Internal Derangement

Anatomy of the TMJ

1. Condyle and Eminence: The TMJ is a freely moving articulation between the condyle of the mandible and

the articular eminence of the temporal bone. When viewed laterally , the condyle is convex in an anteroposterior

direction .However , the eminence is also convex so, to achieve stability between these two articulating surfaces a firm but flexible structure ,the articulating disc ,is

present.

2. Articulating disc (Meniscus): The meniscus divides the joint into upper and lower

compartments or cavities ,it consists of :o anterior bando posterior band o intermediate zone

The disc has thick posterior and anterior bands ,and thin intermediate zone .

The contour of the disc with the thick bands helps prevent displacement of the disc from the condyle during translation.

3. Discal ligaments:The disc is attached to the condyle both medially and laterally by tight non-elastic discal ligaments ,which permit rotation of the disc across the condyle’s articular surface in anterior and posterior direction ,while restricting medial and lateral movements

4. Lateral pterygoid muscle:Consists of two separate muscles:

a. Inferior lateral pterygoid m .Origin: outer surface of the lat.pterygoid plate of the sphenoid bone.Course: runs backward ,upward and laterally.Insertion: anterior surface of the neck of the condyle.

b. Superior lateral pterygoid m. Origin: greater wing of the sphenoid bone .Insertion: anterior border of the articular disc + fuses with the inferior belly near its point of insertion.

5. Posterior attachment: Sometimes referred to as the retrodiscal tissue or bilaminar zone. It is attached anteriorly to the posterior band of the articular disc and posteriorly

to the tympanic plate and posterior aspect of the condyle forming the superior and inferior retrodiscal lamina.

It is highly vascularized and well-innervated tissue.

6. Articular capsule: Surrounding the TMJ is a thin fibrous C.T capsule that

defines the anatomic and functional bounderies of th TMJ.

The capsule is attached superiorly to the temporal bone and inferiorly to the neck of the condyle.

The synovial membrane secretes synovial fluid which provides the nutritional and metabolic requirements of the avascular articular surfaces and also acts as a lubricant between articulating surfaces during function.

7. Temporomandibular ligaments: The mandible is suspended from the temporal bone by two strong lateral

ligaments :a. Outer oblique portion , which limits inferior distraction of the condyle b. Inner horizontal portion , which limits posterior movement of the disc-

condyle complex. In addition accessory ligaments of the TMJ include:

a. Stylomandibular ligamentOrigin: styloid processInsertion: medial surface and border of the mandible at the angle.Function : limits excessive mandibular protrusion.

b. Sphenomandibular ligamentOrigin: spine of the sphenoid boneInsertion: lingula of the mandibleFunction: not significant

8. Vascular and nerve supply:a. Blood supply

By superficial temporal and maxillary a. derived from external carotid a.b. Nerve supply

Sensory and motor innervation primarily supplied by auriculotemporal n. derived from the mand.division of the trigeminal n.

Classification of temporomandibular disordersThe American Academy of Orofacial Pain[AAOP]has published a TMD classification system.1. Temporomandibular joint disorders

a. Deviation in form1. Articular surface defects2. Disc thinning and perforation

b. Disc displacements1. Disc displacement with reduction2. Disc displacement without reduction

c. Displacement of disc-condyle complex1. Hypermobility2. Dislocation

d. Inflammatory conditions1. Capsulitis and synovitis2. Retrodiscitis

e. Degenerative diseases1. Osteoarthrosis2. Osteoarthritis3. Polyarthritides

f. Ankylosis1. Fibrous2. Bony

2. Masticatory muscle disordersa. Acute

1. myositis2. reflex muscle splinting3. muscle spasm

b. Chronic1. myofacial pain2. muscle contracture3. hypertrophy4. myalgia secondary to systemic diseases

3. Congenital and developmental disordersa. Condylar hyperplasia f. Fracturesb. Condylar hypoplasiac. Aplasiad. Condylolysise. Neoplasms

Internal derangement This disorder is characterized by an abnormal relationship between the disc,

mandibular condyle ,and articular eminence. The disc most often displaced anteriorly or anteromedially , but medial ,lateral

and even posterior displacements have also been reported. Therefore ,in order for a disc displacement to occur ,there must be elongation of

the disc attachments and deformation or thinning of the posterior border of the disc that allows the disc to slide anteriorly or anteromedially on the condyle

In healthy joint ,the posterior band of the disc ends at the apex of the condyle when the teeth are in occlusion.

