Reference

7. Food is the main source of energy this energy is derived through the complicated process of digestion 1 st step of digestion is mastication Teeth ,jaws, muscles of jaws, tongue and the salivary glands aid in mastication INTRODUCTION

8. Rhythmic opposition and separation of jaws with the involvement of teeth,lips ,cheeks and tongue for chewing of food inorder to prepare it for swallowing and digestion Muscles of mastication are the group of muscles that helps in movement of mandible during chewing and speech.

9. They have a role in the equilibrium created within the mouth and control the opening and closing the mouth Four pairs of the muscle is the mandible make chewing movement possible These muscle along with accessory ones together are termed as muscle of mastication

10. DEFINITIONS MUSCLE an organ that by contraction produces movements of an animal ;a tissue composed of contractile cells or fibers that effect movement of an organ or part of the body MASTICATION is defined as the process of chewing food in preparation for swallowing and digestion

11. The muscular system develops from intra embryonic mesoderm from embryonic cells called myoblast Muscle of mastication are derived from 1 st brachial arch that is mandibular arch DEVELOPMENT

12. 5 th -6 th week Primitive cells form and differentiate Get oriented to site of origin and insertion 7 th week Mandibular arch mass enlarges Cell migrate to areas of formation of 4 major muscles of mastication Cell differentiation occurs before formation of facial arch 10 th week Muscle mass well organized Nerve masses get incorporated

13. There are 15 chew in a series from time of food entry until swallowing Average jaw opening during chewing- 16-20mm Average lateral displacement- between 3 and 5mm Duration of masticatory cycle-0.6-1sec Masticatory force – the average maximum sustainable biting force is 756N IMPORTANT FACTORS ABOUT MASTICATION

14. Shorter contraction time Incorporate more of muscle spindles to monitor their activity Do not have golgi tendon organs to monitor tension Do not get fatigued easily FEATURES OF MASTICATORY MUSCLE

15. Psychological stress increase the activity of jaw closing muscles Occlusal interferences –hypertonic synchronous muscle activity Closing movement is also determined by the height of the teeth

16. CLASSIFICATION ACCESSORY MUSCLES MUSCLES PRIMARY MUSCLES Masseter Temporalis Lateral pterygoid Medial pterygoid Suprahyoid Geniohyoid Stylohyoid Digastric mylohyoid Infrahyoid Omohyoid Thyrohyoid Sternohyoid sternothyroid

17. PRIMARY MUSCLES

18. MASSETER Quadrilateral muscle Covers lateral surface of ramus of mandible

19. ORIGIN INSERTION Superficial layer- from anterior 2/3 rd of lower border of zygomatic arch and adjacent zygomatic process( down backward 45 º) Lower part of lateral surface of ramus of mandible Middle layer- lower border of posterior 1/3 rd of zygomatic arch Center part of ramus of mandible Deep layer- deeper surface of zygomatic arch(vertically downward) Rest of ramus of mandible

20. ACTION Elevates mandible Superficial fibers- protrusion NERVE Massetric nerve (branch of anterior division of mandibular nerve)

21. PALPATION The patient   is asked to clench their teeth and, using both hands, the practitioner palpates the masseter muscles on both sides extra orally, making sure that the patient continues to clench during the procedure. Palpate the origin of the masseter bilaterally along the zygomatic arch and continue to palpate down the body of the mandible where the masseter is attached.

22. • Masseter muscle can be palpated both intraorally and extraorally • The masseter muscle is sometimes the target of plastic jaw reduction surgery. • The muscle that commonly undergoes Hypertrophy in Bruxism is Masseter • Because of the Multi pennate arrangement of fibers masseter is a very powerful muscle CLINICAL IMPORTANCE

23. TEMPORALIS Fan shaped muscles Fills the temporal fossa

24. ORIGIN INSERTION Temporalis fossa excluding zygomatic bone Temporal fascia Anterior fibers- runs vertically Middle fibers- obliquely Posterior fibers- horizontally Margins and deep surface of coronoid process Anterior border of ramus of mandible Converges and passes through gap deep to zygomatic arch

25. ACTION Elevates mandible Side to side grinding motion Posterior fibers retracts protrudes mandible NERVE 2 deep temporal branch from anterior division of mandibular nerve

