Common Misconceptions
MANY MISCONCEPTIONS REGARDING TMJ DISORDERS AND BITES are common even among dentists.
1) IF I DON'T TREAT MY TMJ PROBLEM, IT WILL GET WORSE - No. It's just as likely to get better, because TMJ disorders are self-limiting. The symptoms eventually “burn out” even without any treatment, because damaged and dislocated TMJs undergo adaptation characterized by fibrosis of the retrodiskal tissues that eliminates the inflammation and restores functional capacity. Successful adaptation may require anywhere from days to decades, but it almost always occurs by middle age. Older people may experience jaw muscle pain as a subset of postural muscle pain and some difficulty chewing if the TMJs and the bite don't fit each other; but their TMJs are unlikely to become inflammed, unless exposed to acute injury (from which they heal quickly), or nightly strain due to wearing an oral appliance that is excessively tall, tight, or uneven.
2) MY PROBLEM IS DUE TO TOOTH WEAR - Doubtful. The idea that tooth wear causes TMJ disorders is intuitively appealing and was taught in dental schools for decades, even though there was no evidence for it. Teeth are made for wear. In our ancestors, the teeth often wore down right through the crowns, leaving people chewing on the roots; without developing pain or dysfunction. Today, teeth that show evidence of wear are healthier periodontally than teeth that do not show evidence of wear. Tooth wear is only a problem if it will prevent your teeth from lasting as long as you do, or if it occurs so rapidly that it causes the little organ inside each tooth (the pulp) to die and need a root canal.
3) IF YOU HAVE HAD ORTHODONTICS, YOU MUST HAVE A GOOD BITE - Not necessarily. In fact, you may have very straight teeth and a badly strained bite. Braces and invisalign are teeth alignment tools. They can align the upper teeth into a perfect arch shape, and they can align the lower teeth into a slightly smaller perfect arch shape; but they cannot control the mandibular location where the dental arches fit together, the critical feature in most TMJ disorders. Also, orthodontics that leaves the dental arches too steeply locked together may cause the bite to become strained over time during adulthood by inhibiting the differential vectors of growth in upper and lower jawbones.
4) MY PROBLEM IS DUE TO NOCTURNAL BRUXISM (CLENCHING AND GRINDING DURING SLEEP) - Nocturnal bruxism is often part of the symptom generating process, but it cannot be considered the cause of your TMJ disorder, because it is part of normal sleep. It occurs to some extent in everybody as a by-product of brain activity during transitions between sleep stages. It occurs more forcefully and frequently when we are under stress, and it can apply a lot of force to the TMJs and teeth, but it is not found more frequently in TMJ disorder patients. In fact, TMJ disorder patients generally have weaker than normal jaw muscles, and thus they apply less force to the TMJs than average people during nocturnal bruxism.
5) MY ANTERIOR OPEN BITE IS DUE TO A TONGUE THRUST DURING SWALLOWING - No, it's due to a protective tongue resting posture. The presence of a space between the front teeth, called an open bite, was thought for decades to be due to the intermittent pressures of a retained infantile tongue thrust, when the tongue pushes forward during swallowing. Then a study using numerous force sensors in the mouths of people who had this condition found that they did not thrust their tongues during swallowing but maintained a resting posture with the tongue interposed between the teeth to protect the pharyngeal airway despite a bite that forces it backward into the pharyngeal airway. In most of these cases, correcting the bite requires expanding the upper dental arch to make room for the tongue to rest up high in the palate before the open bite can be closed by bringing the front teeth together.
