Signs and symptoms of temporomandibular joint disorder vary in their presentation and can be very complex. Due to the different anatomic structures involved, it is easy to group the symptoms accordingly into three categories. The anatomic structures affected in TMD are the muscles, the temporomandibular joints, and the teeth.
Muscles
Disorders of the muscles of the temporomandibular joint are the most common complaints by TMD patients. The two major observations concerning the muscles are pain and dysfunction. In TMD, the muscle pain is described as a “deep pain” and does not seem to be simply from overuse and fatigue. Instead, it is believed that this pain is a result by mechanisms from the central nervous system.
In these cases, muscle pain can sometimes be associated with trigger points in muscle tissue. The trigger points are attributed to deep, constant pain and to causing the pain to be referred to other parts of the body. For example, the trapezius muscle refers pain more commonly to the ear, temple, and angle of the jaw, while the occipital belly of the occipitofrontalis muscle refers pain to behind the eye. Trigger points residing in the shoulder muscles can also cause muscle disorders of the temporomandibular joint.
Trigger points are also involved with associated migraines in TMD, even though migraines themselves are not fully an aspect of TMD. When pain of the temporomandibular joint precedes migraines, then treatment of the TMD may reduce the number of migraines, but TMD treatment is not a “cure” for migraines. Other kinds of headaches can be an expression of the pain produced by trigger points.
The dysfunction involved is usually a restriction on mandibular movement upon opening of the mouth. In some cases, it is possible to continue opening the mouth if done slowly, but the pain may stay present or intensify. Additionally, the dysfunction of the muscles may cause the teeth to occlude with each other incorrectly. This condition is called an acute malocclusion and is the result of TMD, not the cause.
Temporomandibular joints
Disorders of the temporomandibular joints are usually the most noted observation upon examination of TMD patient because most signs are readily detected by the clinician, not necessarily the patient. The two major observations concerning the joints are pain and dysfunction. In a healthy joint, the surfaces in contact with one another do not have any receptors to transmit the feeling of pain.
The pain therefore must originate from one of the surrounding soft tissues: the discal ligaments, the capsular ligaments, and the retrodiscal tissue. When receptors from one of these areas are triggered, the pain causes a reflex to limit the mandible’s movement. Furthermore, inflammation of the joints can cause constant pain, even without movement of the jaw.
Due to close proximity of the ear to the temporomandibular joint, TMJ pain can be expressed as ear pain. The pain may be referred in around half of all patients and experienced as otalgia (earache). Conversely, TMD is an important possible cause of secondary otalgia.
Treatment of TMD may then significantly reduce symptoms of otalgia and tinnitus, as well as atypical facial pain. Despite some of these findings, there are some researchers who question whether TMD therapy can reduce symptoms in the ear, and currently a debate is ongoing to settle the controversy.
The dysfunction involved is most often in regards to the relationship between the condyle of the mandible and the disc. The sounds produced by this dysfunction is usually described as a “click” or a “pop” when a single sound is heard. When there are multiple, rough sounds, it is described as “crepitation” or “crepitus”.
Teeth
Disorders of the teeth can also be present in TMD patients. Tooth mobility can be caused by destruction of the supporting bone and by heavy forces being placed on teeth. Movement of the teeth affects how they contact one another when the mouth closes, and the overall relationship between the teeth, muscles, and joints can be altered. The heavy forces on the teeth have been associated with the presence of mandibular tori in TMD patients.
Pulpitis, inflammation of the dental pulp, is another symptom that may result. It is usually caused by heavy forces on the teeth and can cause pain. Lastly, tooth wear is the most common sign associated with a dysfunction of the teeth, but it is not strongly associated with TMD symptoms. Tooth wear can be a result of bruxism or by interfering with the movement of the mandible during function, referred to as the “functional envelope of motion.” Depending on the cause, the treatment for tooth wear differs.
