Stomatognathic system .pptx Salzmann’s defined, the interdependence of form and function of teeth, jaws relationship, temporomandibular articulation, craniofacial conformation and dental occlusion.

Salzmann’s defined, the interdependence of form and function of teeth, jaws relationship, temporomandibular articulation, craniofacial conformation and dental occlusion.

1. STOMATOGNATHIC SYSTEM Presented by: D hanvi D esai (Part 1 PG) Department of Orthodontics and Dentofacial O rthopaedics

2. CONTENTS Introduction Functional osteology Myology Functions of Stomatognathic system

3. Stomatognathic System Salzmann’s defined, the interdependence of form and function of teeth, jaws relationship, temporomandibular articulation, craniofacial conformation and dental occlusion.

4. FUNCTIONAL OSTEOLOGY FFUNCTIONAL OSTEOLFUNCTIONAL OSTEOLOGYOGY UNCTIONAL OSTEOLOGY FUNCTIONAL OSTEOLOGY

5. TRAJECTORIAL THEORY OF BONE FORMATION   1867 ANATOMIST MEYER AND MATHEMATICIAN CULMANN . Alignment of bony trabeculae in the spongiosa follows definite principles. Lines of orientation of the bony trabeculae correspond to pathways of maximal pressure and tension. Many of these trajectories cross at right angle to resist functional stresses.

6. LAW OF ORTHOGONALITY Julius Wolff in 1870 Trabecular alignment was primarily due to functional forces. Changes in intensity and direction of these forces produce change in internal architecture and external form of bone.

7. Law of transformation of bone   According to Roux, Stresses of tension or pressure on bone stimulate bone formation

8. Now, it is established that endochondral and membranous bones react differently to forces Trajectories need not pass at right angles to each other, even their course may be wavy Muscles have a great influence over bones and may even change their shape Increased functions increases bone density (Osteosclerosis) Decreased function decreases bone density (Osteoporosis )

9. Stress Trajectories Benninghoff - study of the architecture of cranial and facial skeleton, and their stress trajectories Lines pass through both the compact and spongy bone Obey no individual bone limits but rather demands of functional forces

10. Stress trajectories to absorb functional forces in middle face and cranium The canine pillar The zygomatic pillar The pterygoid pillar

11. Stress trajectories in the mandible

12. MYOLOGY To propel the skeleton man has –

13. Elasticity Elasticity of the body is related to Length Cross section Force exerted Nature of the body The extent of elasticity is dependent upon the nature of the material involved.

14. Contractility Contractility is the ability of a muscle to shorten its length under innervational impulse. Muscle is first stimulated by electric action potential, causing a contraction Energy for the muscle is provided by the break down of ATP

15. Contraction ISOMETRIC ISOTONIC Muscle is resisting an external Actual shortening force without any actual shortening

16. Strength of muscle contraction Open mouth Postural resting position Occlusion position Overclosure

17. Principles of muscle physiology These are like guiding principles or “laws”. All or None Law Muscle tonus Resting length Stretch or myotatic, reflexes Reciprocal innervation and inhibition

18. SHERRINGTON has pointed out that individual fibers have no variable contraction status, but are rather relaxed or going into maximum contraction by virtue of adequate stimulus – “ ALL OR NONE LAW ”.

19. MUSCLE TONUS State of slight constant tension Characteristic of all healthy muscle Basis of reflex posture Eg. Minimal contraction of antigravity muscles to maintain standing posture

20. RESTING LENGTH Constant and predeterminable relationship Permits maintenance of postural relations and dynamic equilibrium by contraction of the minimal number of fibers

21. STRETCH OR MYOTATIC REFLEX Reflex contraction of a healthy muscle which results from a pull on its tendon RECIPROCAL INNERVATION & INHIBITION Inhibition of the tonus or contractility of the muscle may be brought about by excitation of its antagonist

22. THE BUCCINATOR MECHANISM

23. Lip, tongue and cheek balancing forces on the teeth and supporting structures The molding pressure on the dental arch exerted by the contiguous musculature

24. TONGUE The extrinsic, suspensory muscles attach the tongue to various osseous structures. The hyoglossus – hyoid bone The styloglossus – styloid process The Genioglossus – mandible The palatoglossus – palatine aponeurosis.