Varieties of internal derangement:

1.disc displacement with reductionDefinition:

Refers to the stage in which the disc is displaced in an anterior or anteromedial position upon closing and returns to a more normal position relative to the condyle on opening.

Secondary masticatory muscle activity often accompanies a disc displacement, causing pain and limited mandibular opening.

Clinical signs and symptoms:

1) Clicking and popping sounds during mandibular opening and closing , this dual opening and closing noise is often referred to as reciprocal clicking and represents disc displacement on closing and disc reduction on opening.

2) Deviation of the mandibular midline to the side of the affected joint on early opening ,This results from the temporary arrest in translation caused by the displaced disc when reduction of the disc occurs , condylar translation becomes normal and the mandible returns to a corrected position.

NOTE: The term deviation must be differentiated from deflection. Deviation:

An initial discursive movement of the mandible away from the midline ,the mandible returns to the centered position at the end of the movement

Deflection: Mandibular midline is continously displaced to the affected side and does not return to a centered position

In conclusion:

Deviation is a characteristic finding of anterior disc displacement with reduction , while deflection is a prominent feature of anterior disc displacement without reduction.

3) Pain may accompanies ADD with reduction ,due to strained discal ligaments or from condylar pressure against the posterior attachment.

4) Mandibular range of motion is usually normal and , in fact, the amount of vertical opening may be greater than normal. If there is limited opening, it is usually the result of secondary muscle splinting because of joint pain , not mechanical obstruction by the disc.

2. disc displacement without reductionThis condition characterized by displacement of the disc on closing followed by a failure to reduce or recapture the disc during translation .The condyle is unable to pass under the displaced disc because of a thickening of the posterior band, and a decrease or loss of tension in the posterior attachment.This results in limited condylar translation in the affected joint and the disorder is often referred to as {closed lock}

Clinical signs and symptoms:1) The most obvious clinical sign is a severely restricted opening of a maximum of

25 to 30 mm.2) Mandibular midline sharply deflected to the side of the involved joint3) Protrusive and lateral excursion is also limited.4) It is usually painful due to inflammation in the articular capsule , posterior

attachment , or discal ligaments5) Muscle activity of the temporalis and masseter on the affected side is usually

increased6) Joint noise is absent , but as the displacement becomes chronic , degenerative

changes may occur in the articular surfaces causing crepitus.Note:

Because a limited range of motion can also be symptomatic of elevator muscle spasm ,a differential diagnosis is necessary to determine the cause of restriction .In general, contraction of an elevator muscle resticts only vertical opening and does not significantly affect lateral or protrusive excursions ,while non-reducing displaced disc, will usually affect all codylar translation affecting opening ,protrusive and lateral excursions.

IN LATE STAGES:Perforation may occur with degenerative changes of the condyle.

Normal and Abnormal Menisci

Normal (31K) Anteriorly DisplacedWith Reduction (39K)

Anteriorly DisplacedWithout Reduction

(37K)

Examination of TMD patient Screening for TMD should be an essential part of routine dental &medical examination.

A. HISTORY TAKING

1. Personal data: name ,age ,date ,doctor’s name , referral.

2. Chief complain:Consist of 1 or more symptoms causing the major discomfort or dysfunction .Each symptom should be listed in order of importance to the patient ,because success in treatment means elimination or reduction of these symptomsShould be recorded in patients own words.

3. History of present illness: This include the onset , location ,frequency ,intensity &quality of each complain.

4. Medical history:Includes:

past hospitalization. past allergies. past illness. past accidents past &current medication any other existing disorder.

5. Personal and family history:Information regarding patients education, occupation ,marital status ,number of children ,and health of family members may infleunce diagnosis and management.An inquiry of the patient’s social and economic status should be made because of its possible infleunce on management.