6) MY PROBLEM IS DUE TO TONGUE TIE (TIGHT LINGUAL FRENUM) - Doubtful. A tight lingual frenum (ankyloglossia), also called tongue tie, can be a serious problem in babies when it prevents them from nursing or later in young children when it can make it difficult to pronounce sounds like “r, s, z, t, d, l, j, ch, and th. However, it is rarely a problem in adults. A number of dentists have promoted the idea that tongue tie is the cause of low tongue posture and narrow palates, and they have popularized a minor surgery (lingual frenectomy) to cut the frenum. They believe that tongue should be able to maintain a seal against the hard palate even as the mouth opens wide. They correlate tight lingual frenums to sleep apnea and narrow palates, and they promote the surgery to help treat sleep apnea and "improve the pharyngeal airway". However, there is no science or even common sense to support the idea that "releasing" the tongue tie is helpful in the vast majority of people. In adults who can speak normally and lick their lips but have low tongue posture, the cause of the low tongue posture is the narrow palate, not a tight frenum. Also, an important disadvantage of tongue tie surgery or tongue "release" may be removing one of the features that prevents the tongue from shifting back into the pharynx and producing obstructive sleep apnea.
7) ADOLESCENT CONDYLAR RESORPTION (AKA CHEERLEADER SYNDROME) IS IDIOPATHIC - No, This condition (also known as condylar atrophy, idiopathic condylysis, and progressive condylar resorption) is the result of a facial growth pattern in which the mandible rotates down and back so rapidly that it drives the condyles into the TMJs up and forward forcefully enough to produce bone resorption there. Even before this condition was named, it was recorded by a researcher who studied a set of identical twins, one of whom had severe right side TMJ pain. His records (below) show that the twin with the TMJ pain (dotted line in the left side X-ray) had a mandibular condyle that had rotated upward and forward into the temporal bone as the first molar on that side had shifted down and back.
HEALTHY TMJ DAMAGED RIGHT TMJ
Idiopathic condylar resorption is usually treated surgically because of the severity of the condition; but what it needs is restoration of a healthy facial growth pattern, most immediately reduction of the excessive anterior facial height produced by the downward and backward rotation.
8) JAWBONE GROWTH STOPS AT ADULTHOOD WHEN OTHER BONES STOP GROWING - No. After the second decade of life, when our long bones stop growing, our jawbones slow down about 90% and then continue slowly. One reason our jawbones are programmed to keep growing is to increase the space for airway passage during adulthood as muscles weaken at a rate of about 5% per decade, so that the respiratory muscles will not have to keep increasing their effort as we age. Upper jawbone expansion increases the cross-sectional area of the nasal airway passage, and lower jawbone advancement increases the cross-sectional area of the pharyngeal airway passage. The other reason the jawbones were programmed to keep growing is to maintain face height and a stable bite table, even as the teeth wear down to their root tips, by growing in a manner that continually carries the lower teeth upward and forward toward the upper teeth. Adult facial growth is a big inconvenient truth for orthodontists, because it means the teeth do not always stay straight.
9) TMJ DISORDERS AROSE WHEN HUMANS STARTED EATING GRAINS - No, they arose when we started processing those grains into highly refined foods which require so little chewing that our jaw muscles stopped getting the exercise they need to make them strong enough to maintain a healthy facial growth pattern. As can be easily seen from museum skulls, early humans sometimes wore out their TMJs and dentitions, while we more often fail to wear ours in well enough to achieve harmonious function. A detailed comparison between craniofacial growth in our recent pre-industrial ancestors and modern people can be found in chapters 3 and 4 of ETIOLOGY.
10) THE CAUSE OF TMJ DISORDERS IS MULTI-FACTORIAL - No. That fallacy persisted for years as a result of patients reporting a variety of different types of events that appeared to immediately precede their symptoms, but those events were just triggers. For example, the cause of your TMJ injury was not that time you bent incorrectly or chewed a stale bagel, the cause was an ongoing facial growth strain that required constant adaptation to prevent damage. You cannot successfully treat the condition by being careful to avoid extreme ranges of jaw movement such as opening wide, chewing hard food, or resting your jaw on your hand. The multi-factorial theory is discussed in more detail in CAUSES under the tab FOR DOCTORS.
11) X-RAYS SHOW THAT MY TMJ PROBLEM IS TOO SEVERE FOR NON-SURGICAL TREATMENT. Nonsense. X-rays can show changes that have occurred in the shape of the bones at the TMJs, but they cannot tell when those changes happened or if they have any relevance to your current clinical condition. Most old TMJs have undergone extensive damage and remodeling, which makes them look bad on X-ray, but the remodeling was part of a successful anatomical adaptation that eliminated the symptoms.
