There are many different types of TMJ, and each type may be a result of multiple causes.
- Cervical Acceleration/Deceleration (Whiplash)
- Air Bag Deployment
- Opening Too Wide
- Ligament Laxity
- Systemic Diseases
According to statistics published in the Journal of the American Dental Association in 1990,* 44% to 99% of TMJ problems are caused by trauma. By trauma, we mean an injury as obvious as a blow to the jaw with a fist or something as subtle as a whiplash injury with direct trauma to the head or jaw. (*JADA 1990;120:267)
When a person is riding in a vehicle and is struck by another vehicle, often soft tissue injuries in the neck, back, and TMJs may occur. Although the injury may occur from any direction, usually it comes from the rear.
When a Cervical Acceleration/Deceleration (CAD) or Whiplash injury is produced, the head is thrust in the direction of the impact. For example, when a car sitting at a traffic light is struck from the rear by another car, the heads of the occupants in the first vehicle are thrust backwards towards the rear. As the head is thrown backwards, inertia (remember Newton’s Law that a body at rest tends to stay at rest until acted upon by an outside force?) causes the lower jaw or mandible to remain where it was in space for about 250 milliseconds (about 1/4 of a second). This violent motion, causing the head to be thrown backwards, also causes anterior mandibular displacement as the mouth is forced open. Note that opposite to what it might seem, initially during a rearend whiplash injury, the rearward or posterior thrust of the head causes anterior instead of posterior TMJ injury. This produces stretching and/or tearing of the ligaments and connective tissues in one or both TMJs, bleeding, and often displacement of the articular disc in the TMJ.
At the moment of impact from the rear, as the head is thrust backwards, the vehicle is actually accelerated forward as the body of the occupant moves backward, thus forcing him or her into the seat. As the mouth is thrown open, producing TMJ injury, the head either hits the head rest or extends over the headrest.
Then, as the vehicle comes to rest, the occupant continues moving forward until he or she is stopped either by a lap belt and shoulder harness, or the steering wheel or windshield. During this last movement, the head is thrust forward while inertia causes the mandible to be thrust suddenly backward, traumatically closing the mouth violently. This motion may fracture or chip teeth and further injure the posterior part of the TMJ. Note that with the development of all the above injuries, no direct trauma to the head or jaw has yet occurred, demonstrating that direct trauma IS NOT NECESSARY for a whiplash injury to severely damage the TMJs and teeth.
Common complaints following a CAD or Whiplash injury may include:
- Neck pain
- Neck stiffness (difficulty in turning the head)
- Headaches (especially temporal and occipital –where the neck attaches to the head)
- TMJ symptoms (joint pain, limited opening of the mouth, change in bite, TMJ noises, pain in face and TMJs with opening of the mouth, ear pain)
- Visual changes (light sensitivity, blurred vision, etc.)
- Swallowing difficulties and even hoarseness
- Air Bag Deployment
Direct trauma to the mandible in auto accidents, like indirect trauma in whiplash injuries, are both known to produce TMJ injuries. Recently, however, the advent of air bags, which no doubt have saved numerous lives, has been implicated in causing TMJ problems.
Patients who’ve been injured with air bags often have the following symptoms:
- Burned or abraded skin on the chin, face, and even the nose
- Almost immediate TMJ pain
- Swelling of the TMJs
- Limited mouth opening
- Lateral and cervical neck pain
- Change in the dental occlusion (bite)
All joints have limitations to movement and the TMJ is no exception. If you open wide for a long time, or if your mouth is forced wide open, ligaments again may be torn. Swelling and bruising develop and disc dislocation may occur. For example, if your mouth is open for a long time at the dental office while having a tooth prepared for a crown, the joint can dislocate. This rarely happens without a prior history of trauma; however, it does happen. Also, this type of injury may occur if someone’s mouth is opened too wide when they are being put to sleep for surgery. Again, both of these examples are accidental consequences of the given procedures.
Bruxism is the abnormal grinding of the teeth. If grinding continues, TMJ may develop. Bruxism usually occurs during sleep. That is why so many people do not realize that they are bruxers. One indication that a person is a bruxer is sore jaw muscles when waking in the morning. Some researchers feel that the constant grinding of the teeth causing pressure on the TMJs may injure the ligaments, thus allowing for the disc to dislocate. At the very least, bruxism produces muscle pain, and sensitive and worn teeth.
Malocclusion is simply a bad bite. Malocclusion may be produced by poor development of the jaws or removal of teeth without replacement, a high dental restoration, a poor fitting denture or partial denture, or a displaced TMJ disc.
Some dentists feel that orthodontic treatment, or braces, might be a cause of TMJ. By moving teeth with orthodontic appliances, malocclusion is produced during treatment. Also, people undergoing orthodontics do report sensitive teeth, pain in the jaw muscles, and even bruxism. However, as with malocclusion, there has been no scientific controlled study to prove that orthodontic treatment produces a TMJ problem.
People who appear to be double-jointed actually suffer from a problem termed aligament laxity. If this occurs, then the joint appears to be double or loose. This definitely can happen to the TMJs. Ligament laxity is a fairly common problem in active young women who suffer from TMJ (and injuries to other joints).
Stress has many effects on our bodies: some good and some bad. Stress can be both physical and psychological. Physiological changes can produce muscle tightness and pain, and if you are subjected to chronic stress, these physical changes may produce harmful effects. For example, people subjected to chronic stress develop ulcers, diarrhea, tension headaches, muscle tightness, and other physical symptoms. Stress is just like throwing gasoline on an existing fire: the fire is a TMJ problem and the gasoline is stress. The gasoline causes the fire to flair up and burn vigorously for a time, but the gas did not produce the fire (or TMJ), it just made it worse. This is how stress appears to act in conjunction with a TMJ problem. Muscles tighten, teeth clench, abnormal pressure is forced against the TMJ disc, and if the ligaments are weak or if the patient has ligament laxity, then the disc may dislocate.
Various diseases can cause or aggravate TMJ problems. Immune disorders such as rheumatoid arthritis, psoriatic arthritis, and systemic lupus erythematosus can produce inflammation in the TMJ. In addition, viral infections such as mononucleosis, mumps, and measles can cause damage to the surfaces of the TMJ, which ultimately can lead to an internal derangement.