6. Dental history:a) we should note:

Any history of trauma to the dentition , face or jaws Orthodontic treatment Extensive restoration If the patient has a removable prothesis , he or she should indicate the no. of hours.

b) Parafunctional &occupational habits: Grinding Clenching Nail biting Gum chewing Mouth breathing

7. Review of system:This focuses the attention of the patient and the clinician on the whole patient and helps in determining the effects of any systemic problem on the patients symptoms.Example:

Cardiovascular neg ( ) pos ( ) GI/liver neg ( ) pos ( ) Musculoskeletal neg ( ) pos ( ) Endocrine neg ( ) pos ( ) Genitourinary neg ( ) pos ( ) Neurologic neg ( ) pos ( ) Respiratory neg ( ) pos ( )

B. COMPREHENSIVE PHYSICAL EXAMINATION

1. Head and neck evaluation:Head and neck palpation to identify any hypersensitive areas or trigger point.Examination of lymphnodes (submental ,submandibular ,superficial cervical chain) to determine the presence of either:

Lymphadenitis indicates the presence of localized area of infection Lymphadenopathy may represent a metastatic neoplasm or a chronic

fibrotic nodule from past infections.Evaluation of salivary glandFacial evaluation to identify any :

Facial asymmetry Ramus height Facial type(class1 ,class2 ,class3 )

2. TMJ evaluation:

a) Mandibular range of motion:The following movements should be measured:

Opening Lateral excursion Protrusive excursion

All movements should be preformed to the maximum range and any patient report of pain or joint noise should be noted.

Opening: Average interincisal opening ranges from 40 to 55 mm. Active range of motion (AROM)is measured from the incisal edge of the

max. central incisor to the incisal edge of the mand. Central incisor ,the amount of overbite or open bite should be added or subtracted respectively.

During opening and closing any deviation or deflection should be noticed.

Protrusion: Measured by asking the patient to protrude his or her mandible straight ahead

starting from a relaxed , slightly open position. Before performing this movement , the overjet should be measured with the teeth

lightly occluded & added to the distance the mand. Incisors travel past the max.central incisor.

Lateral excursion: Evaluated by having the patient move the mandible to one side as far as possible

and then to the other side. A reference mark may be made on the patient’s max. & mand. Incisors.

b) Joint soundsJoint sounds are usually examined with a stethoscope placed over the lateral wall of each TMJ as the patient’s moves through the range of mandibular motion.Most commonly heard sounds are:

Click single noise of short duration usually associated with disc displacement.

Crepitus grating or gravelly noiseThey can be classified according to the point in the translatory cycle where they occur:

Early opening /late closing (0 to 15 mm) Middle opening /middle closing (16 to 30mm) Late opening/early closing ( 31 to 50 mm)

c) Joint palpationPalpation of the TMJ is done in the periauricle area or through external auditory meatus.When grading tenderness or pain on palpation the following scale is used:

0 = no pain 1 = mild pain 2 = moderate pain 3 = severe pain

3. Muscle examinationThese muscle should be examined for any tenderness to palpation: Temporalis (anterior ,middle ,posterior ,insertion) Masseter (origin ,belly ,insertion) Medial pterygoidThe following scale is used to identify the degree of response: 0=no pain 1=mild pain 2=moderate pain 3=severe pain *=trigger point

The following criteria should be taken while examining the muscle: Muscles should be evaluated through out its length Muscles should be evaluated at rest and contracted position Muscles should be examined bilaterally. Muscles should be palpated both horizontally and parallel to their

attachments.

4. Intraoral examinationAll teeth should be checked for active caries ,broken restoration ,cracks ,sensitivity and mobilityHygiene and periodontal status should be evaluated.Soft tissue evaluation include: Visualization and palpation of the lips and oral mucosa Any alteration in soft tissue color ,contour, or texture should be noted. Areas of ulceration ,abrasion ,inflammation or hyperemia Cheek biting is indicated by rough irregular buccal mucosa. Clenching is indicated by tongue scalloping.Salivary gland function should be evaluated.Classify the patient’s facial type according to Angle’s classification ,this will help in determining the type of treatment needed.Any cross bites , open bites , and deep overbites is noted.Detect any protrusive ,lateral or non-working side interferences.Detect wear facets as it is an indicator of parafunctional activity

C. RADIOGRAPHIC DIAGNOSIS

1) Plain radiography:Are able to show changes in bone only and cannot visualize meniscus.

