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Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.

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  • 1. Contents  Introduction  History  Definitions  Classification  Epidemiology  Etiology  Development of functional disturbances in masticatory system  Predisposing factors  Initiating factors  Perpetuating factors.  Occlusal conditions  Parafunctional habits  Trauma  Emotional stress  Deep pain output  Signs and symptoms of TMDS  Functional disorders of muscles  Functional disorders of TMJ  Functional disorders of teeth  Other signs and symptoms  Summary  Conclusion  References  Introduction:  The masticatory apparatus is specialized unit that performs multiple functions including those of speaking, cutting & grinding food & swallowing.  TMJ disorder (TMD) are among the most misdiagnosed & mistreated maladies in medicine.  Multifactorial origin
  • 2.  The term TMD are collective term embracing a member of clinical problems that involve the masticatory musculatures, the TMJ & associated structure or both This disorders are characterized by  Facial pain in the region of the TMJ & for the muscle of mastication.  Limitation or deviation in the mandibular range of motion.  TMJ sounds during jaw movements & function.  History:  348 BC: Hippocrates described a condition of TMJ dislocation.  1814: Hey had described internal derangement for a localized mechanical fault interfering with smooth articular function.  1842: Cooper reported on subluxation of the TMJ as a distinct entity. He observed patients with snapping jaw & registered this symptom as an “ internal derangement of the jaws”  1887: Surgical correction was described by Annandale.  1918: Pringle explained clicking & popping of the TMJ as a sign of anterior displacement of the meniscus.  1934: Costen was first to indicate an occlusal etiology in TMJ pain. He reported association of the bite over closure with symptoms like ear pain, sinus pain, decreased hearing, tinnitus, dizziness, burning & vertigo & occipital headache.  1947: Norgaard used orthographic techniques to radiographically demonstrate anterior disc displacement in clicking or popping TMJ.  1950-60: muscular cause not directly related to occlusion was proposed Schwartz coined the term Temporomandibular pain syndrome.  1970: advances in diagnostic imaging have resulted a better understanding of the intracapsular problem associated with TMD. Farrar & McCarthy rejuvenated the concept of internal derangement with meniscus displacement. Definition of TMD  Acc to Schiffman, Haley, Shapiro (1990)
  • 3. the TMD encompasses many disorders of the masticatory musculature (i.e. myositis, muscle spasm, muscle contracture, & myofascial pain syndrome) and TMJ ( internal derangements with or without reduction and degenerative joint disease)  The AAOP ( in 1993 & 1996) refined TMD as a collective term embracing a number of clinical problems that involve the masticatory musculature, the temporomandibular joint and associated structures or both. GPT - 8  Conditions producing abnormal , incomplete or impaired function of the temporomandibular joint.  A collection of symptoms frequently observed in various combinations first described by Costen (1934) which he claimed to be reflexes due to irritation of the auriculotemporal nerve and / or corda tympanic nerve as they emerged from tympanic plate.  It is caused by altered anatomic relations and derangements of the TMJ associated with loss of occlusal vertical dimension, loss of posterior tooth support, and / or other malocclusions. The symptoms can include headache about the vertex and occiput, tannitus, pain about the ear, impaired hearing and pain about the tongue. Classification of diseases of Temporomandibular joint  Bell in 1960  3 subgroups:  Intracapsular conditions  Capsular conditions  Extracapsular conditions  In 1982, 5 subcategories  Masticatory muscle disorder  Disk interference disorder  Inflammatory disorder  Chronic hypomobilities  Growth disorders
  • 4. Acc. to American Academy of Orofacial Pain Diagnostic category Diagnosis Cranial bones Congenital & developmental disorders Aplasia Hypoplasia Dysplasia(1st & 2nd brachial arch anomalies, hemifacial microsomia, Pierre syndrome, Treacher Collin syndrome) Condylar hyperplasia Prognathism, fibrous dysplasia. Acquired disorders Neoplasia Fracture Temporomandibular joint Disorders Deviation in form Disk displacement (with reduction; without reduction) Dislocation Inflammatory conditions (synovitis, capsulitis) Arthritides (osteoarthritis, osteoarthrosis polyarthritides) Ankylosis (fibrous, bony) Neoplasia Masticatory muscle Disorders Myofascial pain Myositis Spasm Protective splinting Contracture
