Put your index finger on the side of your face, just in front of your ear. Open your mouth wide and close it a few times. You can feel your temporomandibular joint in action. Now, with your finger still in place, move your chin side-to-side, then stick it forward and pull it back toward your throat. It’s quite a joint, isn’t it? It connects your jaw with your skull and allows freedom of movement in all three planes. It’s like the shoulder or hip joints in its basic design, ball-and-socket. The temporomandibular joint is unique, though. Unlike the hips and shoulders, both left and right sides always work together, never independently.
TMD, Temporomandibular Disorder, is sometimes referred to as TMJ because of the centrality of this amazing joint to the signs and symptoms. The joint itself and the muscles which surround and animate it are involved in this syndrome.
TMD is on dentists’ radar screens for two reasons. First, dentists are often the first of a person’s health care providers to identify and diagnose TMD. The standard dental examination includes screening for signs and symptoms of TMD. Second, some of the causes of TMD are dental issues, and so sometimes the treatment is dental.
SIGNS AND SYMPTOMS
The most common symptom of TMD is pain. The pain can come with any movement of the jaw or can be felt when the jaw is at rest. It can be mild or intense, constant or passing. An episode can last for seconds, minutes, or hours, with recurrences over months or even years.
Another symptom is called “catching”, or locking. The jaw seems to get stuck, usually in the closed position. It seems difficult or impossible to open without severe pain. The “catch” can pass immediately or it can be prolonged. The issue is mechanical. Inside the temporomandibular joint there’s a disc made of fibrous connective tissues, which fits between the ball and socket and acts as a cushion. The ball-and-socket joints in the hips and shoulders don’t have this feature. When the disc gets moved out of place or becomes misshapen, it impairs the free movement of the joint.
Clicking or popping of the jaw, another symptom of TMD, is sometimes another result of a displaced or deformed disc, as the sound is thought to be made when the joint comes out of position and then pops back in during talking or chewing. Stretched or torn ligaments are another potential cause of these “sound effects”.
Dentists also look for abnormalities in the movement of the jaw. Limited range of motion is one sign associated with TMD, with the patient unable to fully open the jaw. The other characteristic sign is deviation of the jaw bone to one side during the opening movement. The particular type of deviation is related to the underlying issue in the joint itself or the surrounding muscles.
Our upper and lower teeth are meant to fit neatly into one another when we close our jaws. This is called occlusion, and when the pieces of this jigsaw puzzle don’t fit together, malocclusion, something has to give. Teeth can shift, but only very slowly, and not having been to dental school they don’t really know where to move to. No help there. The upper teeth are fixed in the skull. That leaves the jaw, which the versatility of the TM joint provides with 3D freedom of movement. When upper and lower teeth don’t join properly, it’s the jaw that has to adapt. Unfortunately, this just transfers the problem to the TM joint, which is then moving and resting in ways that strain its natural capabilities, potentially resulting in TMD.
Another all-too-common cause of TMD is habitual grinding or clenching of teeth. This behavior is undoubtedly the result of stress in some patients. In others, sleep apnea or other sleep disorders appear to be involved as the action occurs almost always at night. In more than a few people, the search for causes of grinding and clenching loops back to malocclusion. It’s as though an effort is being made to make upper and lower teeth fit together by brute force.
PREVENTION AND TREATMENT: DENTIST’S ROLE
Dentistry plays a key role from early childhood in keeping TMD out of a patient’s life. Regular dental exams, starting when the first tooth erupts or by a child’s first birthday, enable the dentist to monitor the positioning of baby and permanent teeth. Baby teeth are place-holders for permanent teeth, so regular care and good home hygiene practices are essential to keep them healthy until their work is done.
Dental x-rays are not usually made on a routine basis with very young children, as a safety precaution. Where there are indications of a potential issue with hidden decay in erupted teeth, or of missing or malformed unerupted teeth, the dentist can do bitewing or panoramic x-rays to guide prompt intervention or referral to an orthodontist or another specialist. Tooth decay needs to be treated promptly in baby teeth since if neglected it can progress to infection and pain that alters the child’s bite, which is a path to developing TMD. Worse, an infected baby tooth may have to be extracted, which almost inevitably leads to shifting of adjacent teeth and so misguides the permanent tooth erupting in the extracted tooth’s place. Kid’s jaws are still growing and developing, and any bite issues put them at risk of altering the shape of this important bone.
As a person grows through later childhood and adolescence, the dentist continues as his or her primary oral health care provider. Orthodonture, where required, is provided by a specialist, but the dentist’s care combats the most common of oral health issues: tooth decay. A good bite eliminates one of the chief causes of TMD. Decay, along with trauma, accounts for most of the missing teeth in adults. Loss of a tooth is followed by a chain reaction of shifting by neighboring teeth, malocclusion, and, potentially TMD. Early detection and treatment of decay keep things in line. Where advanced decay has set in, with infection, root canal therapy and crowns preserve a patient’s good bite.
Dentists are on the front lines where grinding or clenching threaten a patient’s oral health and increase the risk of TMD. Regular exams pick up the signs even when patients are not self-aware and don’t report any symptoms. Dental interventions include nighttime mouth guards and bite plates to protect teeth, coaching to increase patients’ awareness, and behavioral habits to adopt and to avoid.
Some cases of TMD don’t have good dental solutions. The syndrome is sometimes caused by arthritis in the joint, in patients with no dental or oral issues at all. In others, the roots of TMD are not so much dental or medical as psychological. Dentists are trained to identify cases which require the involvement of orthodontists, medical doctors, or other types of professionals, and to make referrals to these.
It’s incumbent on us as patients to call our dentist’s attention to any symptoms or complaints that his or her professional expertise and experience touch on. As a simple rule, that means anything going on from the neck up. Clinical exams and x-rays are fantastic diagnostic tools but they’re not perfect. Patients should never hesitate to raise questions or report unusual sensations. Better to talk too much than too little. Temporomandibular disorder (TMD) is much better avoided than treated, so let’s stop it before it begins.