HOW IS TMJ TMD DIAGNOSED?


When a patient consults with a dentist about a TMJ TMD problem, he/she first obtains a history and performs a special clinical examination that includes: head, neck, muscle examination, evaluation of jaw movements and TMJ joint sounds.


Muscle Examination

Light finger pressure, called palpation, when applied to a muscle should not cause a sensation of tenderness or pain. If palpation does cause pain, tenderness or discomfort, it is an indication of the presence of inflammation, hyperactivity or spasm in a muscle.


Muscles Outside the Mouth (extraoral)

The doctor gently palpates the muscles responsible for the movements of the jaw on the sides of the temples (temporalis) and the sides of the cheeks (masseter). The masseters are pressed between fingers outside and inside the mouth. Both of these muscles close the mouth. The masseter tenses as you clench your teeth together. Below the jaw is a group of muscles, which open the mouth. The most important, the digastric muscles are palpated below the jaw and at the rear corners of the jaw. The angle of the mandible (the back corner) below the ears is palpated. In patients with TMD, this area is often tender as it includes muscles and ligaments intimately associated with mandibular movement.


Muscles Inside the Mouth (intraoral)

Inside the mouth, the doctor palpates two very significant muscles on each side. In the upper rear of the mouth behind and above the last molars are the external or lateral pterygoid muscles. These are very important muscles responsible for lateral (side) movement of the mandible as well as opening of the mouth.  Adjacent to the lateral pterygoid muscles is another muscle, the tensor veli palatini, which open the eustachian tube connecting the middle ear and the rear of the throat called the eustachian tube. The eustachian tube equalizes pressure in the ear with outside air pressure. TMD patients may experience spasm of the lateral pterygoid muscle and also of the adjacent tensor veli palatini, which fails to open the eustachian tube.

People may experience muffling of sounds or ear pain due to the failure of the eustachian tube to open properly and ventilate the middle ear. In the lower rear of the mouth, located on the inner aspect of the lowest corner of the jaw, are the internal or medial pterygoid muscles. The medial pterygoid muscles are part of the system, which closes the mouth.


Dental Examination

The dentist examines the amount of overlapping of the upper front teeth over the lower front teeth. Excessive overlap (deep overbite) is often found in patients with TMD (Figure #1). It is commonly associated with overclosure of the jaw and rear pressure in the TMJ joint adjacent to the ear.

The edges of the front teeth are normally smooth and rounded on the corners. If they are worn flat, sometimes showing a brown stain, it is a sign of an abnormal functional habit, which wears away tooth structure. This is often seen in TMD patients (Figures #2 and #3).


Muscles of the Neck (cervical)

The doctor also palpates the muscles, which support and move the head and neck. This examination includes muscles on the front, sides and rear of the neck and the shoulders. Since TMD can co-exist with cervical (neck) musculoskeletal dysfunction, these muscles are often tender. Since the jaw and neck function together, cerival (neck) musculoskeltal dysfunction commonly coexist with TMD.  Disorders within the muscles and nerves in the neck can cause the sensation of pain referred elsewhere in the body confusing the diagnostic and treatment process.


Posture

The dentist will evaluate your posture.  Abnormal head and neck posture can affect your jaw posture, which can contribute to a TMJ TMD condition.  TMD can also be the cause of abnormal head and neck posture.  A forward head posture or tilted head can result in pressures within the neck vertebrae resulting in nerve pressure and muscle fatigue.  All of these structures are interconnected with the relationship between the jaw and skull, its nerve supply and muscle system and the way the teeth fit together.  Other body postural asymmetry in the shoulders, hips and back can also adversely affect head, neck and jaw posture.


The doctor measures the space between the upper and lower front teeth when the mouth is open to its widest position (normal is 35-50 mm). Abnormalities are indicated by reduced capacity to open, opening with pain in the muscles or TMJ joints, and opening towards one side rather than straight down. The doctor also observes the quality of opening as to whether it is fluid or staggered and strained. The doctor will assess the deliberate movement of the jaw to the left and then to the right, recording the maximum range of movement capability.

The TMJ is palpated on both sides of the face with the mouth open wide and closed. Pain or tenderness over the joint is an indication of an inflammation in the joint capsule or within the joints. The uppermost portion of the jaw (the condyle) normally rotates and moves forward as the mouth is opened wide. You can feel this yourself by placing your fingers on the condyles in front of your ears as you open wide and close. If the condyle cannot move forward and downward along the slope of the joint as you open wide, it indicates that either muscles or something within the joint is obstructing or preventing the forward movement (translation). A click may be felt beneath the doctor's fingers. That too indicates an abnormal state.

