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The temporomandibular joint is the joint of the jaw and is frequently referred to as TMJ. There are two TMJs, one on either side, working in unison. The name is derived from the two bones which form the joint: the upper temporal bone which is part of the skull, and the lower jaw bone called the mandible.
The unique feature of the TMJs is the articular disk. The disc is composed of fibrocartilagenous tissue (this allows the joint to remodel, unlike other joints in the body that are covered in hyaline cartilage).
The TMJs have an articular disk that divides each joint into two. The lower joint compartment formed by the mandible and the articular disc is involved in rotational movement (opening and closing movements).
The upper joint compartment formed by the articular disk and the temporal bone is involved in translational movements (sliding the lower jaw forward or side to side).
The part of the mandible that mates to the under-surface of the disc is the condyle. The part of the temporal bone that mates to the upper surface of the disk is the glenoid (or mandibular) fossa.
Pain or dysfunction of the temporomandibular joint is commonly referred to as "TMJ." In fact, TMJ is really the name of the joint. Temporomandibular disorder is abbreviated TMD. This term is used to refer to a group of problems involving the TMJs and the muscles, tendons, ligaments, blood vessels, and other tissues associated with them. Some practitioners might include the neck, the back and even the whole body in describing problems with the TMJs.
The animation below shows both how a healthy temporomandibular joint should work and how it fails to work properly when a person has temporomandibular joint disorder.
TMJD can be complex to treat. TMJD can affect the joint that connects the lower jaw to the skull, muscles, ligaments, tendons and the teeth. Different approaches to treating TMJD are used depending on the cause of the condition. These approaches are described below.
Arthrocentesis for TMJD
This procedure involves inserting a needle into the temporomandibular joint so that fluid can be flooded through the joint to remove debris and byproducts from inflammation.
The procedure is done under local anesthesia on an outpatient basis. Two needles are inserted into the joint space. One is used to inject saline (salt water) into the joint. The other is used to draw fluid, debris and inflammatory byproducts out of the joint.
After the procedure, the patient is given pain relievers for discomfort from the needles. The patient must wear an oral splint at night to reduce the load on the temporomandibular joint. For about a month after the procedure, patients must do exercises to stretch the jaw muscles.
Arthrocentesis can be effective for patients who are not able to open their mouths fully. This means that the patient is not able to open his or her mouth more than 25 to 30 millimeters without having pain. The pain may be severe even when the jaw isn't being moved.
Corrective or Reconstructive Dentistry or Orthodontics
In some cases, TMJD can be helped by corrective dental treatment. This may involve balancing the biting surfaces of the teeth, replacing missing teeth or replacing fillings or crowns that have been damaged or become eroded. Orthodontics is a process that repositions teeth to improve the bite and alignment of the jaws. A dentist may also be able to fit a patient for mouth guards or splints to help prevent grinding of the teeth at night or to improve the position of the jaw.
Medications For Pain Relief
In some cases, over-the-counter pain relievers such as aspirin or acetaminophen may be helpful. However, if the pain is due to nerve issues, these may not be effective in managing the pain of TMJD. Certain anti-depressants may be helpful in relieving pain. Tricyclic antidepressants such as amitriptyline or nortriptyline taken at bedtime sometimes help relieve TMJD pain. If there is significant pain and joint inflammation, corticosteroid drugs may be injected into the joint space to provide relief. In some cases, injecting botulism toxin (such as Botox) into the jaw muscles used for chewing relieves some types of pain associated with TMJD.