Anatomy of stomatognathic system dental courses in hyderabad /certified fixed orthodontic courses by Indian dental academy

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  • An articular disc is biconcave, like a red blood cell. It isn’t uniform, however, as different areas have different relative thicknesses. From the side view, the anterior and posterior borders are both fairly thick, with the posterior a little thicker than the anterior. The centre (the intermediate zone) is quite a bit thinner- it’s in this centre region that the condyle rests- the disc like a hat that sits on the head of the condyle.
    From a frontal view, the medial part of the disc is thicker than the lateral- the disc is thickest in the same areas where the articulating surface of the condyle is greatest- posterior and medial.
  • The TMJ doesn’t consist of just the condyle, disc, and mandibular fossa- these are surrounded and aided in their functions by a number of other tissues and structures to make up the whole TMJ.
  • The articular disc is attached at its medial and lateral borders to the condyle by the 2 collateral (discal) ligaments. These help keep the disc positioned on the condyle by limiting the directions in which the disc can move- they allow it to rotate anteriorly and posteriorly on the head of the condyle, but limit side-to-side movement.
  • The capsular ligament keeps the TMJ in place and the articular surfaces together- it resists forces that would pull the joint away from it’s location. It also has sensory and proprioceptive functions, and produces and contains the synovial fluid found in the joint cavities, keeping it from leaking away.
  • The outer oblique portion of the TM ligament is a heavier, thickened and reinforced area of the capsular ligament, running from the neck of the condyle to the articular eminence and posterior part of the zygomatic process. It acts to prevent excessive opening of the mouth, and also influences the nature of the opening movement, causing a change from a rotational movement of the joint to a translational movement as it reaches it’s full length.
    The enclosed, inner horizontal portion runs from the articular eminence and posterior part of the zygomatic process to the lateral pole of the condyle and posterior part of the articular disc. It has a different function- it limits posterior movement of the condyle and disc, preventing damage to the vulnerable tissues posterior to the TMJ.
  • The TMJ is a compound joint that functions like two joints in one, and can be thought of as 2 separate joints working together. Each joint cavity is responsible for a different type of joint movement.
  • Synovial fluid performs two important functions- it helps to lubricate the articular surfaces, reducing friction, and also performs metabolic exchange for the cells of the disc and articular surfaces of the condyle and mandibular fossa, which havefew to no blood vessels. The synovial fluid allows oxygen and nutrients to diffuse in and wastes to diffuse out.
    The synovial fluid performs these functions by two different mechanisms- boundary lubrication and weeping lubrication.
    Boundary lubrication results from the synovial fluid moving around from one area to another inside the joint cavity as the joint itself moves (eg. like water in a washing machine, or transmission fluid in an automatic transmission). This is the primary method of fluid function.
    Weeping lubrication occurs when synovial fluid is absorbed and released from the articular surfaces as a result of pressure from forces created by joint function- the fluid squishes in and out of the articular surface cells due to compressive forces (as happens when the teeth are clenched). This is a secondary mechanism, and is a little bit similar to water or soap being squeezed out from a sponge.
  • Muscle fibers are grouped together into functional units called motor units. Each motor unit consists of a number of muscle fibers that are all innervated by 1motor neuron.
    The number of fibers in a motor unit varies according to the function of the muscle in question. Muscles with motor units having fewer fibers controlled by a single motor neuron have greater precision and fineness of the movements produced, but generally show less force- from the muscles of mastication, the lateral pterygoid is an example.
    Muscles with a large number of fibers controlled by a single motor neuron show grosser, more powerful movements, but with less precision- like the masseter.
    Motor units function individually by contracting when stimulated by their motor neuron. When the neuron stops sending the message to contract, the muscle fibers relax.
  • When looking at a muscle as a whole, it can show 3 different types of actions:
    The muscle can contract isotonically- the overall length of the muscle shortens as it contracts, and the muscle acts as a mover of the body part in question, like the masseter when closing the mouth, or the biceps when curling the arm.
    Muscles can also contract isometrically- the overall length of the muscle stays the same as the muscle fibers contract against an opposing force or object, producing force of their own, but no movement. This occurs in the masseter when clenching the teeth together or biting on a hard object. Isometric contraction can act to hold or stabilize a part during function.
    The 3rd type of action is controlled relaxation. This is the slow, smooth, deliberate relaxation and lengthening of a previously contracted muscle. Controlled relaxation of certain muscles while other muscles contract allows for coordination of movements.
  • For the masticatory system to work properly, the actions of all of the different muscles must be coordinated, with each performing its specific task in order to work together with the other muscles to accomplish a given movement- the complex mandibular movements aren’t just a function of a single muscle contracting.
    For example, to perform a given movement, some muscles will contract isotonically to move the part, others will contract isometrically to stabilize other parts, and opposing muscles will undergo controlled relaxation to allow these muscles to perform their tasks. All of these complex contractions and relaxations are controlled and organized by the CNS.
  • The nervous system controls the function of the masticatory system.
    In general, nerve impulses travel through afferent, sensory neurons to the CNS after sensory receptors are activated by various stimuli. Return impulses travel back from the CNS through efferent, motor neurons to muscles to produce an action.
    For the masticatory system, most sensory and motor innervation is provided by the trigeminal nerve.
