TMJ Anatomy & Problems

By : Dr.Mustafa Kareem

B.D.S

is a bi-arthroidal hinge joint that allows the complex movements necessary for eating, swallowing, talking and yawning.

TEMPOROMANDIBULAR JOINT

Other synonames-:“Craniomandibular Joint”

a diarthrodial or synovial lined joint

A compound joint: > 2 components

•Temporal Bone

•Mandibular Condyle

•Articular Disc (functionally the articular disc served as a nonossified bone)

A) Temporal Bone-:

• Cranial component• Mandibular fossa• Articular eminence• Articular surface from superior fossa to the anterior aspect of the eminence , thickest bone .

B. Mandibular Component:Condyle

• Condylar dimensions: A-P 8-10 mm M-L 15-20 mm• Articular surface: Anterior superior aspect•Variation side to side and shape is common. Response to loading• Lateral pole anterior to medial pole .

C. Articular Disc

The articular disc is a fibrous extension of the capsule

Retrodiscal tissue - Unlike the disc itself, the retrodiscal tissue is vascular and highly innervated.

D. TMJ Capsule

Function: 1) resist any medial , lateral or inferior forces that tend to separate or dislocate the articular surface2) confines synovial fluid 3) joint proprioception

The capsule is a fibrous membrane that surrounds the joint and attaches to the articular eminence, the articular disc and the neck of the mandibular condyle.

E.LigamentsThe ligaments give passive stability to the TMJ.

Limits: retrusion and inferior condylar distraction

Temporomandibular Ligament

is the thickened lateral portion of the capsule, and it has two parts, an outer oblique portion and an inner horizontal portion.

runs from the styloid process to the angle of the mandible

runs from the spine of the sphenoid bone to the lingula of mandible.

The stylomandibular ligament

The sphenomandibular ligament

limits excessive protrusive movements of the mandible

are the discomalleolar ligament (DML), which arises from the malleus (one of the ossicles of the middle ear) and runs to the medial retrodiscal tissue of the TMJ, and the anterior malleolar ligament (AML), which arises from the malleus and connects with the lingula of the mandible via the sphenomandibular ligament.

The oto - mandibular ligaments

Muscles and Jaw Movement

Movements of the Temporomandibular joint

Movements MusclesElevation (close mouth) Temporal, masseter medial pterygoid

Depression (open mouth) Lateral pterygoid and supra-infrahyoid

Protrusion(protruded chin) Lateral pterygoid, masseter medial pterygoid

Retrusion (retruded chin) Temporal(posterior oblique and near horizontal fibers) and masseter

Lateral movements Temporal of the same side,pterygoid(grinding and chewing) of the other side and masseter

TMJ innervation

Sensory innervation of the temporomandibular joint is derived from the auriculotemporal and masseteric branches of V3 (otherwise known as the mandibular branch of the trigeminal nerve). These are only sensory innervation. Recall that motor is to the muscles.

TMJ Blood supplyIts arterial blood supply is provided by branches of the external carotid artery, predominately the superficial temporal branch . Other branches of the external carotid artery namely: the deep auricular artery, anterior tympanic artery, ascending pharyngeal artery, and maxillary artery may also contribute to the arterial blood supply of the joint.

TMJ Problems

The Articulatory System

The Articulatory System is comprised of three components: the temporomandibular joints, the muscles of mastication and the occlusion (the nature contact between the upper and lower teeth). Or to use an engineering analogy, the hinges, the motors and the contacts.

Etiology of TMDsThe relationship of occlusal disharmony and TMDs become a focus after Costen (1934) report

Lack of clear signal cause has resulted in the proposal of a multifactorial etiology .

Parafunctional habits

Emotional distress

Acute trauma

hyperextension

Instability of maxillomandibular relationships

Laxity of the joint

Poor general health and lifestyle

Co-morbidity of disorders

Classification of TMDs:TMDs can be broadly classified into masticatory disorders or TMJ dysfunction syndrome and TMJ disorders

AnkylosisAdhesionFibrosis of musclur tissueCoronoid elongation

Congenital & DevelopmentalMuscle Hyper/atrophy NeoplasiaCondylar hypo/hyperplasia

Disk-condylar incoordinationDisk-condylar restrictionOpen Dislocationosteoarthritis

Myofasial painMyositis Spasm

Maxillomandibular Disorders Mandibular mobility Disorders

TMJ Disorders Masticatory Muscle Disorder

Examination of TMJJoints

We will examine...

Pain in or in front of the ear is a common reason for a patient to seek treatment. A tenderness to palpation implies inflammation, generally as a result of acute or chronic trauma.A finger should be placed in the immediate pre-auricular area, gently applying pressure on the lateral pole/head of the condyle while the jaw is closed. The level of pain and discomfort on each side should be assessed and compared.The little finger should also be placed in the external auditory meatus, and pressure gently applied forwards.