2) Panoramic x-ray (orthpantomogram):Panoramic radiography can provide adequate screening images of the TMJs ,mandible ,maxilla ,maxillary sinuses ,as well as teeth and periodontium in one radiograph .This type of screening can be used to evaluate gross bony changes such as tumors ,fractures or asymmetries.As with any of the imaging techniques ,there are limitations such as magnification ,superimposition ,and image with little sharpness.

3) Tomography:Tomograms are views of preselected plane of joint anatomy, from 0.5 to 10mm thickness , produced by synchronous movement of the x-ray source and the film during exposure . With this technique, several “slices” or images can be made through the joint.The major advantage over plain films:

clear images are provided elimination of superimposition

4) TMJ MR Magnetic resonance (MR) , it is a new medical imaging procedure with vast clinical potential , offers detailed views of internal anatomy without ionizing radiation or invasion.It is more superior than C.T scan in visualizing the soft tissues but inferior than it , in detecting bony changes.

Normal TMJ MR showing normal meniscus (m) posterior and superior to condyle (C) -- the articular eminence (E) and auditory canal (AC) are also show

In internal derangement, the meniscus is abnormally positioned anterior to the condyle.

Displaced meniscus (arrows, m) anterior to the condyle (C) and auditory canal (AC) and beneath the articular eminence (E)

Static images taken at maximum intercuspation

Case 1

Dynamic MRI sequence of a TMJ of a 25-year old patient with an anterior

Case 2

Dynamic MRI sequence of a TMJ of a 22-year-old female patient with an

Case 3

Dynamic MRI sequence of an opening/closing movement of a normal TMJ of

Case 4

Dynamic MRI sequence of the TMJ of a 50-year-old male patient with a

disc displacement with reduction. The clicking occurred in the late stage of mouth opening. Notice how the disc is pushed past the eminence, where it bends into a U shape. Then the disc-condyle relationship is reduced while the bent disc returns to its normal shape.

anterior disc displacement without reduction. During opening the mobile disc is pushed ventrally by the condyle.

a 38-year-old male subject. The harmonious movements between condyle and disc are clearly visible. Notice also some bending of the disc at the end of the opening.

chief complaint of crepitation. The static images of this patient show clearly the irregular bony surfaces of both the condyle and the eminence. An area of low signal cranially and dorsally to the condyle is visible. During condylar movement this structure moves ventrally together with the condyle. Notice also the area of high signal (joint fluid) ventrally and cranially to the condyle.

Case 5

Dynamic MRI sequence of a TMJ of a 20-year-old male patient with an anterior disc displacement without reduction. During opening

Case 6

Dynamic MRI sequence of a 19-year-old female patient with an anterior disc displacement with reduction. The disc is located under

Case 7

Dynamic MRI sequence of a TMJ of a 24-year-old female patient with an anterior disc displacement with reduction. Notice that the patient needs 3

Case 8

Dynamic MRI sequence of a 19-year old female patient with an anterior disc displacement with and without reduction, ie,

the ventral part of the disc hardly moves, while the dorsal part tends to bend by moving ventrally. The sequence suggests that the disc is stuck.

the eminence. Notice how during the initial opening the disc bends caudally to a U shape. Suddenly, the disc springs dorsally to a reduced position. At the end of closing the disc is again in its initial position under the eminence.

movement phases to fully open the mouth. In the first phase there is some translation, followed by a rotary movement and dorsal translation. The disc is not reduced. In the second phase the disc is reduced. The sequence stops with the condyle under the eminence. Finally, the condyle translates and rotates ventrally to the eminence.

with occasional locking. The sequence demonstrates the full opening path with disc reduction (first cycle) and without reduction (second cycle). In the sequence without reduction, the disc is pushed ventrally and caudally without bending.

