What is Temporomandibular Joint?

TMJ is an abbreviation for the anatomic structure known as the temporomandibular joint. The TMJ is the jaw joint that is located in front of the ear. This is where the lower jaw (mandible) hinges at the base of the skull to allow the mandible to open and function.

TMJ Anatomy by MRI

In the TMJ the mandibular condyle fits into a socket (glenoid fossa) at the base of the skull. During initial opening of the jaw, the condyle rotates in the fossa. During wide opening of the jaw, the condyle slides forward out of the fossa. In between the condyle and the glenoid fossa is a thick fibrous disc that acts like a cushion between the condyle and the fossa. The TMJ disc normally rides in unison with the condyle as it rotates and slides. 

The disc is attached to the superior head of the lateral pterygoid muscle in front. Part of the superior head of the lateral pterygoid and the inferior head of the lateral pterygoid attach to the mandibular condyle in front. These muscle attachments assist in wide opening of the jaw as they pull the disc and the mandibular condyle forward. In back, the disc is attached to loose connective tissue that contains nerves and blood vessels. The entire TMJ is surrounded by a fibrous capsule.

Too often the term "TMJ" is used as a diagnostic term. Many people with pain in the area of the TMJ are told that they have "TMJ". That is like telling someone with abdominal pain that they have "appendix".

There are a variety of possible causes for pain in the region of the TMJ. The following is a list of possible causes of pain in the region of the TMJ:

Possible Causes of Pain in the TMJ Region

Muscle splinting/spasm (myofascial dysfunction)
Headache (migraine, cluster, etc...)
Trauma to the lower jaw (fracture, disruption)
TMJ disc dislocation
Arthritic changes of the mandibular condyle

Muscle inflammation (myositis)
Trigeminal neuralgia
Unbalanced bite (malocclusion)
Inflammation of the TMJ (capsulitis)
Tumor in the TMJ region

Only a thorough physical examination and diagnostic testing, if necessary, will reveal whether or not there is a problem with the actual TMJ itself.

How do I know if I have a TMJ problem?

TMJ disorders are characterized by functional limitations of the lower jaw. Typically patients complain of not being able to open normally or report pain with opening, speaking, or chewing. Patients may experience locking of the jaw in the open or closed position and may frequently experience clicks, pops, or grinding in the TMJ region.

Pain, alone, without functional limitations is not diagnostic of a TMJ problem. The cause or etiology for pain in the head and neck region is sometimes hard to find. Too often, when the cause of pain in the TMJ region is not readily apparent, patients are told that they have "TMJ" by default.

If you are experiencing pain in the TMJ region,  only a thorough physical exam and diagnostic testing, if necessary, will determine the cause. 

Who should I see if I think I have a TMJ problem?

Most patients will initially see their general dentist about a TMJ problem. Typically the dentist will then refer the patient to an oral and maxillofacial surgeon for further evaluation and recommendations for treatment. Some general dentists are experienced with TMJ disorders and may choose to diagnose the TMJ disorder and to initiate treatment themselves.

Dental specialists such as prosthodontists and orthodontists may also provide diagnosis of TMJ disorders and be involved in treatment. Medical specialists such as Ear, Nose and Throat (ENT) doctors may do the same.

Ultimately, however, if a patient needs surgical management of a TMJ disorder, an oral and maxillofacial surgeon will be involved.

How are TMJ problems diagnosed?

A proper TMJ evaluation starts with a thorough head and neck examination. A thorough medical history is also important. This includes any history of trauma to the jaw or history of previous TMJ problems and habits such as clenching and grinding the teeth.

If a TMJ problem is diagnosed, your doctor may order further tests to confirm the diagnosis and to determine the severity of the problem. The following table illustrates the tests used:

Diagnostic TMJ Test
Arthrogram

How the Test is Performed
X-ray sensitive dye is injected into the TMJ joint capsule and x-rays of the TMJ are taken.

Information Gained
Superior test for determining disc dislocation and disc degeneration or perforation. Sometimes in cases of mild disc dislocations this test may be therapeutic in itself as the fluid dye allows the disc to "float" back into place.

Diagnostic TMJ Test
Panorex X-ray

How the Test is Performed
A panorex machine takes a two dimensional x-ray of the TMJ.

Information Gained
Can determine bony changes of the condyle and  fractures or severe dislocations of the condyle. Does not image soft tissue, so the position of the disc cannot be determined by this test.

Diagnostic TMJ Test
Tomograms

How the Test is Performed
A specially designed x-ray machine produces images that represent a "slice" through the TMJ.