  • 5.  Between 65 and 85% of people experience some symptoms of TMD during their lives, and approximately 12% experience prolonged pain or disability that results in chronic symptoms.  Only about 5 to 7% have symptoms severe enough to need treatment.  TMD patients are similar to headache and back pain patients with respect to disability, psychosocial profile, and pain intensity, chronicity, and frequency.  The lower prevalence of TMD signs and symptoms in older age groups supports the probability that most TMD are self-limiting.  TMD are most prevalent between the ages of 20 and 40 years and predominantly affect women.  The reason why women make up the majority of patients presenting for treatment is still unclear.  In a community-based study, a greater likelihood of developing TMD was found if oral contraceptives were used and, in women over 40 years of age, if estrogen replacement was used.  While the prevalence of TMD is highest in the 20- to 40-year age range, signs and symptoms of masticatory-muscle and joint dysfunction are commonly observed in children.  The cause may be acute reactive depression, disk displacement, with or without reduction, internal derangement due to previous injury. 1
  • 6.  Development of functional disturbances in the masticatory system Normal fuction  Chewing  swallowing  speaking  carried out by the complex neuro muscular control system. Events  During normal function of the masticatory system, events can occure that may influence function.  Local events  systemic events. 1 TMD symptoms =physiologic tolerance Normal function + event >
  • 7. Local events  Any change in sensory or proprioceptive input.  Placement of improperly occluding crown  or it may be secondary to trauma involving local tissues e.g. post injection response of L.A.  trauma due to wide opening (i.e. strain) or unaccustomed use (i.e. bruxisum). systemic events  The entire body and CNS are involved.  E.g. emotional stress. Physiologic tolerence  All individuals do not respond in the same manner to the same event.  Each patient has the ability to tolerate certain events without any adverse effect this is called physiologic tolerance which can be influenced by both local and systemic factors. Local factors  Lack of occlusal stability- genetic, developmental, or iatrogenic causes.  TMJ instability- alteration in normal anatomic form e.g.- disc displacement, arthritic conditions, lack of harmony between stable intercuspal position (ICP) and musculoskeletally stable (MS) position of the joint. Systemic factors  Systemic factors which influence the patient’s physiologic tolerance are, genetic, gender, diet, acute and chronic diseases, overall physical condition of the patient. Structural tolerance and development of symptoms.  When functional change exceeds a critical level, alteration of tissues begins this level is called structural tolerance level.  The initial breakdown is seen in the structures with the lowest structural tolerance.  Therefore the breakdown sites varies from individual to individual.
  • 8.  The etiology of TMD remains mired in controversy. It is generally agreed that the etiology of symptoms of TMD is multifactorial. That is several different factors acting alone, or in varying combinations may be responsible.  Predisposing factor – factors that increase the risk of TMD or orofacial pain developing.  Initiating factors – factors that cause the onset of disorder.  Perpetuating factors – factors that interfere with healing and complicate management .  Predisposing factors can be subdivided into : Systematic factors – medical conditions such as rheumatic infections, nutritional and metabolic disorders can influence masticatory system to an extent that TMD may emerge. Psychologic factors - Personality, behaviour can affect masticatory system. Structural factors – All types of occlusal discrepancies, improper dental treatment, postural abnormalities ,skeletal deformation, past injuries etc. Genetic factors.  Direct precipitating or initiating component:
  • 9.  Trauma from hyperextension (e.g. dental procedure, oral intubation for G. A., yawning, hyperextension associated with cervical trauma)  Micro & macro trauma  Adverse or overloading of joint structures  Parafunctional habits (nocturnal bruxing, tooth clenching, lip or cheek biting)  Perpetuating factors or sustaining factors:  Mechanical & muscular stress  Metabolic problems  Mainly behavioral, social & emotional difficulties  Five major factors associated with TMD  1) Occlusal condition  2) Trauma  3) Emotional stress  4) Deep pain input  5) Parafunctional activities. occlusal condition.  Pullinger et al. (j prosthet dent 2000,83:66-75),  studied 11 possible occlusal factors.  Concluded that,  No single occlusal factor was able to differentiate patient from healthy subjects.  Four factors, however occurred mainly in TMD patients and were rare in normal subjects  1) The presence of a skeletal anterior open bite.  2) Retruded contact position (RCP) and ICP slides of greater than 2mm.  3) Overjets of greater than 4mm.  4) Five or more missing and unreplaced posterior teeth. Dynamic relationship between occlusion and TMD  Occlusal conditions affects TMD by one of the two ways  1) Occlusal conditions affects the orthopedic stability of the mandible.  2) Acute changes in occlusion . 