1 )TENDERNESS TO PALPATION

JOINT SOUNDS

There are 2 types of joint sound to look out for:•Clicks - single explosive noise•Crepitus - continuos 'grating' noise

ClicksA joint click probably represents the sudden distraction of 2 wet surfaces, symptomatic of some kind of disc displacement

CrepitusCrepitus is the continuous noise during movement of the joint, caused by the articulatory surfaces of the joint being worn. This occurs most commonly in patients with degenerative joint disease.

The joint sounds should be listened to with a stethoscope, preferably a stereo one, as the two sides can be more easily compared.

This is the only truly measurable parameter, as the others are more subjective

Movements to be measured are:•Incisal opening - pain free limit•Incisal opening - maximum (forced)•Lateral mandibular excursions•Mandible deviations on pathway of opening

Incisal openingThe incisal opening is measured from the upper incisal tip to the lower, with the patient first of all opening to the limit of their comfortable, pain free range. This is then compared to the normal range of motion (see right). Their maximum (forced) limit is also recorded. It is important to determine whether a limitation of vertical movement is due to pain or a physical obstruction. If it is pain, then it may be a muscular problem, if an obstruction, then disc displacement is most likely.

3 )RANGE OF MOTION

Lateral ExcursionsThe lateral movement should be measured from mid-line to mid-line, the patient moving the mandible to their maximum extent, from one side to the other.

Mandibular deviationWhen the jaw is opened, the path it follows should of course be straight and consistent. Deviations from the normal are either lasting or transient, and are all suggestive of internal derangements of different sorts.

Lasting deviationsLasting deviations are caused by the joint on one side not moving as far as on the other. If the movement is consistent but off centre(i.e. a straight diagonal pathway), this may due to adhesions within the joint. If the movement is normal till just before the maximum range, when a lateral deviation occurs, this may be due to anterior disc displacement without reduction (if the overall range of opening is reduced).

Transient deviationsTransient deviations occur when the joints are moving as far but at different rates. This is often caused by disc displacement with reduction.

Masticatory Muscle Examination

Masseter

Temporal is

Medial pterygoid

Lateral ptergoid

Intra oral examination

To see signs of parafunction such as cheek or lip biting, accentuated linea alba , scalloped tongue borders , occlusal wear , tooth mobility , generalized sensitivity to percussion due to chronic trauma by biting , multiple fracture of enamel and restoration .

TMJ Disc displacementDisk Displacement Without ReductionThis occurs when the ligaments are stretched more and the disk slips too far out of position so that it can no longer “click” back into place. It then acts like a door-jam and blocks the normal movement of the joint. As the mouth opening is limited it is also called “locked jaw” even though typically a person can still open to two-finger widths.

 When the disk is positioned forward there is increased load onto the painful and compressible retrodiscal tissues which can lead to increased TMJ/ear pain, deviated mouth opening, bite changes and osteoarthritis.

Acute jaw locking episodes can usually be unlocked using manual jaw manipulation and oral splints. If the locking is left untreated then the disk displacement becomes chronic as there are more permanent anatomic changes within the TMJ.

Treatment usually consists of medications, jaw exercises, manual jaw manipulation, oral appliance therapy and minimally invasive arthroscopy.

Disk Displacment With Reduction

The jaw will “click” or “pop” when the ligaments that hold the disk in place become stretched thereby allowing the disk to slip forward (and usually either medially or laterally). As the mouth opens the lower jawbone begins to slide forward and this causes the disk to “click” or “pop”.

The jaw will usually curve or deviate to the affected side during mouth opening. Pain can vary from none to severe. Often the musculature of the jaw and neck will tighten up leading to headaches, facial pain and neck pain. As the condition worsens patients will typically notice a “catching” sensation where they have to shift their jaw to open or close normally. Patients will also at times notice a feeling of their bite shifting and feeling off. If this is left untreated it will often progress to jaw locking and degenerative changes.

Treatment will typically consist of medications, jaw exercises, manual jaw manipulation, oral appliance therapy, and in a minority of cases (approximately 5%) minimally invasive TMJ arthroscopy. Referrals to physical therapy, massage therapy.

TrismusMay mean reduced opening of the jaws caused by spasm of the muscles of mastication, or it may generally refer to all causes of limited mouth opening

Temporary trismus is much more common than permanent trismus, and may be distressing and painful, and limit or prevent medical examination or treatments requiring access to the oral cavity.

Identifying Trismus

The 3 Finger Test

A quick and easy way to identify a possible case of Trismus is to place three of your fingers, stacked, between your upper and lower teeth, or dentures. If the mouth can open wide enough to accommodate them comfortably, then Trismus is unlikely to be a problem. If not, this may indicate Trismus or its development that should be further investigated by a clinician.

causesIntracapsular causes :1)Infective arthritis2)Juvenile arthritis3)Traumatic arthritis4)Intracapsular condylar fracture.