26. PALPATION The muscle   is divided into three functional areas and therefore each area is independently palpated. To locate the muscle, have the patient clench. The anterior region is palpated above the zygomatic arch and anterior to the TMJ. The middle region is palpated directly above the TMJ and superior to the zygomatic arch. The posterior region is palpated above and behind the ear. Anterior Middle Posterior

27. CLINICAL IMPORTANCE   Sudden contraction of temporalis muscle will result in coronoid fracture, which is rare.

28. LATERAL PTERYGOID Short and conical Has upper and lower hea d

29. ORIGIN INSERTION Upper head(small)- infra temporal surface Crest of greater wing of sphenoid bone Lower head(larger)- lateral surface of lateral pterygoid plate(Medial to insertion ) Fibers runs backward and laterally and converge for insertion Upper head- pterygoid fovea of anterior surface of neck of maandible Lower head- anterior margin of articular disc and capsule of TMJ ( Posteriolateral and at higher level than origin)

30. ACTION Depress mandible to open mouth with suprahyoid Lateral and medial pterygoids protrudes mandible Right lateral pterygoid and right medial pterygoid turns chin to left side as part of grinding movements NERVE A branch from anterior division of mandiblar nerve

31. PALPATION Placing the forefinger, or the little finger, over the buccal area of the maxillary third molar region and exerting pressure in a posterior, superior, and medial direction behind the maxillary tuberosity .

32. MEDIAL PTERYGOID Qurdilateral muscle Have superfical and deep head

33. ORIGIN INSERTION Superical - tuberocity of maxilla Deep- medial surface of lateral pterygoid plate and adjoining process of palatine bone Runs downward , backward and laterally Roughened area on medial surface of angle and adjoing ramus of mandible Below and behind mandibular foramen and mylohyoid groove

34. ACTION Elevates mandible Protrudes mandible Right medial pterygoid +right lateral pterygoid = chin to left side NERVE Nerve to medial pterygoid ( branch of main trunk of manibular nerve

35. PALPATION

36. CLINICAL IMPORTANCE Medial Pterygoid muscle can be palpated only intraorally • Most commonly involved in MPDS • Trismus following inferior alveolar nerve block is mostly due to involvement of medial pterygoid muscle

37. ACCESSORY MUSCLES

38. SUPRAHYOID

39. MUSCLE ORIGIN INSERTION NERVE SUPPLY ACTIONS DIGASTRIC Anterior belly Posterior belly Digastric fossa Mastoid notch(temporal bone) Intermediate tendon Intermediate tendon N. To Mylohyoid Facial nerve Elevate hyoid Depress mandible 2. GENIOHYOID Inferior genial tubercle Hyoid bone (body-anterior surface) C1 through hypoglossal nerve Elevate hyoid Depress mandible 3. STYLOHYOID Styloid process Hyoid bone (junction of body and greater cornu ) Facial nerve Elevate hyoid 4. MYLOHYOID Mylohyoid line- mandible Hyoid bone- body N. to mylohyoid Elevate mandible Depress mandible Elevate floor of mandible

40. INFRAHYOID

41. MUSCLE ORIGIN INSERTION NERVE SUPPLY ACTIONS OMOHYOID Superior belly Inferior belly Intermediate tendon Superior border of scapula Hyoid bone Intermediate tendon C1-Ansa cervicalis(superior root Ansa cervicalis( C1-C3) Depress hyoid 2. STERNOHYOID Manubrium sterni (posterior surface) Hyoid bone (medial part of lower border) Ansa cervicalis Depress hyoid 3. STERNOTHYROID Manubrium sterni (posterior surface) Thyroid cartilage (oblique line) Ansa cervicalis Depress larynx 4. THYROHYOID Thyroid cartilage (oblique line) Hyoid bone-lower border of body and greater cornu Cervical spinal nerve(C1) via hypoglossal nerve Depress hyoid Elevate larynx

42. ELEVATORS RETRACTORS DEPRESSORS M edial Pterygoid L ateral Pterygoid M asseter (Superficial oblique fibres M asseter T emporalis M edial Pterygoid L at pterygoid M ylohyoid G eniohyoid D igastric T emporalis D igastric G eniohyoid PROTRUDES

43. : ELEVATION Prime Movers: (a) Masseter (b) Medial Pterygoid (c) Temporalis Antagonist: (a) Superior Lateral Pterygoid 2. DEPRESSION: Prime movers: (a)Inferior lateral pterygoid (b) Digastric Antagonist: (a) Elevator group muscles MANDIBULAR MOVEMENTS AND ROLE PLAYED BY MUSCLES

