Keeping Your Jaw Joints Healthy

February 2010

A very old acquaintance, Dr. Pete Dawson who is an icon in the world of dentistry, has spent more hours lecturing about TMJ in dentistry than anyone I know. Dr. Dawson states “if you don’t believe in God before you learn about the TMJ, you will after you do”. This implies just how complex and magnificent the TMJ really is.

The temporomandibular joint (TMJ) is a small joint located in front of each of your ears where the lower jaw comes up and joins the skull.  It permits the lower jaw (mandible) to move and function.  The TM joint moves each time we chew, talk or even swallow. Similar to the ball and socket joint of the shoulder or hip, the TM joint routinely rotates (like when we chew gum), but it uniquely has the amazing ability to function as a sliding joint.  This is really an incredible property for any joint.  This feature of the lower jaw sliding down and forward, as when getting ready eat a thick sandwich, is called “translation”.  The jaw further moves laterally in an infinite range of combined movements, making it truly the most complex joint in the human body.

The TMJ has a disk between the two bones (of the jaw and skull) that acts as a cushion to provide protection, so the bones don’t rub on each other and cause destructive wear.

Jaw Joint PainThe round upper end of the lower jaw is called the “condyle”.  The condyle functions against a part of the skull bone called the temporal bone in a specific area called the “articular fossa”.  Between the condyle and fossa is a disk made of cartilage that allows the condyle to move easily and prevent the two bones from rubbing and causing damage.

As with all parts of the body, the TM joints are taken for granted until they begin to cause us problems.  TMJ disorders, termed temporo-mandibular dysfunction (TMD), are not uncommon and have a variety of symptoms. Patients may complain of earaches, headaches and limited ability to open their mouth. They may also complain of clicking or grating sounds in the joint and feel pain when opening and closing their mouth. What must be determined, of course, is the cause.

Causes of TMD (TMJ symptoms) include arthritis (i.e. rheumatoid arthritis), which can result from an injury or from grinding the teeth at night.  This may cause parts of the TMJ to fuse, preventing jaw movement altogether.   Another common cause involves displacement or dislocation of the disk that is located between the jawbone and the socket. A displaced disk may produce clicking or popping sounds, limit jaw movement and cause pain when opening and closing the mouth.

Problems with Jaw Pain

The disk can also develop a hole or perforation, which can produce a grating sound with joint movement. There are also conditions such as trauma or rheumatoid arthritis that can cause the parts of the TMJ to fuse, preventing jaw movement altogether.

Stress may trigger pain in the jaw muscles and simulate TMJ problems. Affected patients frequently clench or grind their teeth at night causing painful spasms in the muscles and difficulty in moving the jaw. Patients may also experience a combination of muscle and joint problems. That is why diagnosing TMJ disorders can be complex and may require different diagnostic procedures.

Why do people grind their teeth any way?  That is really unknown.  However, people with uneven teeth that grind create very unusual forces on the TM joints and may create TMJ symptoms.  Having teeth pulled that cause teeth to shift and drift into bad positions, wearing teeth down over time, crooked teeth — all create an imbalance the TMJ must endure and that can inevitably flare up and hurt similar to a bad back.

TMJ corrections are most often diagnosed by your dentist and treated by wearing a hard plastic mouthpiece custom designed to provide relief.  If this non-surgical treatment is unsuccessful or if there is clear joint damage, surgery may be indicated (arthroscopic or direct surgery).

Prevention is always the best medicine.  Keep your teeth healthy.  Replace missing teeth.  Get a “nightguard” (grinding appliance) if you suspect you grind or wake up with sore TM joints in the morning.  Get regular check-ups at your dentist and ask about TMJ problems if you suspect you may be experiencing them.