  • 10. Occlusion and orthopedic stability Occlusion and orthopedic stability
  • 11.  Degree of orthopedic instability- discrepancy more than 1-2 mm  Amount of loading- bruxers are affected more than non- bruxers Acute changes in occlusion and TMD  Mainly affects the activities of masticatory muscles.  Muscle activities are basically divided in to  1) Functional (chewing, speaking, swallowing)  2) Parafunctional (clinching and bruxism)
  • 12. Occlusal contacts and muscle hyperactivity  Precise effect of the occlusal condition on muscle hyperactivity has not been clearly established.  Williamson and Landquist demonstrated that certain posterior contacts can increase activity of the elevator muscles.  But Rugh et al. Shown that premature occlusal contacts do not increase bruxing activity (no correlation between occlusal contacts and muscle activities).  The difference between first and second study:- first study assesed the effects of occlusal contacts on conscious and controlled, voluntary mandibular movements (controlled by peripheral nervous system) while the second study assessed subconscious and uncontrolled, involuntary muscle activity (bruxisum) (controlled by CNS).  Thus sudden changes that disrupts the ICP can lead to a protective response of the elevator muscles (i.e. protective co-contraction) in conscious state which may lead to pain.  But this increased tonus or change in ICP do not cause any increase in bruxing activity which is controlled by CNS. Chronic occlusal interferences  1) Most common way is to alter muscle engrams so as to avoid the potentially damaging contacts and get on with the task of function.  2) Tooth movement to accommodate heavy loading.  Bruxism never occurs or accentuates because of occlusal problems.
  • 13.  Problems with bringing the teeth into occlusion are answered by muscles. However, once the teeth are in occlusion, problem with loading the masticatory structures are answered in the joints.  Therefore if one of these conditions exists, dental therapy is likely indicated. Trauma  Trauma seems to have greater influence on intracapsular disorders than muscular disorders.  Two types  1) Macrotrauma- any sudden force that can result in structural alteration e.g. blow on the face.  2) Microtrauma:- any small force that is repeatedly applied to the structures over a long period of time e.g. bruxism, clinching. Macro trauma  Sudden force on the condyle.  It can be direct or indirect.  The direct macro trauma can be open mouth trauma or closed mouth trauma. Open mouth direct macro trauma  Blow to the chin, when the teeth are separated (i.e., open-mouth trauma)- the condyle can be suddenly displaced from the fossa - ligaments resist this sudden displacement.  If the force is great, the ligaments can become elongated - resulting increased looseness can lead to discal displacement and to the symptoms of clicking and catching.