25. Muscles of Tongue Intrinsic Muscles Actions Superior longitudinal Shortens the tongue makes its dorsum concave Inferior longitudinal Shortens the tongue makes its dorsum convex Transverse Makes the tongue narrow and elongated Vertical Makes the tongue broad and flattened

26. Extrinsic muscles Actions Genioglossus Protrudes the tongue Hyoglossus Depresses the tongue Styloglossus Retracts the tongue Palatoglossus Elevates the tongue

27. Nerve supply of Tongue

28. The tongue has versatile functional possibilities as it is anchored at only one end. This freedom permits the tongue to deform the dental arches when function is abnormal.

29. Abnormal tongue posture Proclination of anterior teeth Anterior open bite Posterior open bite in lateral tongue thrust Posterior crossbite

30. FUNCTIONAL MOVEMENTS An analysis of the precarious balance that the head maintains on the vertebral column illustrates the constant demand for activity in holding the head erect.

31. Muscle Activity Muscles primarily responsible for mandibular functional movements 1. Anterior and posterior fibers of temporalis 2. Lateral pterygoid 3. Anterior, middle & posterior components of masseter 4. Suprahyoid 5. Infrahyoid

32. Opening movement Gravity and the primary contraction of lateral pterygoid muscle Stabilizing and adjusting activity is by suprahyoid and infrahyoid group, in geniohyoid, mylohyoid and digastric muscles Controlled relaxation- Temporal, masseter, medial pterygoid muscles Hyoid bone- Moves downward and backward

33. Closing movement Bilateral activity of masseter and temporalis muscles, assisted by medial pterygoid muscles. Hyoid bone - moves upward and forward. Controlled relaxation- Lateral pterygoid

34. Protrusion Lateral and medial pterygoid muscle contract in conjunction with controlled stabilizing relaxation of the opening muscles.

35. Retrusion Contraction of the posterior fibers of the temporalis muscle along with geniohyoid, digastric and mylohyoid muscles Hyoid bone – Moves posteriorly

36. Working bite Established by lateral movement Initiated by lateral pterygoid muscle – temporalis muscle. Magnitude of contraction Working side > balancing side.

37. Bennett movement In the lateral shift of the mandible the articular disk moves toward the side of the working bite. This known as “ Bennett movement ”. Condyle on Working side – laterally and rotates. Balancing side – downward and forward.

38. Bennett Angle Angle formed between sagittal plane and condylar path on balancing side during lateral movements L = H/8 + 12 Range from 2° to 44°

39. POSITIONS OF MANDIBLE Sagittal plane positions of the mandible with respect to maxilla and cranium –

40. POSTURAL RESTING POSITION Earliest postural position Non functional mandible Altered by body shape and posture, sleep, age, occlusal changes such as attrition, muscle diseases or spasm

41. CENTRIC RELATION Unstrained, neutral position of mandible with anterosuperior surfaces of mandibular condyle in contact with concavities of the articular disk CENTRIC OCCLUSION Unstrained, static position with maximal contact of inclined planes of opposing teeth Premature contacts, loss of teeth, overeruption of teeth, overextension of artificial restorations

42. MOST PROTRUDED POSITION Most variable position Inclination of the condylar path is more important than actual protrusive position Dislocation- Fatigue syndrome

43. HABITUAL RESTING POSITION Habitual resting position may not be the same as physiologic postural position (Class II, Division 2 malocclusion)

44. HABITUAL OCCLUSAL RELATION Normal occlusion – Centric occlusion and habitual occlusion should be same Susceptible to functional aberrations, improper restorations, tooth loss Asynchronous activity of the closing muscles

