What is “TMJ”?

The term, "TMJ", has been commonly used in magazine articles and in television reports and elsewhere as if it designates a distinct, well-defined disorder. This misrepresentation, although innocent, has led to a certain amount of confusion among the general public. This term, "TMJ", actually refers to a broad class of musculoskeletal conditions involving the Temporo – Mandibular – Joint, or jaw system. (read more...)

The American Dental Association has sanctioned "TMD" (Temporo-Mandibular Disorders) as the proper terminology. This is a better term for general use, although it, too, refers to the same broad class of disorders, not to a specific condition. Both of the terms, TMJ and TMD continue to be used in the scientific literature. The American Academy of Orofacial Pain has defined TMD as: "Temporomandibular joint disorders (TMD) characteristically have symptoms of pain and dysfunction of the muscles and joints of the jaw system. The pain may refer to the teeth, sinuses or ears, making it difficult for the patient to tell the origin of the pain."
The symptoms most commonly associated with temporomandibular disorders include:

      • Stiffness, tiredness, and/or pain in the jaw
      • Chronic, recurring headaches, particularly in the temples or behind the eyes
      • Clicking, popping or grating sounds in the jaw joints
      • "Earaches", which may actually be pain in the jaw joints
      • Pain in the jaw when chewing or opening wide
      • Restricted jaw opening, catching or locking of the jaw
      • Difficulty, discomfort or pain when closing the teeth together in a "normal" bite
      • A bite that feels uneven or "off" in some way

Patients presenting for treatment of TMD often report several of these symptoms but when the condition is first developing, any single symptom may be of significance in early diagnosis and treatment.

A Healthy Jaw System

With respect to the jaw system, most people think of their teeth and gums as the primary structures that need to be maintained in a state of health. People who receive regular dental care and who practice good oral hygiene reasonably assume that their chewing mechanism is being maintained in a healthy state. However, there can be ongoing changes in the TMJ and the muscles that control movement, jaw function, and occlusal contact position. These parameters are not usually a part of a routine dental examination, and therefore changes involving altered function in the joints and muscles often go undetected. There is no other joint system in the human body that involves such a complex interplay of musculoskeletal components as occurs during jaw function . (read more...)

In a healthy jaw system, the temporomandibular joints are structurally intact and function without pain. In addition, the dentition is intact and supports and protects the joints. The TMJs direct the path of closure as the teeth come together and provide the guidance during jaw movement. This means that for optimum function, the fit of the bite must be harmonious with the structure and function of the jaw joints. This promotes pain-free, efficient movements during normal jaw activity. When either the TMJs or the dental occlusion are compromised, the muscles must compensate, thus altering jaw function.

Problems in the Jaw System

To appreciate the problems that can progressively develop in this system, it is important to understand the role of each of the individual components of the system.

The Temporomandibular Joints
These highly complex joints are structurally and functionally unique in the human body. (Read more by selecting TMJ Anatomy in the menu at the left) The interposed disc functions as a shock absorber and provides a congruous surface between the incongruous shapes of the condyle and articular tubercle. The complex hinge and sliding movements of the compound TMJ are facilitated by the independent rotation and translation (sliding) of the disc over the condylar head. This shifting position of the disc, with its variable thickness, maintains contact between the articular components during chewing. (read more...)

Reports of a history of clicking, popping or crepitus sounds range from 24% to 49% of the general populations, and in all studies females showed a higher prevalence of joint sounds. Joint sounds usually indicate a structural change, yet despite this alteration, most individuals do not experience any significant pain or other difficulty. Episodes of locking are reported by 7% of male and 13% of females surveyed, but only 4% of males and 7% of females reported impaired function associated with the jaw dysfunction. Although unpredictable, for some these early structural changes may predispose the person to developing jaw pain and dysfunction later in life.

TMJ clicking or popping, without pain or catching of the joints, may not be of concern. However, this situation should be monitored and at the first sign of progression to louder popping, catching or locking, or onset of pain merits a more thorough examination and probably treatment. If evaluation is delayed, the problem may progress and may become more difficult to treat. Go to TMJ Anatomy

The Role of the Teeth
Today, with proper oral hygiene and regular dental maintenance, most people can keep their natural teeth for a lifetime. The loss of even a few teeth can represent a major compromise to the function of a healthy jaw system through loss of some of the support that the teeth provide for the TMJs. The support of a solid bite is critical to the healthy function of the joints and muscles.

You will always close where the teeth fit together best, whether or not it is a good position for the jaw joint or for the muscles that control the jaw. Many people think of a “bad bite” as primarily an esthetic problem. However, even though the teeth may look great and may superficially appear to fit well, a bite discrepancy can still exist and can contribute significantly to problems with the temporomandibular joints and/or the muscles that control the function of the jaw.

Very few people have a truly ideal bite and fortunately the body is often able to adapt and accommodate. However, even though adaptation to these discrepancies may have occurred over many years, if sufficient stresses develop within the jaw system the body’s ability to adapt may be exceeded and pain and other problems of abnormal function may be the eventual result.

The Muscles of Mastication
When problems within the jaw system begin to surface, they are most commonly seen first in stiff, tight muscles and perhaps in difficulty opening or difficulty being able to hold the mouth open, such as at dental appointments. This condition may gradually lead to painful jaw muscles that can appear as headaches or a tired or aching feeling in the jaw. Most muscle pain is a result of overuse of the muscles for any of several reasons.

Usually the body is able to adapt and accommodate, to some degree, to a bad bite. When this occurs, it is the muscles that initially do most of the accommodating. Most people are unaware of a high spot in their bite or other discrepancy. The reason for this is that the muscles will adjust the jaw, if they can, to avoid the high spot. This is a little like taking a hike with a rock in your shoe. With each step, certain muscles, which are not normally used in walking, are now repeatedly used to “compensate”, to avoid stepping on the rock over and over. After a while, the result can be sore muscles in the leg or hip. A very similar thing occurs when the jaw muscles need to “compensate” for a bad bite. With time, and perhaps with the addition of other sources of strain in the muscles, jaw muscle pain will develop from the muscles that are functioning in a “compensated” manner.

When pain develops in the TMJs, the jaw muscles will tighten to protect the painful joints. This chronic, prolonged tightening, referred to as “protective muscle splinting”, with time can also contribute to pain in the muscles. Clenching and grinding the teeth also contributes to excessive use of the muscles.

Any of these factors, as well as stress and certain systemic condition, can adversely affect jaw muscles, leading to muscle fatigue, muscle incoordination, and pain. Often a combination of these factors occur at the same time, causing muscle pain or headaches.

The first objective of treatment of a jaw problem is, of course, to control or eliminate the pain. But it is equally important to provide an environment in which all of the affected components of the system can achieve homeostasis, a return of normal function, or as near to that as is possible. Restoring this level of homeostasis is the best means of minimizing the potential for these problems to recur chronically in the future.