  • 14.  Unexpected macrotrauma to the jaw (as might be sustained during a fall or in a motor vehicle accident) may lead to discal displacement, dislocation, or both. Closed mouth direct macro trauma  Macrotrauma can also occur when the teeth are together (i.e., closed- mouth trauma) - the intercuspation of the teeth maintains the jaw position, resisting joint displacement.  Closed-mouth trauma is therefore less injurious to the condyle-disc complex.  Athletes who wear soft, protective mouth appliances have significantly fewer jaw-related injuries than those who do not.  Although ligaments may not be elongated, articular surfaces can certainly receive sudden traumatic loading. This type of impact loading may disrupt the articular surface of the condyle, fossa or disc, which may lead to alterations in the smooth sliding surfaces of the joint, causing roughness and even sticking during movement. Therefore this type of trauma may result in adhesions. Indirect macro trauma  Indirect trauma refers to injury that may occur to the TMJ secondary to a sudden force, but not one that occurs directly to the mandible. The most common type of indirect trauma reported is associated with a cervical flexion-extension injury (i.e., whiplash injury).
  • 15. Microtrauma  Microtrauma refers to any small force that is repeatedly applied to the joint structures over a long period of time loading exceeds the functional limit of the tissue, irreversible changes or damage can result. When the functional limitation has been exceeded, the collagen fibrils fragmented, resulting in a decrease i ness of the collagen network. This allows proteoglycan-water gel to swell and flow out the joint space, leading to a softening of articular surface. This softening is called chondromalacia.  Regions of fibrillation can begin to develop, resulting in focal roughening of the articular surfaces. This alters the frictional characteristics of the surface and may lead to sticking of the articular surfaces, causing changes in the mechanics of condyle-disc movement.  Continued sticking, roughening, or both leads to strains on the discal ligaments during movements and eventually to disc displacements.  Another way in which micro trauma affects is the hypoxia-reperfusion theory.
  • 16.  Another type of microtrauma results from mandibular orthopedic instability. As previously described, orthopedic stability exists when the stable ICP of the teeth is in harmony with the musculoskeletally stable (MS) position of the condyles  Bruxing patients with orthopedic instability are more likely to create problems than nonbruxers with the same occlusion. Emotional stress  The emotional centers of the brain have an influence on muscle function  Stress - activates hypothalamus - increase the activity of the gamma efferents - the intrafusal fibers of the muscle spindles contract.  Stress releasing mechanisms:- external and internal Deep pain input  Deep pain input- centrally excites the brain stem- produces muscle response (protective co-contraction)  It is normal body response to pain.  Intraoral pains like tooth pain, sinus pain, ear pain or even remote facial pains like cervical pain input may restrict the mouth opening. Parafunctional activities  Two types  1) Diurnal- occurs during day.
  • 17.  2) Nocturnal - occures during night.  DIURNAL ACTIVITIES - clinching and grinding, cheek and tongue biting, finger and thumb sucking, unusual postural habits, occupation related habits e.g. holding nails, pen in mouth, holding objects like telephone, violin under the chin. Nocturnal activities  Clinching (single episode of muscular contraction)  Bruxing (rhythmic contractions)  causes of bruxing activities emotional stress, certain medications, genetic predisposition, CNS disturbances, occlusal interferences ??? Etiological concepts :  Mechanical displacement theory:  Neuromuscular theory:  Muscle theory:  Psycophysiological theory:  Psychological theory:  A sign is an objective clinical finding that the clinician uncovers during a clinical examination.  A symptom is a description or complaint reported by the patient  patients are acutely aware of their symptoms yet may not be aware of their clinical signs.  Clinical signs and symptoms of TMDs can be grouped according to the structures affected  1) the Muscles.  2) the TMJs  3) the Dentition