45. Functions of the Stomatognathic System Mastication Deglutition Respiration Speech

46. Mastication Defined as the reduction of food in size, changing in consistency, mixing it with saliva and forming into a bolus suitable for swallowing Suckling – Unlearned or automatic reflex Rhythmic caving in of cheeks, bobbing of the hyoid bone, snake like movement of tongue, anterior mandibular thrust, sphincter-like activity of the lips and actual nodding movement of the head

47. Infant learns to take solid food Less activity of lips and mandibular thrust Learns to use lips to keep the food from being forced out during peristaltic-like action Ingested food mixed with saliva by tongue function Bolus takes up saliva it is forced between gum pads

48. Rhythmic action of muscles mashes the bolus against hard palate Mandible is depressed by gravity to permit bolus of food to interpose between teeth or gum pads After bolus is accommodated, mandible is forcibly closed, by temporal and masseter muscle

49. Chewing pattern in adult and child According to Moyers, the jaw muscles begin to learn mastication process when maxillary and mandibular incisors touch one another First or earlier chewing pattern – poorly developed

50. Child moves the jaw first laterally on opening and then masticatory cycle is performed Adult first opens straight down, moves the jaw laterally and then brings about teeth contact

51. Murphy’s Six Strokes of Mastication (Fletcher) 1. The Preparatory phase: Ingested food is positioned by the tongue inside the oral cavity. Mandible moves toward chewing side. 2. Food contact: Temporary hesitation in movement. Interpreted to be a pause triggered by sensory receptors concerning the apparent viscosity of food. 3 . The Crushing phase: Starts with high velocity then slows as food is crushed and packed. Display equal and synchronous activity on both sides.

52. 4. Tooth contact: Change in direction of chewing. All reflex adjustments of the musculature for tooth contact are completed in crushing phase. There is reduced muscular activity in masticator muscles, when this phase is reached 5. The Grinding phase: The outputs from periodontal ligament receptors reflexly control jaw closing muscles to ensure tooth slides into correct intercuspal position to grind the food into a paste. 6. Centric occlusion: Movement of teeth comes to a definite stop from which the preparatory phase of next stroke begins.

53. Deglutition a ) Infantile (visceral) swallow: Moyers listed the features of infantile swallow as follows: 1. Jaws are apart with the tongue interposed between the gum pads. 2. Mandible is stabilized by the contraction of muscles of facial muscles and by the interposed tongue. 3. Swallowing is guided and controlled by the sensory interchange between the lips and tongue

54. The gum pads are not usually in contact With liquid foods a “Clucking” is frequently heard Peristaltic muscle activity steers the liquid or bolus of food back into pharynx Food propelled by superior, middle & inferior pharyngeal constrictors, past the epiglottis into esophagus Epiglottis closes off the pharynx as its posterior portion are forced backward against superior constrictor ring

55. b) Mature (somatic) swallow: By 18 months of age, the mature swallow characteristics are seen

56. Phases of Deglutition by Fletcher 1) The Preparatory phase Starts as soon as liquids are taken or bolus has been masticated Swallow preparatory position on dorsum of tongue Oral cavity is sealed by lip and tongue

57. 2) The Oral phase Soft palate moves upward Tongue drops downward and backward Larynx and hyoid bone move upward This creates smooth path for bolus as it is pushed from the oral cavity by tongue Oral cavity is stabilized by muscles of mastication

58. 3) The Pharyngeal phase Begins as the bolus passes through fauces Pharyngeal tube is raised upward and nasopharynx is sealed off by closure of soft palate against posterior pharyneal wall Hyoid bone and base of tongue move forward

59. 4 ) The Esophageal phase Commences as food passes through cricopharyngeal sphincter As peristaltic movement carries food through esophagus , the hyoid bone, palate, tongue return to original position