  • Many different areas and levels of the brain are involved in receiving and processing sensory input. Sensory impulses travel along the trigeminal nerve fibers and enter the brainstem to synapse with one or more of several different trigeminal nuclei. Some impulses, such as reflex actions, may be acted upon here at this level, while others may be sent further on to higher brain areas like the thalamus, which acts as a processing and control centre. Along the way, impulses may be modified by input from other areas of the brain, such as the reticular formation, which can enhance or inhibit impulses- making them stronger or weaker, or the hypothalamus, which controls internal bodily functions and may modify impulses based on this. After being directed by the thalamus, impulses may then pass higher up to the cerebral cortex, where they’re interpreted and acted upon consciously if necessary.
  • Proper function of the masticatory system is dependant upon the CNS receiving information from it’s various components, both about the parts themselves and about surrounding conditions. This job falls to the various types of sensory receptors, which detect and monitor specific kinds of stimuli and relay information to the CNS. Some of these receptors, located throughout the masticatory system, detect such things as pain, while others send information about position and movement.
    The 4 major types of receptors in the masticatory system, each with its own function, are muscle spindles, Golgi tendon organs, Pacinian corpuscles and nociceptors. Muscle spindles and Golgi tendon organs have proprioceptive functions, monitoring length in muscles and tension in tendons respectively. Pacinian corpuscles, found in various tissues, detect movement and firm pressure, while nociceptors detect stimuli and relay the information as sensations of pain
  • Mandibular movements, brought about by motor nerve impulses, can be of 3 different types, each initiated and controlled at a different level of the CNS.
    They can be voluntary- as a result of conscious thought, controlled by the cerebral cortex.
    They can be involuntary- a reflex action, without conscious effort, as a direct response to a stimulus
    They can be automatic- an acquired, repetitive pattern of movement (e.g. chewing), controlled at a subconscious level, but capable of being modified by, or brought under, conscious control.
  • A reflex is an involuntary movement, usually protective in nature, that takes place without conscious control in response to a stimulus. It takes place at the level of the spinal cord or cranial nerves, without involvement of the cortex or other higher brain centres. There are 2 important reflexes found in the masticatory system- the myotatic reflex and the nociceptive reflex.
  • The myotatic reflex (stretch reflex) happens when a muscle is quickly stretched. The muscle spindles send impulses to the trigeminal nuclei, from which motor impulses are sent back, resulting in the contraction of the stretched muscle. An example of this reflex is if a sudden downward blow is applied to the chin- this causes the elevator muscles to contract, snapping the jaw closed. A subtler form of this reflex is involved in determining the resting position of the jaw- receptors respond to the passive stretching of the muscles by gravity, and reflex action results in muscle tonus, keeping the jaw at its resting level. If it weren’t for this reflex, the jaw would fall so far due to gravity that it would dislocate itself.
    The nociceptive reflex (flexor reflex) is almost the reverse. It helps to protect the teeth and surrounding structures by causing the jaw to drop open when a hard object is unexpectedly encountered while chewing. The jaw elevating muscles are inhibited, while the jaw opening muscles are activated. An example of this reflex occurs when accidentally biting on a cherry or olive pit.
  • Automatic movements are controlled by an area of the brainstem called the central pattern generator. This group of neurons coordinates the timing of antagonistic muscle activity for rhythmic, subconscious functions such as chewing and swallowing. These activities are somewhere between voluntary and involuntary- they can be altered by cortical input, whether by conscious acts, or unconsciously influenced by stress or emotions.


  • 1. ANATOMY OF STOMATOGNATHIC SYSTEM INDIAN DENTAL ACADEMY Leader in continuing dental education
  • 2. Definition  According to Dorland’s medical dictionaryStomatognathic - stomato (mouth) + gnathic (jaws) which means mouth & the jaws collectively forms stomatognathic system.
  • 3. Components    Introduction Osseous anatomy Temporomandibular Joint.          Articular Disc. Condyle/Disc Assembly. T M Jt Ligaments. Muscles. Mastication. Muscles of mastication. Tongue Regulation of muscle activity. Reflexes.
  • 4. Introduction    Bones form the basic underlying structure of the stomatognathic system. Three main bones make up the skeletal portion of the stomatognathic system- the maxilla, the mandible, and a portion of the temporal bone of the skull. The maxilla and mandible are the bones that hold the teeth, while the temporal bone is the site of the mandible’s articulation with the skull.
  • 5.    Muscles move the mandible Contacting bony surfaces, upholstered with avascular, dense, fibrous connective tissue influence the direction of the mandible’s movements Ligaments limit the mandibles range of motion, acting as a leash to restrain it from travelling too far.
  • 6.
  • 7. •Maxilla & mandible are derived from 1st pharyngeal arch. Muscles of mastication are derived from mesoderm of 1st branchial arch
  • 8. The Mandible     The mandible forms the lower part of our face. It is suspended from the skull by muscles, ligaments and soft tissues, and doesn’t itself attach bone-to-bone to the maxilla, but hangs in space. U-shaped bone, contains mandibular teeth in alveolar process. Suspended from skull by muscles & ligaments. Major structural parts- condyle, coronoid process, ramus, angle, alveolar process, mental protuberance.
  • 9.
  • 10.
  • 11. The Condyle  Articular portion of the mandibleConsists of a neck- head & the articular surface  Head of the condyle  Oblong (football shaped), convex in all directions, but more curvature anteroposteriorly  15-20 mm wide medio-laterally, 8-10mm antero-posteriorly.  2 poles- medial & lateral- medial larger.  Posterior part of articular surface larger than anterior.
  • 12. Mandible- looking down from above.  The condyles are aligned at 90 degrees to the top of the ramus, but due to the flaring out of the mandible at the posterior,they are positioned such that the medial pole is more posterior than the lateral pole is- they make an angle to the horizontal that runs posteriorly at the medial aspect. Lines going through the poles of the condyles aim at the anterior edge of the foramen magnum of the skull.