  • 18. Functional disorders of the muscles  Two major symptoms  1) Pain  2) Dysfunction. Pain  Pain felt in musculature is called myalgia.  Often associated with fatigue and tightness.  It is related to vasoconstriction of the relevant nutrient arteries and accumulation of metabolic waste products. Within the ischemic area of the muscle, certain algogenic substances (e.g. bradykinin, prostaglandins) are released, causing muscle pain  The severity of muscle pain is directly related to the functional activity of the muscle involved. Therefore patients often report that the pain affects their functional activity.  When a patient reports pain during chewing or speaking, these functional activities are not usually the cause of the disorder.  Myogenous pain is a type of deep pain and, if it becomes constant, can produce central excitatory effects. These effects may present as sensory effects (i.e. referred pain or secondary hyperalgesia) or efferent effects (i.e. muscle effects), or they may even present as autonomic effects.  Muscle pain can reinitiate more muscle pain (i.e., the cyclic effect).  Another very common symptom associated with masticatory muscle pain is headache. Dysfunction  A decrease in the range of mandibular movement. When muscle tissues have been compromised by overuse, any contraction or stretching increases the pain. Therefore to maintain comfort, the patient restricts movement within a range that does not increase pain levels. Clinically this is seen as an inability to open widely.  An acute malocclusion may result from a sudden change in the resting length of a muscle that controls jaw position. When this occurs the patient describes a change in the occlusal contact of the teeth.  The mandibular position and resultant alteration in occlusal relationships depend on the muscles involved. For example, slight functional shortening of the inferior lateral pterygoid will cause disocclusion of the posterior teeth on
  • 19. the ipsilateral side and premature contact of the anterior teeth (especially the canines) on the contralateral side.  With functional shortening of the elevator muscles (clinically a less detectable acute malocclusion), the patient will generally complain of an inability to occlude normally. It is important to remember that an acute malocclusion is the result of the muscle disorder and not the cause Events  Various types of events can interrupt normal muscle function. These events can arise from either local or systemic factors  Local events that acutely alter sensory or pro-prioceptive input in the masticatory structures .  Systemic factors may also represent events that can interrupt normal muscle function.  Local events  1) Fracture of tooth  2) Restoration in supraocclusion  3) Trauma to local tissues e.g. L.A. inj  4) Chewing hard food  5) Chewing for long period  6) Opening mouth too widely e.g. yawning, dental treatments  Systemic events
  • 20. 1) Emotional stress 2) Acute illness. 3) Viral infections 4) Age 5) Gender 6) Diet 7) Genetic predisposition Protective co-contraction  Protective co-contraction is a CNS response to injury or threat of injury. This response has also been called protective muscle splinting.  In the presence of an injury or threat of injury, normal sequencing of muscle activity seems to be altered to protect the threatened part from further injury.  This coactivation of antagonistic muscles is thought to be a normal protective or guarding mechanism . If protective co-contraction continues for several hours or days, the muscle tissue can become compromised and a local muscle problem may develop. Local muscle soreness  Local muscle soreness is a primary, noninflammatory, myogenous pain disorder (i.e., noninflammatory myalgia). It is often the first response of the muscle tissue to prolonged co-contraction.  Although co-contraction represents a CNS-induced muscle response, local muscle soreness represents a condition characterized by changes in the local environment of the muscle tissues.  These changes are characterized by the release of certain algogenic sub- stances (i.e., bradykinin, substance P, and even histamine) that produce pain.  Along with protracted co-contraction, other causes of local muscle soreness are local trauma or excessive use of the muscle.  When excessive use is the cause, a delay in the onset of muscle soreness can occur  Local muscle soreness presents clinically with muscles that are tender to palpation and reveal increased pain with function. Structural dysfunction is common, and limited mouth opening results when the elevator muscles are involved. CNS EFFECTS ON MUSCLE PAIN  Activities within CNS either influence or originates muscle pains  The CNS responds in this manner secondary to one of three factors: (1) the presence of ongoing deep pain input,