60. Normal and Abnormal Swallowing

61. Respiration Physiologic respiration is the process by which multicellular living organisms capture and excrete the gaseous fuel and waste of cellular respiration The mandibular and tongue posture are major determinants of respiration. 25 weeks of intrauterine life. At this stage the lungs do not inflate Mandible moves downward and tongue also moves downward and then forward from the posterior pharyngeal wall to establish the airway

62. The column arrangement of tongue, hyoid, and larynx is held forward- for patency of the airway in the pharynx and the laryngeal vestibule Also held upward - with the tongue in approximation to the palate, so airway is in continuity with the nose, rather than the mouth

63. Maintainance of patent airway: In nose and oral cavity – Bony skeleton and posture of tongue In pharynx – Tone of muscles of tongue, soft palate and pharyngeal walls Development of respiratory spaces and maintenance of oral and pharyngeal airway space contribute to the growth of orofacial bones according to functional matrix hypothesis

64. Nasal airway function has been implicated as an etiologic factor in dentofacial development 1) Existence of a relationship between mouth breathing and facial form- Altered normal air currents and pressures causing impaired development of these structures 2) Compression theory ( Harvold , Linder-Aaronson et al) – Oral respiration disrupts the muscle forces exerted by the tongue, cheeks, and lips upon the maxillary arch 3) Denies a significant relationship between facial morphology and mode of breathing

65. Hyoid Bone Only bone without bony articulation Arises from cartilages of second and third branchial arches Suspended between cervical vertebrae and mandible Hyoid bone position plays an essential and active role in achieving postural balance and patency of the pharyngeal airway.

66. Enlarged tonsils – Caudally positioned hyoid bone with respect to mandibular plane Increased tongue size – Inferior and anterior movement Inferior and anterior - Class I skeletal pattern More inferior and posterior - Class II skeletal pattern More anterior and superior - Class III skeletal pattern S. Mortazavi et al. Hy oid bone position in different facial skeletal patterns. Journal of Clin Exp dent. 2018 Apr; 10(4): e346-e351.

67. Relationship between hyoid bone position and pharyngeal airway dimension in skeletal malocclusions Airway dimension is significantly narrower when location of the hyoid bone more posterior and inferior in Class II patients The more anterior the hyoid bone and the larger the pharyngeal airway dimension

68. Speech Learned activity. Low placement of larynx in human beings which enables the human vocal tract to achieve optimal resonance to produce different sounds

69. Neurophysiology Speech production begins in the motor area The cranial nerves involved in speech are Trigeminal (jaw movements and craniofacial sensation) Facial (circumoral muscle movement) Vagus (pharyngeal and laryngeal muscles) Hypoglossal (movement of tongue)

70. Mechanism of speech production Lungs: fill with air Contraction of rib cage forces air from the lungs into the trachea Trachea (windpipe): conveys air to the vocal tract Vocal tract consists of: pharynx, mouth, nose

71. Four functional subsystems interacting in the production of speech: 1. Respiration: provides the means by which larynx generates speech and voice. 2. Phonation: involved in sound production 3. Resonance: give the characteristic quality to the voice. The resonating structures are the air sinuses; organ surfaces; cavities such as the pharynx, oral cavity, and nasal cavity; and chest wall. 4. Articulation: for producing a variety of speech sounds, articulators are used.

72. Graber TM. Orthodontics: principles and practice. 3rd edition. WB Saunders company, Philadelphia 1988. TM Graber. The “three M’s”: Muscles, malformation, and malocclusion. AJO-DO 1963;418-50. Robert E Moyers. Handbook of orthodontics. 4th edition. Year Book Medical Publishers, Chicago 1988 Shridhar Premkumar. Textbook of craniofacial growth. 2 nd edition. 2011 B D Chaurasia’s . Human Anatomy. 7 th edition. 2016 REFERENCES

73. Graber, Vanarsdall , Vig . Orthodontics- Current Principles and Techniques. 6 th edition. 2017 Profitt W.R-Contemporary Orthodontics. 6 th edition. 2019.

74. Thank You