  • 13. The Maxilla    Composes most of upper part of face & contains maxillary teeth. Fused to skull & hence non-mobile. Major intra-oral parts- alveolar process, palatal process, incisive foramen, mid-palatal suture, maxillary tuberosity.
  • 14.         The body of the maxilla has four surfaces: Anterior or facial surface Posterior or infratemporal surface Superior or orbital surface. Medial or nasal surface. It has four processes: Frontal. Zygomatic. Alveolar. Palatine.
  • 15. The Temporal Bone   Part of the skull with which the mandible articulates. Condyle articulates with concave mandibular fossa.
  • 16. The Temporomandibular Joint     Main functional parts are mandibular condyle, mandibular fossa & articular disc. Ginglymoarthrodial joint- allows hinging and gliding motions. Classified as compound joint- articular disc functions as a third, non-ossified bone. Articular surfaces covered with dense, fibrous connective tissue.
  • 17. Osseous Anatomy Of - T M Jt
  • 18. The Mandibular Fossa      Also called articular fossa & glenoid fossa. Posterior bordersquamotympanic fissure- thin bone. Medial wall -temporal bone- steep Anterior border - convex articular eminence-thick, dense bone. Slope of articular eminence & Squamotympanic medial wall are major fissure determinants of mandibular movement.
  • 19. The Articular Disc      Composed of dense, smooth, fibrous connective tissue. Mostly devoid of nerves & blood vessels Biconcave shape. Thickest at posterior border & medial border. Condyle articulates in thin intermediate zone.
  • 20. Saggital veiw
  • 21. Condyle/Disc Assembly    Condyle, articular disc & mandibular fossa surrounded by soft tissue attachments. Attachments aid in structure of joint, positioning and function of joint components. It consist of ligamentous attachments, elastic and collagenous connective tissue attachments and muscle attachment .
  • 22. LIGAMENTS  Bands of non-elastic collagenous tissue.  Function to passively limit range of movement & protect joint structures.
  • 23.  5 ligaments associated with TMJt. 3 functional, 2 accessory Functional:     Collateral (discal) ligaments Capsular ligament Temporomandibular ligament Accessory:   Sphenomandibular Stylomandibular
  • 24. Collateral (Discal) Ligaments     2 collateral ligaments- Medial & lateral. Stiff, collagenous connective tissue. Divide TMJ mediolaterally into superior & inferior joint cavities. Help keep disc positioned on condyle, allow anteriorposterior rotational movement.
  • 25. Capsular Ligament   Surrounds entire TMJ. Runs from neck of condyle to temporal bone & articular eminence, surrounds mandibular fossa, 360 degrees around.
  • 26. Capsular Ligament Functions: Prevent dislocation of articulating surfaces.  Proprioception.  Contains synovial lining – produces synovial fluid. 
  • 27. Temporomandibular Ligament  Outer Oblique Portion – articular eminence to neck of condyle – limits opening of mouth – influences nature of opening movement  Inner Horizontal Portion – articular eminence to head of condyle & disc – limits posterior movement  Both are closely related physically with capsular ligament
  • 28. Accessory Ligaments  Sphenomandibular Ligament • Medial view – sphenoid bone to lingula. – non-functional  Stylomandibular Ligament – styloid process to angle of mandible – limits protrusive movement
  • 29. Lateral Veiw
  • 30. Joint Cavities   TMJ is divided into 2 distinct joint cavities by articular disc and ligaments: Superior joint cavity – Between articular disc & mandibular fossa – Responsible for gliding movements  Inferior joint cavity – Space between articular disc & condyle – Responsible for hinging movements
  • 31. Movements Of Mandible
  • 32. Synovial Fluid    Joint capsule lined by specialized endothelial cells- synovial lining. Produces synovial fluid, fills both joint cavities. Function- lubrication & metabolism. 2 mechanisms- boundary lubrication & weeping lubrication.
  • 33.  Blood supplyBranches from superficial temporal and maxillary arteries. Veins follows arteries.  Nerve supplyAuriculotemporal nerve and massetric nerve.
  • 34. Muscles   Muscle fibers grouped into motor units. Motor unit consists of a group of muscle fibers all innervated by 1 motor neuron. Functional unit of muscles  Number of muscle fibers per neuron varies according to function of muscle   fewer fibers/neuron= less force, greater precision of movement- e.g. lateral pterygoid more fibers/neuron= greater force of movement, less precision- e.g. masseter
  • 35. Actions of Muscles    3 types of muscle action: Isotonic- overall muscle length shortens during contraction- primary movement. Isometric- overall muscle length does not shorten during contraction- develops force, but no movement- stabilization & fixation. Controlled relaxation- slow, smooth, relaxation and lengthening of previously contracted muscle- coordination of movements.
  • 36. The origin can be thought of as generally being the more stable, more “fixed” end of the muscle, and when the muscle contracts, it pulls the part at the insertion towards it.
  • 37. MASTICATION  Mastication (chewing) is the first movement of the digestive tract.  Importance of mastication. The coarse chunks of food are broken down to smaller particles. This breaking down has the following advantages (i) It increases the surface area . (ii) In case of some vegetable foods, where the surface coating of the food is made up of cellulose or hemicellulose, mastication causes exposure of the inner digestible material. The cellulose or hemicellulose is indigestible in human di-gestive system but the noncellulose inner material is digesti-ble. Thus digestion is facilitated (iii) It helps in the flow of saliva (iv) It helps in subsequent deglutition. 