44. 3.PROTRUSION Prime Movers: (a) Inferior Lateral Pterygoid (b) Masseter (c)Medial Pterygoid Antagonist: (a) Digastric (b) Posterior Temporal 4. RETRUSION : Prime movers: (a) Posterior & Middle Temporal (b) Digastric Antagonist: (a) Inferior Lateral Pterygoid 5. LATERAL : Prime movers: (a) Working side of temporal muscle Antagonist: (a) Non working side of Pterygoid muscle

45. Some of the common masticatory muscle disorders involve: Trismus Bruxism Tetanus Congenital hyperplasia/ hypoplasia Hypermobility / hypo mobility of the muscle Muscle pains MPDS Myositis ossificans etc. Temporal tendonitis MASTICATORY MUSCLE DISORDER

46. Due to prolonged tetanic spasm of the jaw muscles by which normal opening of the mouth is restricted. Restricted jaw movements regardless of the etiology. CAUSES: TRISMUS Intracapsular Pericapsular Muscular Other Arthritis Condylar fracture Irradiation Dislocation Infection & inflammation TMJ dysfunction syndrome Tetanus Oral sub mucous fibrosis Systemic sclerosis Fractures

47. PROBLEMS: Eating issues Oral hygiene issues Swallowing issues Joint immobilization TREATMENT Removal of the cause Heat therapy Warm saline rinses NSAIDs Passive muscle stretching exercises

48. Bruxism is the clenching or grinding of the teeth when the individual is not chewing or swallowing It can occur as a brief rhythmic strong contractions of the jaw muscles during eccentric lateral jaw movements, or in maximum intercuspation , which is called clenching. CAUSES: Associated with stressful events Non stress related or hereditary BRUXISM

49. Bruxism may lead to: Tooth wear Fracture of the teeth or restoration Muscle hypertrophy TREATMENT Coronoplasty Maxillary stabilization appliance Increased muscle tension is directly related to stress activity during the day.

50.   Tetanus is a disease of the nervous system characterized by intense activity of motor neuron and resulting in severe muscle spasm Caused by exotoxins of gram positive bacillus, clostridium tetani . CLINICAL FEATURES : Pain and stiffness in the jaws and neck muscles ,with muscle rigidity producing trismus and dysphagia Rigidity of facial muscles Sometimes whole body becomes affected. TETANUS

51. TREATMENT: All patients should receive antimicrobial drugs Active and passive immunization. Surgical wound care Anticonvulsant if indicated

52. MYOFACIAL PAIN DYSFUNCTION SYNDROME Muscular disorders ( myofacial pain disorders) are the most common cause of TMJ pain associated with masticatory muscles. Common etiologies include: Patient with “high stress level” Poor habits including gum chewing, bruxism , hard candy chewing Poor dentition

53. TREATMENT: Its treatment includes 4 phases of therapy which includes muscle exercises and drugs involving NSAIDs and muscle relaxants. A bite appliance is also worn by the patient in the furthur stages to ‘splint’ the muscle movement .

54. CONGENITAL HYPOPLASIA / HYPERPLASIA   It occurs very rarely, and is more common in masseter and orbicularis oris . Its oral symptoms include enlargement or decreased size of the affected muscle, which may show an asymmetric facial pattern and stiffness in the temporo-mandibular joint. It may or may not be associated with hypermobility / hypo mobility of the muscles.

55. MUSCLE HYPERMOBILITY / HYPOMOBILITY This disorder involves extreme or diminished activity of the masticatory muscles. Its etiology includes various factors such as: Decreased/ increased threshold potential of neural activity. Parkinsonism Facial paralysis Nerve decompression Secondary involvement of systemic diseases.

56. The  masticatory muscles include a vital part of the orofacial structure and are important both functionally and structurally Precise movement of mandible by the musculature is required to move the teeth effectively acreoss each other during function The knowledge of the anatomy physiology and mechanism of these muscles are basic to understand the movements CONCLUSION

57. REFERENCES  Human anatomy by B.D. Chaurasia , 3rd ed. Human anatomy by dental students by M.K. Anand , 1st ed.  Burkits oral medicine diagnosis & treatment 10th edition Shafer'S Textbook Of Oral Pathology (6Th Edition) by sivapathasundharam

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