  • 21. (2) increased levels of emotional stress (i.e., up-regulation of the autonomic nervous system), or (3) changes in the descending inhibitory system that lead to a decrease in the ability to counter the afferent input.  CNS induced muscle pain disorders are 1) Myospasm 2) Myofacial pain (trigger point myalgia) 3) Centrally mediated myaligia (chronic myocitis) 4) Chronic systemic myalgic disorders (fibromyalgia) Perpetuating factors in myalgia  Local perpetuating factors 1) Protracted cause 2) Recurrent cause 3) Therapeutic mismanagement.  Systemic perpetuating factors 1) Continued emotional stress 2) Sleep disturbances 3) Learned behavior 4) Secondary gain 5) Depression  They generally fall into three broad categories: (1) derangements of the condyle-disc complex, (2) structural incompatibility of the articular surfaces, and (3) inflammatory joint disorders  They generally fall into three broad categories: (1) derangements of the condyle-disc complex, (2) structural incompatibility of the articular surfaces, and (3) inflammatory joint disorders
  • 22.  Stimulation of the nociceptors creates inhibitory action in the muscles that move the mandible.  Therefore when pain is suddenly and unexpectedly felt mandibular movement immediately ceases (i.e., nociceptive reflex).  When chronic pain is felt, movement becomes limited and very deliberate (i.e., protective co-contraction).  Arthralgia from normal healthy structures of the joint is a sharp, sudden, and intense pain that is closely associated with joint movement. When the joint is rested, the pain resolves quickly. DYSFUNCTION  It presents as a disruption of the normal condyle-disc movement, with the production of joint sounds .  The joint sounds may be a single event of short duration, known as a click.  If this is loud it may be referred to as a pop.  Crepitation is a multiple, rough, gravel-like sound described as grating and complicated.  Dysfunction of the TMJ may also present as catching sensations when the patient opens the mouth. Sometimes the jaw can actually lock. CONTINUUM OF FUNCTIONAL DISORDERS OF THE TMJ
  • 23.  Disorders of the TMJs may follow a path of progressive events, a continuum, from the initial signs of dysfunction to osteoarthritis 1. Normal healthy joint 2. Loss of normal condyle-disc function the result of either: a. Macrotrauma that resulted in elongation of the discal ligaments b. Microtrauma that created changes in the articular surface, reducing the frictionless movement between the articular surfaces 3. Significant translatory movement begins between disc and condyle (resulting in displacement of disc) 4. Posterior border of disc becomes thinned 5. Further elongation of discal and inferior retrodiscal ligaments 6. Disc becomes functionally displaced a. Single click b. Reciprocal click 7. Disc becomes functionally dislocation a. Dislocation with reduction (i.e. catching) b. Dislocation without reduction (i.e. closed lock) 8. Retrodiscitis 9. Osteoarthritis Derangements of the Condyle-Disc Complex
  • 24.  If the morphology of the disc is altered and the discal ligaments become elongated, the disc is then permitted to slide (i.e., translate) across the articular surface of the condyle.  Alteration in the morphology of the disc accompanied by elongation of the discal ligaments can change this normal functioning relationship. In the resting closed joint position the interarticular pressure is very low. If the discal ligaments become elongated, the disc is free to move on the articular surface of the condyle. Because in the closed joint position the superior retrodiscal lamina does not provide much influence on disc position, tonicity of the superior lateral pterygoid muscle will encourage the disc to assume a more forward position on the condyle.  The length of the discal ligaments and the thickness of the posterior border of the disc will limit forward movement of the disc.  If the pull of this muscle is protracted, over time the posterior border of the disc can become more thinned  This is called as functional disc displacement.
  • 25. Characteristics of reciprocal click 1)During mandibular opening a sound is heard that represents the condyle moving across the posterior border of the disc to its normal position on the intermediate zone. The normal disc-condyle relationship is maintained through the remaining opening movement. 2)During closing the normal disc position is maintained until the condyle returns to very near the closed joint position. 3)As the closed joint position is approached, the posterior pull of the superior retrodiscal lamina is decreased. 4)The combination of disc morphology and pull of the superior lateral pterygoid allows the disc to slip back into the more anterior position, where movement began. This final movement of the condyle across the posterior border of the disc creates a second clicking sound and thus the reciprocal click.