  • 38.    The teeth are designed for chewing, the anterior teeth (incisors) providing a strong cutting action and the posterior teeth (molars), a grinding action. All the jaw muscles working together can close the teeth with a force as great as 55 pounds on the incisors and 200 pounds on the molars. Much of the chewing process is caused by a chewing reflexThe presence of a bolus of food in the mouth at first initiates reflex inhibition of the muscles of mastication, which allows the lower jaw to drop. The drop in turn initiates a stretch reflex of the jaw muscles that leads to rebound contraction. This automatically raises the jaw to cause closure of the teeeth, but it also compresses the bolus again against the linings of the mouth, which inhibits the jaw muscles once again, allowing the jaw to drop and rebound another time; this is repeated again and again.
  • 39. EQUILIBRIUM THEORY   States that an object subjected to unequal force will be accelerated and thereby will move to different position in space. It follows that if any object is subjected to a set of force but remains in the same position those forces must be in a balance or equilibrium . From this perspective the dentition is obviously in equilibrium since the teeth are subjected to variety of forces but don’t move to a new location under usual circumstances The duration of force is more important than its magnitude, due to its biological effect.
  • 40. MUSCULAR WEAKNESS SYNDROME • Causes mandible to drop down away from the facial skeleton • Distortion of facial proportions, increased facial height • Excessive eruption of posterior teeth, narrowing of maxillary arch and anterior open bite.
  • 41. Muscles producing Movements of mandible  Depression- Lateral pterygoid (mainly) Digastric, geniohyoid and mylohoid muscles help when the mouth is open wide or against resistance.  Elevation - Masseter - Temporalis - Medial pterygoid (both sides)
  • 42.  Protrusion – Lateral & medial pterygoids.  Retraction – Temporalis (post fibers).  Lateral or side to side movement - Medial & lateral pterygoids together.
  • 43. Muscles of mastication   There are several different groups of muscles associated with the masticatory system- some are directly involved with mandibular function, others are accessory in nature and just help out. The muscles of mastication are the primary functional muscles that perform the majority of mandibular movements. The suprahyoid group contains the muscles responsible for mouth opening, along with others , the infrahyoids, help to co-ordinate mandibular function. The posterior neck musculature is active in stabilizing and balancing the head, allowing the other to perform the many to work together complicated movements that are possible.
  • 44. Muscles of mastication       Masseter . Temporalis. Medial pterygoid. Lateral pterygoid. Hyoid muscles. Auxillary oral muscles.
  • 45. Masseter Superficial portion   Origin-anterior 2/3rd of zygomatic arch. Insertion-coronoid process,ramus and angle of mandible. Function-powerful elevator Deep portion   Origin-medial surface of zygomatic arch Insertion-coronoid process,ramus & angle of mandible. Function- elevation & retrusion.
  • 46.
  • 47.  A study was done by( Gedrange T etal J Appl Gnet 46 ,2005) to determine the myosine heavy chain proteins (MyHC) and MyHC mRNA in masseter muscles of patients with different mandibular positions. 10 patients were selected with distal and mesial malocclusion, and amount of MyHC and its different isoforms was determined by western blot essay and PCR. The anterior part of masseter muscle showed more type i and 2x myhc in distal occlusion than in the mesial occlusion.
  • 48. Medial pterygoid Origin :  Medial surface of lateral pterygoid plate. Insertion :  Medial surface of the angle of the mandible. Function :  Elevation & protrusion. Medial pterygoid
  • 49.
  • 50.
  • 51.
  • 52. Temporalis muscle Anterior portion   Origin : anterior temporal fossa Insertion : coronoid process Function : elevation Middle portion   Temporalis muscle Origin : Mid temporal fossa Insertion : coronoid process Function : elevation & retraction Posterior portion   Origin : posterior temporal fossa Insertion : coronoid process Function : retrusion
  • 53. Temporalis muscle function
  • 54. Lateral pterygoid Inferior head of lateral pterygoid  Origin:lateral surface of lateral pterygoid plate.  Insertion:neck of condyle.  Function : protrusion Superior head of lateral pterygoid  Origin : infratemporal surface of greater sphenoid wing.  Insertion : articular capsule,disc & neck of condyle.  Function : protractor of disc in conjuntion with elevator muscles
  • 55.
  • 56. Lateral pterygoid muscle function
  • 57. Nerve supply Motor nerve supply of masticatory muscles -Mandibular division of trigeminal nerve
  • 58. Blood supply to masticatory muscles Blood supply to muscles of masticationMaxillary Artery
  • 59. • A study [Gedrange T etal Rofo. 2005 Feb;177(2):204-9 ] was done to determine the relationship between the morphological parameters of the masticatory muscles and the jaw bone by computer tomography, lateral cephalogram and denture models. It showed higher densities of medial pterygoid, masseter and genioglossus in deep bite individuals than in the open bite cases. Significant difference in the muscle cross section of the masseter muscle was found in individuals with retroclined maxillary incisors and the individuals with open bite.
  • 60.
  • 61. Orbicularis oris & buccinator muscles Orbicularis oris Intrinsic part   Origin - superior incicivus from maxilla;inferior incicivus,from mandible Insertion – angle of mouth Buccinator Orbicularis oris Extrinsic part   Origin - thickest middle stratum,derived from buccinator & thick superficial stratum Insertion - lips & the angle of the mouth. Action  Closes & purses the mouth
  • 62. Buccinator muscleOrigin : Upper fibers from maxilla opposite Insertion : straight to the upper lip to molar teeth. Lower fibers from mandible opposite to molar teeth straight to the lower lip Middle fibers from ptergomandibular decussates before raphe passing to the lips Action – flattens cheek against gums & teeth. It is also called as whistling muscle.