5. TMJ CT Computed tomography is a non-invasive technique.Helpful in diagnosis of abnormalities in hard and soft tissue component of joint.The patient is scanned in either the transverse or direct sagittal plane using thin sections (1-2 mm) and a soft tissue technique.

Normal TMJ CT showing normal disk posterior and superior to condyle (C).

Displaced meniscus (arrow) anterior to the condyle

6. TMJ Arthrography A 25 or 23 gauge needle is placed into the inferior joint space immediately posterior to the condyle. Small amounts of iodinated contrast are injected under fluoroscopy. The contrast tracks along the posterior, superior and anterior portions of the condyle. The anterior collection of contrast, called the anterior recess, normally has a smooth, tear-drop shape.

If the meniscus is perforated, contrast flows into both the superior and inferior joint recesses. However, the arthrographic needle can inadvertently puncture the meniscus and cause iatrogenic filling of both joint spaces.

QuickTime movies ofJoint Injections

Normal InferiorJoint Space (11K)

Perforated Meniscus (13K)

As the condyle translates anteriorly, the contrast usually empties from the anterior recess and flows posteriorly.

When the meniscus is anteriorly displaced, the anterior recess becomes abnormally elongated. Often the displaced meniscus is deformed or buckled, which results in a mass effect against the contrast in the anterior recess. As the condyle translates anteriorly, the mass effect against the anterior recess often increases. When the meniscus reduces, the anterior recess returns to a normal appearance.

If the meniscus does not reduce, the anterior recess remains deformed in the fully open mouth position.

QuickTime movies ofTMJ Arthrogram

Normal Joint (30K) Anteriorly DisplacedMeniscus with

Reduction (32K)

Treatment of TMD & Internal derangement1) Patient education.2) Physical therapy.3) Pharmacological therapy (medication).4) Occlusal therapy.5) Surgical approach.

1) Patient education:Patient education is very important in order to modify the patient's behaviour and therefore a brief description of the mechanism of internal derangement should be given.A well informed patient could play a major role in the treatment since the

disorder is of biomechanical nature Therefore the patient should be instructed to eat softer food in order to decrease loading of the joint.The patient should also be informed about the disorders natural course and treatment so that reasonable expectations can be met

2) Physical therapy:

Physical therapy includes both pain reducing and function improving management.Some of the most common techniques for the management of acute and chronic TMJ-pain is the use of :

Moist heat and coolant therapy in form of hot moist towels, ice cubes and different vapour spray containing ethylchloride or fluoromethane.

Transcutaneous nerve stimulation and acupuncture. In order to avoid hypomobility and muscle atrophy , associated with TMD the patient should be instructed to perform different jaw exercises so that normal ranges of movement can be regained.Acute permanent disc displacement that have occurred in less than a week may in some cases be successfully treated by joint distraction which means that the clinician places a downward force on the patients lower second molar for several

seconds. This procedure might be repeated if necessary and if the disc is successfully reduced , an anterior repositioning appliance should be used. Discs that have been displaced for more than a week are not likely to benefit from this method .

3) Medications for TMD (Pharmacology)MEDICATIONS can be very effective to reduce pain and inflammation. The extended use of narcotic (oploid) medications such as:

Codeine Hydrocodone Propoxyphene sedative psychotropic drugs such as :

Valium, Xanax, and Ativan may lead to depression, drug tolerance and addiction.

Use of these medications which often give temporary relief from pain, are discouraged for long term pain management.The most effective drugs for TMD management include:

Non-narcotic analgesic drugs such as :Acetaminophen (Tylenol). Non-steroidal anti-inflammatory drugs (NSAIDS) such as: Aspirin,

Trilisate, Ibuprofen, Naproxen and prescription strength NSAIDS. Muscle relaxant drugs such as: Carisoprodol (Soma) and Cyclobenzaprine

(Flexeril). Tricyclic anti-depressant medications such as : Amitriptyline (Elavil),

Nortriptyline (Pamelor), and Doxepin (Sinequan). All medications have specific benefits and side effects. Long term use of medications should be directed and supervised by your dentist or physician to reduce the potential side effects.