The TMJ can also be palpated through the outer ear, by application of gentle finger pressure forward on the front wall of the outer ear canal. The finger is never placed deep into the ear canal. The forward wall of the ear canal is actually the rear wall of the TMJ. In the absence of any ear disease, pain on palpation is an indication of inflammation in the tissues in the rear of the TMJ.

Using a medical stethoscope or a Doppler, the doctor listens to the TMJ as the patient opens, closes and moves the jaw from side to side. Sound in the joints is abnormal. The type of sound, whether a distinct click or a crackling sound is significant as each represents a different state of joint dysfunction. The position in the open/close cycle at which sound is heard is also important. Many people have sounds in their TMJ and no other symptoms and may require no treatment.

Notably all of these clinical examination procedures provide diagnostic impressions to the examining physician or dentist to make an initial diagnosis. The computerized instrumentation, which the dentist uses after this clinical examination, provides hard data, actual precise measurements of these same functions; jaw movement, muscle function, TMJ function and joint sounds. Measurements are made at various stages of treatment.


Diagnosis in the Computer Age

Often, a virtually imperceptible (invisible) misalignment of the jaws with upper and lower teeth meeting in the wrong place can be at the root of TMDs. This misalignment can prevent the jaws from meeting in a position, which maintains muscular relaxation and health as nature intended, requiring the muscles to function in an uncomfortable manner. The misalignment may look like a typical dental malocclusion or may look like a beautiful occlusion of the teeth. By visually observing, feeling and listening alone, doctors cannot totally observe and evaluate the presence of subtle dysfunction. To trace and identify this malocclusion, or "unhealthy bite," and to measure the associated muscle function requires a revolutionary set of computerized instruments developed over the past forty years.


THE COMPUTERIZED MANDIBULAR SCAN (CMS)

Computerized ScanningThe CMS is a tracking device that records, in three dimensions, the delicate functioning movements of the jaw with accuracy in tenths of a millimeter. Recordings are made of the movement of a small magnet temporarily attached to the gum below the lower front teeth. Opening, closing, swallowing and chewing movements can be scrutinized and analyzed. The natural occlusion and the healthy neuromuscular occlusion treatment positions can be located with this computerized instrument. This testing is used at the initiation of treatment and thereafter to evaluate the accuracy of jaw position at the treatment occlusion.


THE ELECTROMYOGRAPH (EMG)

This instrument measures and analyzes the electrical activity in the muscles that move the jaw at rest and during function. In health, muscles rest with low levels of electrical activity and function with high levels of balanced activity. In TMD the reverse is often observed. Illustrative data demonstrate the resting EMG activity before and after TENS (electrical stimulation therapy to relax muscles) as well as the Functioning (clench) EMG activity in the natural bite and in the corrected neuromuscular occlusion used for treatment. EMG is a painless test, which is performed using surface electrodes, like band-aids on the face, forehead, side of the head and beneath the chin.

Graph 1


Graph 2


Graph 3


THE ELECTROSONOGRAPH (ESG)

Recordings of sounds produced within the jaw joint (TMJ) can be made during opening and closing of the mouth more sensitively, precisely and reproducibly than by the traditional technique of listening with a stethoscope. ESG records the frequency and amplitude (power) of the noise produced, as well as the position in the opening/closing at which sound is produced. This enables the dentist to evaluate whether there is damage within the TMJ and suggests its nature for which further study may be necessary. The test is performed by placement of a headpiece similar to that of a head set with vibration sensors (transducers) over the two temporomandibular joints (TMJ).


RADIOGRAPHIC EXAMINATION

The doctor determines what type of imaging is necessary for each patient and at what point in the diagnosis or treatment it is necessary to obtain information from imaging. TMJ imaging includes various types of views such as lateral transcranial, frontal, CT scans, and MRI when medically necessary to aid in the diagnosis and treatment of a patient.


DIAGNOSIS

The actual diagnosis is made by the TMD-trained dentist, who accumulates, analyzes and assimilates all of the information obtained from the patient's history, clinical examination and various diagnostic tests described above. The computerized testing, which provides valuable information, does not make a diagnosis by itself. It is the trained doctor, assessing all the outcomes, who makes the diagnosis and determines the appropriate treatment plan. Actual treatment frequently involves the temporary creation of a new therapeutic biting position. This neuromuscular occlusion position incorporates healthy muscle function and proper interdigitation of the teeth to create a healthy, comfortable bite.


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