  • 63. • A study done by Jung MH et al (Am J Orthod Dentofacial 2003 Jan) to evaluate the influence of force of orbicularis muscle on the incisor position and craniofacial morphology where average and maximum upper lip force was determined by a device ‘y’ meter. The skeletal structure and the incisal angulation were recorded by lateral cephalogram. The result showed that the upper incisor proclination was significantly related to the magnitude of the orbicularis oris force. So the disuse atrophy of orbicularis might be an significant factor in the development of malocclusion.
  • 64. BUCCINATOR MECHANISM It is a continuous muscle band that encircles the dentition and is anchored at the pharyngeal tubercle. Components  Orbicularis oris  Buccinator  Pterygomandibular raphae  Superior constrictor of pharynx  Opposing the buccinator mechanism there is a very powerful muscle – tongue; which begins it’s activity even before birth. 
  • 66. Suprahyoid muscles    Geniohyoid . Mylohoid . Digastric . Stylohyoid. Function :  Elevate hyoid bone & depress mandible when the mouth is wide open or against resistance ; it is secondary to lateral pterygoid .
  • 67.
  • 68.
  • 69. Suprahyoid muscle function
  • 70. Infrahyoid muscles    Thyrohyoid . Sternohyoid . Omohyoid . Function :  Lowers hyoid bone allowing suprahyoids to depress mandible.
  • 71. Tongue
  • 72. Development of tongue
  • 73. Papillae of the Tongue  These are projections of mucous membrane or corium which give the anterior two-thirds of the tongue its characteristic roughness. These are of the following three types.  Vallate or circumvallate papillae - They are large in size 1-2 mm in diameter and are 8-12 in number. They are situated immediately in front of the sulcus terminalis. Each papilla is a cylindrical surrounded by a circular sulcus. The walls of the papilla are raised above the surface.
  • 74.  Fungiform papillae are numerous near the tip and margins of the tongue but some of them are also scattered over the dorsum. These are smaller than the vallate papillae but larger than the filiform papilla consists of a narrow & a large rounded head.they are distinguished by their bright red colour.  Filiform papillae cover the presulcal area of the dorsumof the tongue & give it a characteristic velvety appearance, they are the smallest & most numerous of the lingual papilla.
  • 75. Muscles of tongue    Each half contains four intrinsic and four extrinsic muscles. Intrinsic muscles 1. Superior longitudinal 2. Inferior longitudinal 3. Transverse 4. Vertical Extrinsic muscles 1. Genioglossus 2. Hyoglossus 3. Styloglossus 4. Palatoglossus
  • 76. Nerve supply of tongue Sensory supply Root Ant 2/3-lingual Post 1/3 nerve for Vagus Both general and general nerve taste sensation are sensation. carried by Chorda glossopharyngeal tympani for nerve special taste sensation. Motor supply Hypoglossal nerve except palatoglossus which is supplied by cranial part of the accessory nerve.
  • 77.
  • 78. Blood supply of tongue   Arterial supplyLingual artery branch of ECA Root of tongue is supplied by tonsillar & ascending pharyngeal arteries. Venous drainage2 venae comitantes accompany lingual artery. Deep lingual vein is the principal vein of tongue.
  • 79. Lymphatic drainage of tongue    Tip of tongue bilaterally drains to submental nodes. Right & left ½ of the remaining part of the anterior 2/3rd of the tongue drain unilaterally to the submandibular nodes. Posterior 1/3rd drains to Jugulo-digastric nodes.
  • 81. TASTE      Different type of taste buds are perceived by different papillae which contain taste buds Circumvallate –bitter Foliate – sour Fungiform - at the tip of the tongue - sweet, and at periphery - salty Tastes are transmitted to the CNS by different nerve roots.
  • 82. Speech         Bi labialsounds -[m], [b] and [p] are bilabial stops (plosives) Labial-alveolar - [t], [d], or [n] sound. Labiodental – [f] &[v]. Dento alveolar – [t], [d]. Interdental consonants – [n],[l]. Coronal – [s],[z]. Velar – [g] ,[k] ,[q]. Uvular fricative - [χ].
  • 83. According to Proffit, the speech problems related to malocclusions are Speech sounds problem Related malocclusion S,Z (sibilants) lisp Anterior open bite T,D (linguoalveolar) Difficulty in production Lingual position of max. incisors F,V (labiodental) distortion Skeletal class III Th, sh, ch (linguo-dental) distortion Anterior open bite
  • 84. ANATOMY OF STOMATOGNATHIC SYSTEM …..continued part - 2 Presented by- Dr.Neelesh Shah Done Under The Guidance OfProfessor.Ashima.Valiathan B.D.S {Pb}, D.D.S, M.S{U.S.A} Director of P.G studies Department of Orthodontics, Manipal College Of Dental Sciences, Manipal.
  • 85.  Swallowing (Deglutition)  Swallowing is a complicated mechanism, principally because the pharynx subserves respiration as well as swallowing. The pharynx is converted for only a few seconds at a time into a tract for propulsion of food. It is especially important that respiration not be compromised because of swallowing. In general, swallowing can be divided into(1) Voluntary stage. (2) Pharyngeal stage. (3) Esophageal stage. 
  • 86.  Effect of the Pharyngeal Stage of Swallowing on RespirationThe entire pharyngeal stage of swallowing usually occurs in less than 6 seconds, thereby interrupting respiration for only a fraction of a usual respiratory cycle. The swallowing center specifically inhibits the respiratory center of the medulla during this time, halting respiration at any point in its cycle to allow swallowing to proceed. Yet even while a person is talking, swallowing interrupts respiration for such a short time that it is hardly noticeable.
