The Temporomandibular Joint

The temporomandibular joint is a typical joint with two bony surfaces – the temporal bone and mandibular, or lower jaw bone. It also has a cartilaginous disc between the two bones. Just like other joints, the disc, ligaments, joint capsule, or muscle can be injured or be a source of pain. Individuals with TM joint issues may suffer from headaches, pain with eating, popping or clicking in the jaw joints, limited ability to open the mouth, sleep issues, fatigue, and GERD. In addition, there may be a history of grinding the teeth that can cause damage to the teeth.

Recent research suggests that TM joint issues result from sleep-disordered breathing due to inadequate airflow. An individual with TM joint issues generally has a small jaw, leaving little room for the tongue. The tongue may fall back, limiting airflow when sleeping. When oxygen is reduced to the brain, the child wakes and then returns to sleep, but frequent waking can lead to fatigue and possibly ADHD. Teeth grinding at night is due to the body’s attempt to keep the airway open. The child is not benefiting from restorative sleep. During the day, posturing with a forward head opens the airway.

Contributing factors may include tongue-tie, orthodontal work with removing teeth, use of pacifiers or thumb-sucking, and a history of a stuffy nose resulting in the habit of breathing through the mouth. When these factors are present, the tongue becomes weak and does not press up against the palate, contributing to a narrow high dome palate instead of a flatter palate that further limits nasal breathing. In addition, the American diet of processed foods does not challenge the jaw muscles to promote bone growth of the palate.

Rest Position of the Jaw
This is the normal resting position of the jaw: teeth are apart, the tongue is fully on the roof of the mouth, and lips are together. Your teeth should never touch. Even when you eat, there is food between your teeth.

The resting position of the jaw is affected by your posture. When you slouch and look straight ahead, your lower jaw elevates as though clenching. If you gently tap your teeth together, you will notice that your bite differs from when you sit up straight.

Posture
Individuals with TM joint pain have a forward head posture that contributes to a change in how the joint moves. When the head is forward, the mandible (or lower jaw) stays back due to the pull of the soft tissues. This causes a change in the alignment of the jaw joint. The mandibular head stays back even though the head is forward. This changes how the joint moves, as the mandibular head is no longer in the center of the joint. When the mandibular head glides forward, it can pull on the disc, which then causes clicking or popping in the joint as it moves over the disc. Over time, the disc can be stretched and deformed to the point that it is pushed fully forward and limits opening.

To understand how the jaw moves, first learn the correct sitting posture:

• Sit in a chair with your feet on the floor.

• Rock your pelvis back and forth until you feel your “sit bones.” When you feel your “sit bones” stop, as now your lumbar spine (lower back) is in neutral alignment.

• You will feel your chest rise.

• Allow your head to glide back, making a double chin so that your ears align with your shoulders and/or your chin is over your breast bone.

To understand how the jaw joints are affected by posture, do the following:

• Posture correctly as described above.

• Place your hands over your jaw joints in front of your ears.

• Open and close your mouth. Initially, you should not feel outward motion, but as your mouth opens further, you will feel the mandibular heads glide outward into your fingers.

• If you slouch, you will feel the mandibular heads move into your fingers immediately, as the initial jaw rotation is lost due to the forward head positioning. If you naturally posture with your head forward, you will feel the mandibular head move into your fingers immediately.

Exercises for the TM Joints
Normal movement of the TM joints can be restored by changing the forward head positioning, providing that the disc has not been fully displaced. Specific exercises can be performed to reinforce correct movement strategies of the joints.

• Sit up straight as described above. Place your index and 3rd finger over the TM joint just before the ear. Place the tip of your tongue on the spot just behind your two front teeth. Press your mid-tongue to your palate. Maintain the tongue position as you slowly open your mouth. You should not feel the TM joints move into your fingers. If you do, make sure the head is in the correct alignment and that the tongue is pressed to the palate. Perform the exercise six times, six times per day.