  • 26.  As the disc becomes more flat, it further loses its ability to self-position on the condyle, allowing more translatory movement between condyle and disc.  The more freedom of the disc to move, the more positional influence from the attachment of the superior lateral pterygoid muscle.  Eventually the disc can be forced through the discal space, collapsing the joint space behind.  When this occurs, interarticular pressure will collapse the discal space, trapping the disc in the forward position.  Then the next full translation of the condyle is inhibited by the anterior and Medial position of the disc.  The person feels the joint being locked in a limited closed position because the articular surfaces have actually been separated, this condition is referred to as a functional dislocation of the disc Functional dislocation Vs functional displacement As previously described, a functionally displaced disc can create joint sounds as the condyle skids across the disc during normal translation of the mandible .If the disc becomes functionally dislocated, the joint sounds are eliminated because no skidding can occur.  Some persons with a functional dislocation of the disc are able to move the mandible in various lateral or protrusive directions to accommodate the movement of the condyle over the posterior border of the disc, and the locked condition is resolved. If the lock occurs only occasionally and the person can resolve it with no assistance, it is referred to as a functional dislocation with reduction. The patient will often report that the jaw "catches" when opening wide.
  • 27.  when person is unable to return the dislocated disc to its normal position on the condyle. The mouth cannot be opened maximally because the position of the disc does not allow full translation of the condyle .
  • 28.  Typically the initial opening will be only 25 to 30 mm interincisally, which represents the maximum rotation of the joint.  The person usually is aware of which joint is involved and can remember the occasion that led to the locked feeling. Because only one joint usually becomes locked, a distinct pattern of mandibular movement is observed clinically.  The joint with the functionally dislocated disc without reduction does not allow complete translation of its condyle, whereas the other joint functions normally. Therefore when the patient opens wide, the midline of the mandible is deflected to the affected side. The dislocation without reduction has also been termed a closed lock. Structural Incompatibility of the Articular Surfaces
  • 29.  Smooth articulation of the TMJ is ensured by two mechanisms: (1) boundary lubrication and (2) weeping lubrication.  If static loading continues for a prolonged time, however, weeping lubrication can become exhausted and sticking of the articular surfaces can result. When the static loading is finally discontinued and movement begins, a sense of stiffness is felt in the joint until enough energy is exerted to break apart the adhering surfaces.  This breaking apart of adherences can be felt as a click, and it denotes the instant return to normal range of mandibular movement  If however, the adherence remains for a significant period of time, fibrous tissue can develop between the articular structures ,and a true adhesion can develop. This condition represents a mechanical connection that limits normal condyle- disc-fossa function.  Another cause of adhesions is hemarthrosis (i.e., bleeding within the joint). The presence of blood by-products seems to provide a matrix for the fibrous unions found within adhesions.  Hemarthrosis can occur when the retrodiscal tissues are disrupted by either external jaw trauma or surgical intervention.  The morphologic characteristics of the surfaces usually conform to each other closely. If the morphology of the disc, condyle, or fossa is altered, joint function can be impaired. For example, a bony protuberance on the condyle or fossa may catch the disc at certain degrees of opening, causing alterations in function.  The disc itself may become thinned (as with disc displacement) or even perforated, causing significant changes in function.
  • 30.  These alterations in form can create clicking and catching of the jaw similar to that seen with functional disc displacements. Subluxation (hypermobility)  Some joint reveal that as the mouth opens to its fullest extent, a momentary pause occurs, followed by a sudden jump or leap to the maximally open position. This jump does not produce a clicking sound but instead is accompanied by more of a THUD.  The examiner can readily see it by watching the side of the patient's face. During maximum opening the lateral poles of the condyles jump forward (i.e., subluxation), causing a noticeable preauricular depression.  The cause of subluxation is usually not pathologic. Subluxation is more likely to occur in a TMJ with an articular eminence that has a short, steep posterior slope followed by a longer, flatter anterior slope. The anterior slope is often more superior than the crest of the eminence Spontaneous dislocation.