  • 87. • Voluntary Stage of SwallowingWhen the food is ready for swallowing, it is "voluntarily" squeezed or rolled posteriorly into the pharynx by pressure of the tongue upward and backward against the palate. From here on swallowing becomes entirely or almost entirely automatic and cannot be stopped.
  • 88. • Pharyngeal Stage of SwallowingAs the bolus of food enters the posterior mouth and pharynx stimulates epithelial swallowing receptor areas all around the opening of the pharynx, especially on the tonsillar pillars, and sends impulses from the trigeminal and glossopharyngeal nerves into the medulla oblongata cither into or closely associated with the tractus solitarius which receives essentially all sensory impulses from the mouth which initiate a series of automatic pharyngeal muscle contractions. The trachea is closed, the esophagus is opened, and a fast peristaltic wave initiated by the nervous system of the pharynx forces the bolus to pass into the upper esophagus, the entire process occurring in less than 2 seconds.
  • 89. • Esophageal Stage of Swallowing The esophagus functions primarily to conduct food rapidly from the pharynx to the stomach, and its movements are organized specifically for this function. The esophagus normally exhibits two types of peristaltic movements: primary peristalsis and secondary peristalsis. Primary peristalsis is simply continuation of the peristaltic wave that begins in the pharynx and spreads into the esophagus during the pharyngeal stage of swallowing. This wave passes all the way from the pharynx to the stomach in about 5 to 10 seconds. Food swallowed by a person who is in the upright position is usually transmitted to the lower end of the esophagus even more rapidly than the peristaltic wave itself, in about 5 to 8 seconds, because of the additional effect of gravity pulling food downward.
  • 90. • If the primary peristaltic wave fails to move into the stomach all the food that has entered the esophagus secondary peristaltic waves result from distention of the esophagus itself by the retained food; these waves continue until all the food has emptied into the stomach. The secondary peristaltic waves are initiated partly by intrinsic neural circuits in the myenteric nervous system and partly by reflexes that begin in the pharynx and are then transmitted upward through vagal afferent fibers to the medulla and back again to the esophagus through glossopharvngeal and vaga! efferent nerve fibers.
  • 91. Deglutition
  • 92. Tongue thrust
  • 93.  A case report by Dr.Valiathan A. AND Sameer H Shaikh. (J Ind Ortho Soc 1998;31:53-57) showed the effect of an abnormally large tongue in producing the spaces similar in appearance to primate spaces. A 28 year male patient of south Indian origin was presented with a chief complain of proclination of upper anterior teeth along with spacing between the same. His face was fairly symmetrical with convex facial profile, prominent nose, acute nasolabial angle and incompetence of lip. An additional lateral ceph was taken following the administration of radio- opaque contrast medium to highlight the dorsum of tongue and related soft tissue. Based on detailed examination of the tongue dimension, tongue volume, electromyographic activity and force exerted by the tongue, it was concluded that excessively large volume tongue and dimension produce excessive force which possibly causes the malocclusion.
  • 94.  A study by Dr.Ashima Valiathan & Padmapriya C V was done on tongue volume & tongue force exerted during swallowing to evaluate their effect on the dentition. cephalometric findings of the study group were compared with normal cases as well as togue volume & pressure were measured. The results showed an increase in tongue pressure of 33 cN compared to 20.5 cN in control group & also an increase in the occurance of mouth breathing & tongue & lip habits in the study group.Thus in the complex etiology of bimaxillary protrusion,environmental factors in the form of various habits & excessive tongue force play an important role.
  • 95. • A study by Jeryl D.English and Kamrin D.G.Olfert (Semin Orthod 11:164-169 2005 ) The article distinguishes between dental open bite and skeletal open bite malocclusions and reviews the etiologic factor and possible treatment options. The addition of light masticatory muscle exercise on two mixed detention cases is illustrated. The patients were treated with a bonded rapid palatal expander followed by a transpalatal arch and a mandibular lingual arch, high-pull headgear therapy and light masticatory muscle exercises for 1 minute five times per day. A third case illustrates an increase in the clenching exercises of at least 5 minutes per hour for 6 hours. This patient had changed her mind on orthognathic surgical treatment plans. Treatment results suggest that clenching exercises helped to control the vertical dimension and assist in closure of open bite malocclusions.
  • 96. Tooth
  • 97. Actions of Muscles   Action of different muscles is coordinated, each performing a specific action to work together to accomplish a given movement eg. some contract isotonically to move a part, some isometrically to stabilize, while others undergo controlled relaxation. Movements controlled by CNS.
  • 98. Neurologic Control of the Masticatory System    Nerve impulses, picked up by sensory receptors, travel through afferent neurons to the CNS Return impulses travel back from the CNS through efferent neurons to muscle to produce an action Most sensory + motor innervation for masticatory system provided by trigeminal nerve
  • 99. Neurologic Control of the Masticatory System  Areas of the brain involved are: – Brain stem (trigeminal nuclei). – Regulatory and modifying areas (e.g thalamus, reticular formation). – Cortex.