Information Gained
Can determine bony changes of the condyle. Shows the relationship of the condyle to the fossa in an open and closed position. Does not image soft tissue, so the position of the disc cannot be determined by this test.

Diagnostic TMJ Test
Magnetic Resonance Imaging

How the Test is Performed
Also known as an MRI. A non-invasive imaging technique for examining soft tissue structures.

Information Gained
Images the soft tissues of the joint. Used to verify dislocations of the disc. Perforations of the disc can sometimes be seen on an MRI.

How do you treat a TMJ problem?

Treatment of TMJ disorders depends upon the nature and severity of the TMJ problem. The following table illustrates the various ways TMJ problems are treated and the indications for those specific types of treatment.

Treatment
Physical therapy*

Description
Treatment by a physical therapist using  several modalities of treatment including stretching, heat, and muscle therapy.

Indications
Useful for muscular disorders that limit the range of motion of the jaw. Patients with severe TMJ conditions that require surgery often have secondary muscle splinting and spasm. Therefore, physical therapy is very useful in the pre and post-surgical period.

Treatment
Splint therapy*

Description
A hard acrylic splint is used to balance the bite (occlusion) or to reposition the lower jaw in relation to the upper jaw.

Indications
Useful for people who grind or clench their jaws. Splints may break up the habit of clenching and grinding. Repositioning splints may help "recapture" the disc if the disruption in the joint is relatively mild.

Treatment
Arthrocentesis

Description
A needle is inserted into the space above the disc (superior joint space) and fluid is injected into the space. An additional needle is then placed into the superior joint space and fluid is run through the joint.

Indications
A conservative surgical procedure that is useful  for acute disc dislocations of the TMJ. Inflating the joint with fluid helps to break up any inflammatory adhesions in the joint and allows the disc to float back into proper position. Not useful in severe inflammatory conditions of the joint or chronic disc dislocation with or without disc degeneration or perforation.

Treatment
Open arthrotomy with disc repositioning

Description
The TMJ is opened up surgically through an incision made in front of the ear. The disc is then brought back and tacked down into proper position.

Indications
Indicated for disc dislocations with resultant dysfunction or severe pain. This treatment may be necessary for disc dislocations when conservative methods have failed.

Treatment
Open surgery with meniscectomy

Description
The TMJ is opened and the disc is removed.

Indications
This is necessary when the disc is severely deformed or perforated and beyond repair. If the joint architecture is otherwise normal, the disc does not need to be replaced. Scar tissue will form in the joint which will serve as a cushion between the condyle and the fossa.

Treatment
Open surgery with silastic implant

Description
When disc needs be removed, a silicone sheet is inserted into the joint space. A capsule forms around the silicone sheet. The silicone sheet is then removed in approximately 4 weeks through a small incision with local anesthesia. A capsule will have formed. 

Indications
This is indicated when there has been some degeneration of the condyle or the fossa. A capsule forms around the silicone implant which is left behind after the implant is removed. This capsule serves as a cushion between the condyle and the fossa.

Treatment
Open surgery with dermal graft

Description
When the disc needs to be removed, it can be replaced with a dermis graft. Dermis is the layer just underneath the skin. The graft is usually taken from the abdominal wall below the waistline.

Indications
This is indicated when there has been some degeneration of the condyle or the fossa. The dermis graft acts as a cushion between the condyle and the fossa.

Treatment
Arthroscopy*

Description
Similar to arthroscopy of the knee, a scope can be inserted into the TMJ in order to visualize the joint internally and to perform limited repairs.

Indications
Arthroscopy is indicated for acute and chronic disc dislocations and inflammatory capsulitis. Relocating the disc using an arthroscope is challenging and treatment success depends on the operator's skill with an arthroscope. Most useful for visualizing the TMJ internally without opening the joint surgically and for treating inflammatory capsulitis.

* services not provided by our office

What are the potential complications of TMJ surgery?

The nature and degree of complications related to TMJ surgery depend on the patient's anatomy, the degree of degeneration within the joint, and the surgical procedure itself. Patients who have had previous TMJ surgery are at higher risk for complications if additional TMJ surgery is performed on the same joint.

As with any surgical procedure, swelling, discomfort, bruising, infection and bleeding may occur. Numbness, which is usually temporary, may occur around the incision site . 

Because of the close relationship between the frontal branch of the facial nerve and the TMJ, paralysis of the upper half of the face may occur on the side where the surgery was performed. This leads to the inability to raise the brow and to close the eye tightly. While this is usually temporary, in some instances problems with the frontal nerve have been known to be permanent.

As with all surgical procedures, the benefits of surgery must be weighed against the risks of surgery. This can only be determined after a thorough examination and discussion with your doctor.