Pericapsular causes:1)Irradiation 2)Dislocation3)Condylar neck fracture4)Pericoronitis

Muscular causes:1)TMJ dysfunction syndrome2)Heamatoma from IDB3)Tetanus

Other:1)Oral submucous fibrosis2)Systemic sclerosis3)Zygomatic and maxillary fractures4)Drugs such as Phenothiazine neuroleptics and Metoclopramide

With mild pain and dysfunction (the patient reports minimum difficulty opening his or her mouth)

Heat therapy consists of applying hot, moist towel to the affected area for approximately 20 min every hour.

Warm Saline Rinse:a teaspoon of salt is added to a 12 ounce glass of warm water and held in the mouth on the involved side (and spit out) to help relieve the discomfort of trismus.

Muscle Relaxant: Diazepam (approximately 10 mg bid) or other benzodiazepine is used if deemed necessary

Analgesic:

Aspirin (325 mg) is usually adequate as an analgesic in managing pain associated with trismus. Its anti-inflammatory properties also are beneficial. On rare occasion, Codeine may be necessary (30 to 60 mg q6h) if the discomfort is more intense

Physiotherapy:

The patient should be advised to initiate physiotherapy consisting of opening and closing the mouth, as well as lateral excursions of the mandible for 5 min every 3-4 hours. Chewing gum (sugar free) is yet another means of providing lateral movement of the TMJ.

Myofacial Pain Dysfunction Syndrome MPDS

Myofacial pain has been characterized by muscle pain that radiates or referred when the muscle is stimulated during palpation examination.

In case of MPDS , the altered muscle movement sometime restricted and sometime involving deviation of the midline of the chin on mouth opening.

Etiology of MPDS

MPDS

Myospasm

Altered chewing pattern

Muscular Overcontraction

Muscular Overextention

Muscular Fatigue

Muscular HyperactivityStressDental

irritation

Diagnosis of MPDS

Pain of unilateral origin is the most common symptom.

Masticatory muscle tenderness

Limitation of the mandibular movement

A clicking or popping sound in the TMJ

Management of MPDSThe management was achieve according to the cause , if the cause was malocclusion the management accomplished by :

1) Occlusal adjustment (Orthodontic treatment).2) Prosthodontic treatment.3) Orthognathic surgery.

But if the cause was due to parafunction that related to stress and other psychological problems such as anxiety and depression , the management accomplished by :

1)Occlusal splint

2)Electronic Biofeedback treatment (such as electromyography biofeedback by use of sleep alarm or electrical stimulations)

3) Physical therapy ( such as transcutaneous electrical nerve stimulation (TENS) and low level laser )

4) Drugs therapy such as muscle relaxant, antidepressent ,and antianxiety)

5) Psychological treatment

6) Surgical interventions (Myosurgery such as decrease the muscle fibers)

TMJ Dislocation

The TMJ may become fixed in the open position by anterior dislocation , this due to :

Forcible opening of the mouth by a blow on the jaw or during dental extractions under general anaesthesia. Occasionally a patient will dislocate spontaneously whilst yawning. Epileptic patients sometime also dislocate during fits.

Occationally the dislocation remains unnoticed and a patient may tolerate the disability and discomfort for weeks or even months

Management

Given 10 mg of diazepam I.V

Pushing the mandibular downwards and backwards

Recurrent Dislocation is more common (typical feature of flobby joint syndrome) , Augmentation of the eminence by bone graft or down fracture of the eminence are the most successful procedures

TMJ AnkylosisTrue bony ankylosis of the TMJ involves fusion of the head of the condyle to the temporal bone.

Trauma to the chin of is the most common cause of TMJ ankylosis although infection also may be involved

Children are more prone to ankylosis.. Why ??

Limited mandibular movementDeviation of the mandible to the affected sideFacial asymmetry may be observed in TMJ ankylosisOsseous deposition may be seen on radiographs

Important causes of intracapsular ankylosis

TraumaIntracapsular comminuted fracture of the condyle disorganizes the joint. Forceps delivery at birth

InfectionOtitis mediaOsteomyelitis

Systemic juvenile arthritisPsoriatic arthropathyOsteoarthitisRheumatoid arthritis

Neoplasms Chondroma , osteochondroma , osteoma

Management

The various surgical modalities include interpositional arthroplasty, arthroplasty with costochondral graft (CCG), gap arthroplasty , and recently arthroplasty and condylar reconstruction by distraction osteogenesis.

In interpositional arthroplasty, different alloplastic materials and autogenous tissues are in use. Different alloplastic materials are: Metallic prosthesis such as moulded vitallium prosthesis which covers glenoid fossa, Proplast Teflon implant, Silastics, Acrylic spacer and Total joint prosthesis .

GAP ARTHROPLASTY

TMJ fracture

Fractures of the condylar head and neck often result from a blow to the chin

The patient with a condylar fracture usually presents with pain and edema over the joint area and limitation and deviation of the mandible to the injured side on opening.

Intra capsular nondisplaced fractures of the condylar head are usually not treated surgically.

Early mobilization of the mandible is emphasized to prevent bony or fibrous ankylosis

Bilateral condylar fracture may result in anterior open bite

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