  • 100. Sensory Receptors   Detect stimuli and provide information to CNS Types: – Muscle spindles- proprioception – Golgi tendon organs- proprioception – Pacinian corpuscles- movement & firm pressure – Nociceptors- pain
  • 101. Neural Control of Mandibular Function  Movements can be: – Voluntary- conscious act – Involuntary- reflex – Automatic- acquired patterns of movement - e.g. chewing
  • 102. Reflexes      Movement takes place without conscious control Occurs without cortex involvement Protective in nature Results from stimulation of a receptor Masticatory reflexes – Myotatic reflex – Nociceptive reflex
  • 103. Reflexes  Myotatic reflex (stretch reflex)     occurs when a muscle is quickly stretched results in contraction of stretched muscle involved in determining rest position of jaw Nociceptive reflex (flexor reflex)   occurs when a hard object is encountered when chewing results in jaw dropping open
  • 104. Regulation of Muscle Activity     Automatic movements are controlled by the brainstem- central pattern generator. Coordinates timing of antagonistic muscle function. Somewhere between voluntary & involuntary lies rhythmic, subconscious functions- e.g. chewing, swallowing, etc. Can be altered by cortical input- conscious act or influenced by stress, emotion, etc.
  • 105. Temporo Mandibular disorder • Temporomandibular joint disorder (TMJD or TMD), or TMJ syndrome, is an acute or chronic inflammation of the temporomandibular joint, which connects the lower jaw to the skull. The disorder and resultant dysfunction can result in significant pain and impairment.
  • 106. Concepts of orthopedic stability   Musculoskeletal stable position – It is that position when the condyles are in their most superoanterior position in the articular fossae, resting against the poosterior slopes of articular eminences, with the articular disc properly interposed. The most stable occlusal position – It is the maximal intercuspation of teeth. This type of occlusal relationship furnishes maximum stability for the mandible while minimizing the amount of force placed on each tooth during function.
  • 107. • Optimal orthopedic stability in the masticatory system is to have even & simultaneous contact of all possible teeth when the mandibular condyles are in their most superoanterior position, resting against the posterior slopes of the articular eminences, with the disc properly interposed. ie- the musculoskeletal stable position of the condyles coincides with the maximal intercuspation position.
  • 108. Determinants of orthopedic stable position
  • 109. Closed and opened positions jaw closed jaw opened
  • 110. Types of TMD  • • •  Three most common temporomandibular disorders areMyofascial pain and dysfunction, Internal derangement, and Osteoarthrosis. Myofascial pain and dysfunction is by far the most prevalent. It is primarily a muscle disorder resulting from oral parafunctional habits such as clenching or bruxism. These habits are sometimes related to psychogenic disorders such as headache, chronic back pain, and irritable bowel syndrome. Stress, anxiety, and depression are key features of myofascial pain and dysfunction.
  • 111.   The term internal derangement describes a temporomandibular disorder in which the articular disc is in an abnormal position, resulting in mechanical interference and restriction of the normal range of mandibular activity. Osteoarthrosis is a localised degenerative disorder that affects mainly the articular cartilage of the temporomandibular joint and is often seen in older people.
  • 112. Precipitating factors  Over-opening the jaw beyond its range or unusually aggressive or repetitive sliding of the jaw sideways or forward (protrusive). These movements may also be due to abnormal habits or a malalignment of the jaw or dentition. This may be due to:
  • 113.       Modification of the occlusal surfaces of the teeth thorugh dentistry or accidental trauma. Speech habits resulting in jaw thrusting. Excessive gum chewing or nail biting. Excessive jaw movements associated with exercise. Repetitive unconscious jaw movements associated with bruxing. Size of foods eaten.
  • 114. Clinical features There are three cardinal features of temporomandibular disorders • Orofacial pain, • Joint noise, and • Restricted jaw function.
  • 115. • Patients describe either a generalised tight feeling, which is probably a muscular disorder, or the sensation that the jaw suddenly "catches" or "gets stuck," which is usually related to internal derangement. • Headaches, ear aches, tinnitus, and neck and shoulder pains are just a few of a number of non-specific symptoms that are often reported by patients with temporomandibular disorders.
  • 116. Differential diagnosis      Dental pain. Disorders of the ears, nose, and sinuses. Diseases of the major salivary glands. Neuralgias. Headaches.
  • 117. Myofascial pain dysfunction syndrome  There are four cardinal signs and symp-toms of the syndrome: (1) Pain, (2) Muscle tenderness; (3) A clicking or popping noise in the temporomandibular joint, (4) Limitation of jaw motion, unilaterally or bilat-erally in approximately an equal ratio, sometimes with deviation on opening.  Two typical negative disease characteristics: (1) An absence of clinical, radiographic or biochemical evidence of organic changes in the joint itself, (2) Lack of tenderness in the joint when it is palpated through the external auditory meatus.
  • 118. Functionally dislocated discs
  • 119. Types of disc displacements
  • 120. Reciprocal clicking and disc displacement with reduction (DDR)
  • 121. The “Road to Perdition”
  • 122. Adhesions
  • 123.
  • 124.
  • 125. Temporomandibular disorder screen examination.   Muscle palpation. TMJt palpation. Click Crepitus.   Range of mandibular motion. Occlusal evaluation
  • 126. Muscle palpation.
  • 127. TMJt palpation
  • 128. . Range of mandibular motion Occlusal evaluation
  • 129. How can i locate the musculoskeletally stable position of the condyles in fossa ??
  • 130. Manual method to achieve MSSP
  • 131. Use of leaf gauge to achieve MSSP
  • 132. Treatment Non-surgical treatment of temporomandibular disorders continues to be the most effective way of managing over 80% of patients. • Explanation and reassurance • Patient education and self care • Drug treatment (non-steroidal anti-inflammatorydrugs,opiates,tranquillisers, tricyclic antidepressants) • • • • Occlusal therapy – (70% of patients) Physiotherapy Behavioural therapy Surgical treatment – (5% of patients)
  • 133. Factors that reduce symptoms with occlusal appliance        Alteration in occlusal condition Alteration in condylar position Increase in vertical dimension Cognitive awareness Placebo effect Increase in peripheral input to the CNS. Regression to mean.