12) BOTOX IS A GOOD SOLUTION TO MY PROBLEM - Botox is one way to temporarily reduce the jaw muscle forces used in nocturnal bruxism. In doing so, it can relieve symptoms that are produced by a symptom generating cycle in which nocturnal bruxism is one of the factors in the cycle. However, Botox reduces the jaw muscle forces in bruxism by damaging the jaw muscles, which are responsible for regulating jawbone growth; and unregulated jawbone growth is the root cause of most TMJ disorders; therefore weakening the jaw muscles makes TMJ disorder symptoms likely to return later. Botox is now being marketed as a way to produce "facial slimming". It slims the face by weakening the jaw muscles. A much healthier way to reduce the jaw muscle forces used in nocturnal bruxism is by wearing a front flat bite plate appliance, because it produces the same effect without damaging the muscles; and its effect lasts as long as the appliance is worn. Also, the orthopedic appliance has important growth benefits that Botox lacks.
13) BITE CHANGES FROM MANDIBULAR ADVANCEMENT APPLIANCES SHOULD BE PREVENTED - No, this issue is misunderstood. The bite changes that commonly occur after wearing mandibular advancement appliances to treat sleep apnea cause great confusion among dentists, because treating them requires adjusting bites forward, and dental schools in the past have only taught dentists how to adjust bites backward. As a result, dentists go to great lengths to try and prevent the bite changes that almost always occur in people wearing mandibular advancement devices. However, these bite changes can be managed to our benefit, as described in MULTILEVEL ORAL APPLIANCE TREATMENT OF SLEEP APNEA under the tab FOR DOCTORS.
14) ADJUSTING BITES BY DRILLING ON TEETH (EQUILIBRATION) MAKES THEM SUSCEPTIBLE TO DECAY - Just not true. Many people believe that the enamel on teeth protects the dentin from decay, and therefore that any defect in the enamel increases the susceptibility to decay; but that's not how teeth work in mammals. Evolution combined enamel and dentin to produce tooth structures that wear down in a manner that creates effective grinding surfaces. Cavities only form where food gets stuck or plaque is allowed to accumulate, whether that area is covered by enamel or dentin. The acid produced by the bacteria drills a funnel shaped hole right through the enamel.
15) MY PROBLEM IS DUE TO MUSCLE SPASM - Highly unusual. A spasm of a muscle is a full contraction, like a full force clench. This occasionally happens during extreme bruxism, but it is rarely the cause of a TMJ disorder, where the muscles have chronically increased tonus rather than occasional spasm. The cause of the build-up of waste products that produces pain in the craniofacial muscles is the sustained compression of the capillary beds by the increased resting tonus, not a spasm.
16) MY PROBLEM IS DUE TO HYPERMOBILITY, SUCH AS EHLERS-DANLOS SYNDROME - Also doubtful. Joint hypermobility can make the disk dislocate more easily than it would if the ligaments that hold it in place were tighter, but subsequently it no longer contributes to the problem. There was a phase about two decades ago when dental researchers thought joint hypermobility was part of the cause of the problem, and TMJ journals showed dentists how to assess general joint hypermobility; but researchers found no real correlations between TMJ disorders and joint hypermobility.
17) DUAL BITE IS A PATHOLOGY - No, dual bite occurs when your mandible creates an additional stable bite in a position more comfortable tahn teh one produced by your "centric relation" bite. The dual bite was considered a pathology when dentists assumed that the only correct bite was the one at the very back of the dentition, in centric relation.
18) SUDDEN LOSS OF CONDYLE HEIGHT, RESULTING IN AN OPEN BITE, REQUIRES SURGERY - No. Sudden loss of condyle height, resulting from rapid TMJ inflammation like an injury or a bout of rheumatoid arthritis, can cause the whole mandible to rotate down and back around the second molars. The rapid backward rotation of the mandible produces excessive anterior vertical face height, which stretches the jaw closing muscles and thereby increases the compressive forces in the TMJs, which tigger more cell damage, creating a vicious cycle. Treating the problem requires restoring acceptable facial height, usually by shortening the second molars.