4) Occlusal therapyThere are mainly two types of basic approaches to occlusal appliance therapy for the treatment of internal derangement. For patients with anterior disc displacement or degenerative joint disease the flat occlusal splint is to be worn in order to :

unload or reduce the force placed on the TMJ area. reduces muscle hyperactivity.

The anterior repositioning splint has been proposed for the treatment of displaced discs with reduction.

The splint is designed so that it will give an anterior ramping effect forcing the mandible into a protruded position so that the disc will be recaptured to a correct anatomical position. After symptom relief ,permanent occlusal modification should be performed in order to gain a lasting effect,

Treatment may include occlusal equilibration, prosthetic restoration and orthodontics

5) Surgical approach:The most common surgical approaches to the TMJ are post and pre auricular.Each one of these techniques has certain advantages but the preauricular apprach is the most favourable cause it minimize the risk of damage to the temporal branch of the facial n. & to auriculartemporal n. while preserving facial cosmetics.It has been estimated that between 10-20 % of the patients have symptoms inspite of non-surgical treatment and in these cases surgery may be considered.Principally, there are several methods, so which one of these methods to use is based on the pathology within the joint .

I. Arthrotomy (open-joint surgery)

a) Disc repositioning:The disc repositioning procedure was first described by McCarty and Farrar.They recommended removal of tissue from the bilaminar zone in an amount that corresponded to the degree of the disc displacement.the disc should then be repositioned over the condyle and sutured to the distal and the collateral ligaments.Clinical studies demonstrated a favourable outcome in terms of decreased pain and improved mandibular function in 80% to 94% of the patients.However, it has been difficult to maintain the disc repositioned postoperatively.

b) Modified Condylotomy:Is a modification of the intraoral vertical ramus osteotomy used in orthognathic surgery.The aim of this procedure is to reposition the condyle anteriorly and inferiorly beneath the displaced disc.This will result in a slight increase in the joint space, which will allow the disc to move to a more favourable position.A study conducted on 400 patients over a 9-year period found good pain relief in about 90% of the patients treated with this method.

There seems to be a limitation with both disc repositioning & modified condylotomy,since the operation has to be performed in very early disease-stages when the disc is still in a good condition.

c) Discectomy:It is total removal of the articular disc and its accompanying soft tissue attachments.This procedure is generally performed when the disc is damaged beyond the point of repair.

Following discectomy, the disc may not be replaced ,allowing the condyle to function directly with the glenoid fossa.

Discectomy without replacement has been evaluated according to the success criteria established by the American Association of Oral and Maxillofacial Surgeons (AAOMS) in 1984:1. No pain or so mild.

2. Range of motion greater than 35 mm for vertical and greater than 6mm protrusive and lateral excursions.

3. Regular diet , avoid hard foods.

4. No radiographic changes

5. Absence of significant complications.

However ,the method has also been criticised claiming that discectomy without replacement eventually will lead to osteoarthritisAs a result some surgeon choose to replace the articular disc with an autogenous or allogenous graft.

Alloplastic implants :The alloplastic implants that have been used are silicon , Proplast-Teflon and metal.

Silicon:Silicon was initially regarded as successful due to its ability to avoid postoperative fibrous adhesion and to stimulate rebuilding of the articular surfaces.

It was later found that silicone have a high coefficient of friction and poor wear characteristics under functional load (Eriksson L, Westesson P-L) which will cause abradation and loss of particles from the implant that eventually will disperse into surrounding tissue causing reactive synovitis

In 1985 Eiken et al proposed that digestible silicone material may be phagocytized by macrophages resulting in secretion of neutral proteinases that are likely to produce bony resorption and cyst formation. Foreign-body giant cell reaction has also been reported.

Proplast-Teflon:

Choung and Piper proposed the use of Proplast-Teflon implants in order to prevent adhesion and ankylosis.

but it was later shown in several studies that the material produced severe destructive osseous changes and lymphadenopathy .

Due to these obvious disadvantages both Silicone and Proplast-Teflon implants were removed from the market in 1993.