  • 134. • Study-by Magnusson T (Cranio 4(4):338-344 1986) A 5years longitudinal study - observed untreated subjects at age 15 years, & then again 20 years found that clicking is common in this age group & that clicking can come & go, unrelated to any major clinical symptoms. Therefore if patient reports the onset of a joint sound unrelated to pain and occlusal condition is being developed in harmony with the stable joint position, patient education regarding the problem may be all that is needed.
  • 135. Conclusion    Anatomy of stomatognathic system is the basic pillar for any dental clinician whose sound knowledge is very important; it helps us in diagnosis & treatment of many oral disorders. It also helps us in various treatment modalities like implant placement, diagnosing TMJt disorders, myofunctional pain dysfunction syndrome,etc. It’s knowedge helps an orthodontic treatment in such a manner that the finished result reflects a balance between the structural changes obtained and functional forces acting on the teeth and investing tissue at that time.
  • 136.  The orthodontist is challenged constantly with the task of providing each patient with acceptable esthetics and masticatory function. Although esthetics is often the patient’s immediate and primary goal, functional outcomes are far more important over the lifetime of the patient. Developing a sound functional masticatory system needs to be the primary goal of all orthodontic therapy. No other dental specialist routinely alters the patient's occlusal condition as a part of the therapy.
  • 137.  The orthodontist is in a unique position to improve or worsen the occlusal condition while carrying out the esthetic goals of the therapy. It therefore behooves the orthodontists to be knowledgeable of normal masticatory function and the goals that need to be achieved to maintain normal function. These goals should be met in all patients, those with and without masticatory dysfunction.
  • 138. References 1. 2. 3. 4. 5. 6. Atlas of anatomy- Grant`s 11th edition Lippincot Williams & Wilkins - 2005. Atlas of human anatomy- Neter`s 3rd edition Elsevier - 2006. Gray’s anatomy- 36th edition Elsevier - 2005. Human anatomy volume -3 B.D.Chaurasia 4th edition C B S Publication-2005. Human embryology – Inderbersingh 5th editionMac Millan India -1993. William f Ganong- Medical physiology 19th editionLange medical publication 2005.
  • 139. 8. Sujit Chaudhari- Concise medical physiology. 5th edition New central book agency - 2004 . 9. Guyton- Human physiology & mechanism of disease 11th edition W.B.Saunders 2006. 10. Langman`s Medical embryology 10th edition Lippincot Williams & Wilkins - 2006. 11. Jung MH,Yang WS etal- Effect of upper lip closing force on craniofacial structures.Am.J. Orthod .Dentofacial.Orthop Jan 2003 123,58-63,
  • 140. 12. Ashima Valiathan,Sameer H Shaikh-Malocclusion and the tongue :J Ind Orthod Soc,1988,31:53-57 13. T.M.Graber - The “three Ms”: Muscles, malformation, and malocclusion .Am. J. Orthodontics vol-49 number- 6 June 1963 14.Thomas P George, Valiathan Ashima, Arji I George & Denny J Payyappilly: Oral habits (Part II) Tongue thrusting. Kerala Dental Association. 1992; 15(3 & 4): 721-724
  • 141. 15. Ashima Valiathan ,Padmapriya C V- Comparison of tongue pressure, tongue volume and cephalometric values in kerela population with and without bimaxillary protrusion-a clinical study- J Ind Orthod Soc ,2003, 36;Page-158-163 16. Gedrange T ,Buttner- Myosine heavy chain protein and gene expression in the masseter muscle of adult patients with distal or mesial malocclusion. C,J.Apply.Genet,46,227-36.2005 17. Gedrange T etal- Computed tomographic examination of muscle volume ,cross section and density in patients with dysgnathia. [, 177(2),204-9,Rofo Feb 2005
  • 142. 18. Robert.E.Moyers-Handbook Of Orthodontics 4th Edition Year book medical publisher – 1998. 19. William.R. Proffit- Contemporary Orthodontics,3rd Edition.—Henry W.Fields.JR 3rd Edition Mosby - 2000. 20. T.M.Graber - Orthodontics Principles and Practice 4th Edition Elsevier - 2005. 21. Thomas M.Graber, Thomas Rakosi, Alexandre G.Petrovic-Dentofacial Orthopedics with Functional Appliance 2nd Edition Mosby year book - 1997.
  • 143. 22. Jeryl D.English and Kamrin D.G.OlfertMasticatory muscle exercise as an Adjunctive treatment for open bite malocclusions .Semin Orthod 11:164-169 © 2005. 23. Okeson, Jeffrey P. "Management of Temporomandibular Disorders and Occlusion"4th edition. Mosby, Inc. 2003 24. D. M. Laskin, C. S. Greene, W. L. Hylander.-TMDs: An Evidence Based-Approach to Diagnosis and Treatment. (2006) Eds: Quintessence Books, Chicago.
  • 144. 25. Clark GT.-A critical evaluation of orthopedic interocclusal appliance therapy. Design theory and overall effectiveness. J Am Dent Assoc 1984; 108: 359-364. 26. Clark GT, Adler RC- A critical evaluation of occlusal therapy. Occlusal adjustment procedures. J Am Dent Assoc 1885; 110: 743-750. 27. Stuart.C.White & Micheal.J.Paroah - Oral Radiology Principles & Interpretation –4th Edition Mosby - 2000. 28. Shafer William.G- A Text Book Of Oral Pathology 4th Edition W.B.Saunders ompany 1983.
  • 145. Thank you Leader in continuing dental education