• Sit up straight as described above. Place your tongue on your palate, with the tip behind your two front teeth. Gently press the side of the chin with your index finger. Next, gently press the other side. Gently press downward with your finger below the lower lip. Gently press upward with your finger on the underside of the chin. Perform six times, six times per day. This exercise helps the brain connect with the TM joint, much like balance exercises. Press lightly. It is not a strengthening exercise.

• To further strengthen the tongue, cluck the tongue. Perform tongue presses upward to the palate. Be sure to press the back of the tongue upward against the palate. The end goal is for the entire tongue to rest on the palate.

Tongue Exercises
If your child has a tongue tie, myofunctional therapy is recommended for five weeks before having the tie surgically released. If the tongue is not strong enough, the surgical procedure will not be successful, as the incision may scar down, and the tongue cannot maintain mobility.

Myofunctional therapy is also utilized to strengthen the tongue if it is weak post-use of pacifiers and thumb-sucking. Myofunctional therapy is provided by dental assistants who have gone through certification. Physical therapists who work with this population may also provide tongue and postural exercises.

Epigenetics, Dental Appliances, and Splints
Please refer to the March 18, 2024, CHYP blog by Sylvia Orozco Silberman, DO MS, entitled “A Simple Introduction to Epigenetics: Updating Our Perspective on How Our Genes Influence Our Health” for further information. Epigenetics is the study of how your behaviors and environment can cause changes that affect how your genes work. Regarding the TM joint, using pacifiers, thumb-sucking, tongue-tie, and eating a soft diet alter bone growth of the upper and lower jaw. This results in a jaw that is too small for the tongue, leading to airway restrictions and subsequent TM joint pain.

Fortunately, there are dental appliances that can reverse these changes, allowing your child to reach their epigenetic potential. Some appliances are removable, and others are permanent for the duration of the treatment. There are surgical options, but these options cause changes via surgery instead of encouraging the epigenetic potential. Dental appliances can facilitate lateral and anterior growth of the palate. The lower jaw grows to fit the upper jaw.

If your child has TM joint pain, a splint can be made to protect the teeth from grinding and reduce the pain. In addition, the splint is designed to bring the lower jaw forward, allowing the joint to be centered correctly, which reduces compression and damage to the disc. Splints are designed to reduce pain at the TM joints and to protect the teeth but do not expand the palate and lower jaw.

During treatment with a dental appliance, your child may benefit from physical therapy, craniosacral therapy, and myofunctional therapy with the goals of improving posture, improving tongue mobility and strength to allow the tongue to rest on the palate, and reducing current symptoms. Physical therapy can also address jaw clicking with exercises and posture education.

Sleep
Since TM joint issues are caused by the body’s attempt to breathe, especially when sleeping, observe your child when he or she is sleeping. Does your child snore or breathe through the mouth? Mouth breathing may also occur if the nose is stuffy. Because the palate may be narrow from the consistently low position of the tongue, this can also contribute to the ability to breathe.

A deviated septum in the nose can contribute to breathing difficulty. If you press your finger into the side of the nose, blocking one nostril, is the airway clear or limited? Compare to the other side. If limited more on one side, this may be due to a deviated septum or a small nostril from a narrow upper jaw.

There are interventions to address chronic stuffy nose and mouth breathing, but they should be done under the advisement of a health professional. To be evaluated for impaired mouth syndrome, an Airway-centered Mouth Doctor (AMD) is recommended.

It is important to breathe through the nose because when you do, nitric oxide is released into the brain. Nitrate Oxide is a strong signaling molecule that plays an important part in endothelial function (endothelial cells line the blood vessels and regulate the exchange between the bloodstream and surrounding tissues). It affects metabolic and vascular health, as well as the health of the nervous system and immune systems, and is also important in contributing to restorative sleep.

References
Your Child’s Best Face: How to Nurture Top Health & Natural Glow, Dr. Felix Liao

License to Thrive, Dr. Felix Liao

Rouse DDS Jeffrey S., “The Bruxism Triad, Sleep bruxism, Sleep disturbance, and Sleep-related GERD,” Inside Dentistry, May 2020: 32-44