Metal:The metal implants were first introduced by Robinson in 1960 to prevent ankylosis after discectomy. A 14-year follow up study performed by House et Al in 1984 showed that the bone under the implant and on the condyles were covered by fibrous connective tissue. House proposed that the use of metal implants would result in minimal bony changes in the joint, however there is a lack of experimental data supporting this thesis.

Autogenous implants :Because of the complications that have been related to the use of Silicon and Proplast-Teflon a replacement material has been sought that is autogenous. The search has mainly been focused on dermal grafts, cartilage grafts and temporalfascial and muscle grafts. The use of dermal graft have been proposed by several authors to be suitable for repair or replacement of the articular disc and god results have been reported .There are on the other hand authors that have described vascular perfusion and forming of inclusion cysts to be associated with the method and due to these obviously divergent opinions further documentation is needed before the material can be recommended .Auricular grafts does not seem to be an ideal disc replacement material due to difficulties in stabilisation of the graft which have resulted in development of degenerative changes within the joint because of graft displacement .Temporalis muscle and fascia graft has proven to be beneficial by preventing ankylosis. The graft is also easily obtained from a local donor area through the same incision used to access the TMJ. But in spite of these obvious advantages it has been shown that the material is unable to withstand functional loading why the graft cannot be regarded as a suitable disc replacement material .

In contrast to these rather poor results concerning disc replacement materials for the TMJ the best option so far seems to be discectomy without replacement

d) Total joint replacement

II. Arthrocentesis:Consists of anesthezing the affected TMJ with local anaesthetic followed by flushing the joint with a sterile solution such as Lactate Ringers solution.Used to lubricate the joint surfaces and reduce inflammation.Gentle manipulation of the jaw is often utilized following Arthrocentesis to improve the jaw range of motion.

III. Arthroscopy:Is a telescope – like (endoscope) instrument that is placed in the upper TMJ space through a small incision directly infront of the earUses:

Diagnostic Enables the operator to view the joint space to detect causes of

pain and dysfunction(direct observation) Photographic and video documentation Sampling of the joint tissue for biopsy.

Operative(corrective) Lysis ,lavage and manipulation Anterior disc releasing procedures Disc-stabilization procedures Surgical debridement

EtiologyTemporomandibular disorders are classified into several subgroups depending on its etiology, which is often multifactorial and difficult to determine.

The four major causes that are most likely to be involved are:1. Macrotrauma2. Microtruma 3. Arthrotic/arthritic disease 4. Occlusal factors.

1. Macrotrauma:Macrotrauma to the TMJ can occur from either impact or overstreching as a result of fractures, joint contusion, whiplash incidence or iatrogenic injuries during dental and surgical treatment. These conditions may lead to an impaired function and eventually to an internal derangement. Katzberg et al 1980 reported that 22 of 89 patients (25%) with arthrografically proven internal derangement had a history of jaw trauma immediately prior to the onset of their TMJ problem .

2. Microtrauma: Microtrauma can occur from repetitive behaviours such as:

Chronic clenching Bruxism Atypical chewing habits Nail biting.

3. Osteoarthritis :Osteoarthritis and internal derangement seems to be strongly related and may be explained as follows.

Cartilage breakdown affects the sliding properties of the joint surfaces that give rise to friction and adhesive wear resulting in disc hesitation. This may induce joint stiffness and repetitive stretching of the disc attachments. The attachment may gradually elongate to an extent that will result in a disc displacement .

osteoarthrosis rather than its cause.

4. Occlusal factors:Occlusal factors such as :

Class 2, division 2 malocclusions, Loss of molar support and Any occlusal contacts that may deflect the condyle posteriorly have also

been suggested as factors of importance.Farrar and McCarty 1980 proposed that the retentive phase in orthodontic treatment is a cause.

For example :During retention the typical patient have anterior retainers that maintain the proper relations between the anterior teeth. The posterior teeth settle, allowing the lower anterior teeth to occlude hard on the lingual surfaces of the upper teeth. This causes the condyle to be displaced posteriorly and initiate disk displacement.

However, Katzberg et al recently performed a study on patients who had previous history of orthodontic treatment and found no association with the presence of internal derangement