  • 31.  On occasion the mouth is opened beyond its normal limit and the mandible locks. This is called spontaneous dislocation or an open lock  With spontaneous dislocation the patient cannot close the mouth. Wide opening (e.g., from an extended yawn or a long dental procedure) almost always produces this condition.  Spontaneous dislocation typically occurs in a patient who has the fossa anatomy that permits subluxation. factors that Predispose to Disc Derangement Disorders  Steepness of the articular eminence: As the steepness increases, more rotational movement is required between the disc and condyle during forward translation of the condyle. Therefore patients with steep eminences are more likely to demonstrate greater condyle-disc movement during function.  Morphology of the condyle and fossa: Flat or gable like condyles that articulate against inverted V-shaped temporal components seem to have an increased incidence of disc derangement disorders and degenerative joint disease. It would appear that flatter, broader condyles distribute forces better, leading to fewer loading problems.
  • 32.  Joint: Some joints will show slightly more freedom or laxity than others. Some generalized laxity may be caused by increased levels of estrogen. For example, women's joints are generally more flexible and lax than men's.  Attachment of the superior lateral pterygoid muscle: it would be reasonable to assume that if the attachment of the muscle is greater to the neck of the condyle (and less to the disc), muscle function will have), correspondingly less influence on disc position. Conversely, if the attachment is greater on the disc (and less to the condyler neck), muscle function will correspondingly influence disc position more. Synovitis  Synovial tissues that lines the recess area of the joint become inflamed.  Characterised by constant intracapsular pain that enhances with joint movements. Capsulities  Capsular ligament becomes inflamed.  Tenderness when the lateral pole of the condyle is palpated.  Pain even in static position but joint movement generally increase the pain. Retrodiscities  Inflammation of retrodiscal tissues.  Constant dull aching pain that often increased by clinching.  swelling may occur and force the condyle slightly forward, down the Posterior slope of the articular eminence.  This sum can cause an acute malocclusion. Clinically such an acute malocclusion is seen as disengagement of the ipsilateral posterior teeth and heavy contact of the contralateral canines  As the disc is thinned and the ligaments become elongated, the condyle begins to encroach on the retrodiscal tissues. The first area of breakdown is the inferior retrodiscal lamina, which allows even more discal displacement. With continued
  • 33. breakdown, disc dislocation occurs and forces the entire condyle to articulate on the retrodiscal tissues.  If the loading is too great for the retrodiscal tissue, breakdown continues and perforation can occur. With perforation of the retrodiscal tissues, the condyle may eventually move through these tissues and articulate with the fossa. Arthritides.  Joint arthritides represent a group of disorders in which destructive bony changes are seen. Osteoarthritis: most common types of TMJ arthritides represents a destructive process by which the bony articular surfaces of the condyle and fossa become altered. It is generally considered to be the body's response to increased loading of a joints.  surface becomes softened (i.e., chondromalacia) and the subarticular bone begins to resorb. Progressive degeneration eventually results in loss of the subchondral cortical layer, bone erosion, and subsequent radiographic evidence of osteoarthritis.  Osteoarthritis is often painful, and jaw movement accentuates the symptoms.  Crepitation (i.e., grating joint sounds) is a common finding with this disorder. Osteoarthritis can occur any time the joint is overloaded, but it is most commonly associated with disc dislocation or perforation  Although osteoarthritis is in the category of inflammatory disorders, it is not a true inflammatory condition. Often once loading is decreased, the arthritic condition can become adaptive. The adaptive stage has been referred to as osteoarthrosis
  • 34.  Headache  Otologic signs and symptoms • ear pain • fullness in the ear or ear stuffiness • tinnitus (ear ringing) • vertigo (dizziness)
  • 35.  Management of TMDs and Occlusion. Jeffrey Okeson 5th edt.  Functional occlusion from TMJ to smile design. Dawson- 3rd ed.  Color atlas of TMJ surgeries. Peter Quinn.  DCNA 2007, Jan, vol 51, no. 1 -TMDs and orofacial pain  Temperomandibular disorders – Weldon Bell  TMDs an evidence based approach to diagnosis and treatment – Danial Laskin