THE BAD NEWS
Sometimes it seems like the treatment a patient receives depends on where the elevator stops in the medical dental building. The many misconceptions that have permeated the literature around TMJ disorders for decades have created so much confusion that the dental associations have been unable to agree on regulations or even guidelines.
One result of the lack of regulation is that any dentist can declare expertise in treating TMJ disorders. Many of these self-proclaimed experts have completely different treatment philosophies. Some treat the occlusion, and some warn that the occlusion should never be treated. Most advocate only one type of oral appliance. If that appliance is ineffective, oral appliance treatment is abandoned, even though different types of appliances have completely different effects. Patients with jaw muscle tension in response to an inflamed TMJ often have their jaw muscles treated without distracting the inflamed joint to remove the source of the jaw muscle tension, like massaging the sore tired leg muscles of someone walking around on an inflamed ankle without providing a brace to prevent further stress to the leg muscles after they get off the massage table and start walking again.
The lack of regulation also makes dentists easy targets for all kinds of gadgets that purport to help treat TMJ disorders but have never been shown to be clinically effective. These include a wide range of diagnostic tools such as TENS, doppler auscultation, joint vibration analysis, sonography, thermography, surface EMG, jaw tracking, and TEK scan bite analysis. One prominent surgeon (Piper) advocates using expensive diagnostic tools (MRI) to look for avascular necrosis (AVN) of the condyle, even though research has shown that AVN of the condyle is a rare condition and the diagnosis is unlikely to affect any treatment except surgery.
Treatment modalties are even more varied and often not related to the diagnosis. Botox is becoming a popular treatment option. Studies in rats with experimentally produced jaw injuries have shown that it has some anti-nociceptive effects. In TMJ disorder patients it works primarily by weakening the jaw muscles. In this manner it can produce short term relief in some chronic migraines and dystonia, however weakening the jaw muscles limits their ability to regulate subsequent (adult) facial growth and thereby eliminate the ultimate source of the strain. NTI appliances are easily fabricated and aggressively marketed for treatment of TMJ disorders, although they can destabilize occlusions and they should not be used in the presence of TMJ inflammation. Some myofunctional therapists blame lowered tongue posture on a short lingual frenum and advocate frenectomy, however the short frenum is unlikely to be a primary cause. Other myofunctional therapists blame failure of the front teeth to meet (open bite) on a tongue thrust during swallowing, although research has shown that it is the resting posture of the tongue between the front teeth rather than the intermittent pressures of a tongue thrust during swallowing that causes the problem. The Buteyko breathing method focuses on the posture of the tongue and strengthening the tongue but ignores strengthening the elevator muscles; although it is the strength of the elevator muscles that determines the facial growth pattern, and the mandible forms the base of operation for the tongue, which has no bone of its own.
Well meaning general dentists can hear so many differing opinions from so-called experts that they do not know what to think. They either avoid treating the problem or treat it in the most careful way possible, often including multiple tests and imaging that make them feel like they are being thorough and also legally protected, even though the results of the tests are extremely unlikely to affect the choice of treatment.
THE GOOD NEWS
Fortunately TMJ disorders are self-limiting. Longitudinal studies of tens of thousands of untreated patients have shown that their symptoms disappear over time, especially by middle age. Older people only develop and sustain serious chronic pain conditions involving the TMJ when the condition is maintained by extreme loss of vertical dimension, a systemic condition like rheumatoid arthritis, or complications resulting from failure of a previous open surgery. If previous TMJ degeneration has destabilized the occlusion of an older person, it usually just needs restabilizing. In a sense, the door just needs to be reshaped to fit the hinges.
OCCLUSION is a big source of the confusion regarding TMJ disorders. Advocates of centric relation change the occlusion by retruding the mandible. Advocates of "neuromuscular dentistry" change the occlusion by protruding the mandible. Most dental authorities warn against any changes in the occlusion, because there is no good evidence that occlusion has any bearing on the problem. However, there is no good evidence of a relationship between dental occlusion and anything else, because we cannot even measure any functional aspects of dental occlusion. It's the inability of dentistry to understand occlusion, rather than the lack of importance of occlusion in the pathogenesis of TMJ disorders, that is the barrier to the use of occlusal therapy in the treatment of TMJ disorders. The role of occlusion in TMJ disorders is explained in great detail with extensive footnotes in the OCCLUSION files.
APPLIANCE DEPENDENCE is a common problem for patients who have been left wearing an oral appliance day and night, because the teeth of the opposite arch shift until they fit the surface of the appliance rather than the surface of the opposing natural dentition. Then, when the patient removes the appliance, there is no stable occlusion. A new one can be created with prosthodontics or functional orthodontics, but such extensive dental work often represents a large expense that was necessitated only by the effects of full time appliance wear.
LOWER NIGHTGUARDS can destabilize bites in people with class 1 and class 2 occlusions much like furll time wear of any oral appliance explained above, because nocturnal bruxism that is forceful enough to depress the teeth usually occurs when the mandible is located posteriorly and thereby cannot apply any axially directed occlusal forces to the anterior teeth. With all the forces of nocturnal bruxism concentrated on the posterior teeth, the molars can intrude into the jawbones, and the anterior teeth can extrude (supererupt); thus destabilizing the occlusion by increasing the overbite. In extreme cases, this process can produce a posterior open bite.
UPPER NIGHTGUARDS rarely destabilize bites unless they fail to extend to the terminal molars and thereby function as partial coverage appliances, but they are still designed to protect the teeth rather than the joints. They normally provide bilaterally stable occlusal contacts in or close to centric relation and anterior guidance during all excursions away from that mandibular position, because that is the only way dentists are taught to design an occlusal surface. The primary effects of such nightguards are just increasing the vertical dimension and thereby slightly altering the fully seated positions of the condyles. If the fully seated position of a condyle was impinging on the inflamed tissue, the slight altering of condylar positions could provide relief by shifting the pressure point onto healthier tissue.
ORTHODONTICS is frequently chosen by dentists for their patients but poorly understood. Many dentists perceiving a possible occlusal problem in any patient always refer the patient to an orthodontist, because they were taught in dental school that the best occlusion is one produced by good orthodontics. However, most orthodontics in the United States is esthetic orthodontics - braces or invisalign. By fixing pre-fabricated arch wires into brackets located on the exact center of each tooth, every aspect of torque and angulation can be controlled until the teeth become aligned just like a textbook. The uppers can be aligned perfectly, and the lowers can be aligned perfectly. Alignment with invisalign is less precise but more tolerable. However, with both these orthodontic techniques, there is very little ability to control the mandibular position at which the teeth end up interdigitating, a key feature in the development of TMJ disorders. Even the midlines cannot be easily aligned with any precision.
THE MAIN DISADVANTAGE of esthetic orthodontics is that it has the unintended consequence of limiting jaw muscle use and thereby also limiting jaw muscle development. The jaw muscles regulate facial growth. Strong jaw muscles increase occlusal stability and diminish the asymmetrical retrusive facial growth patterns that frequently produce TMJ disorders. Braces cause a loss of mandibular elevator muscle forces automatically in response to the sore teeth that result from each tightening of the arch wires and the occlusal instability that results from active tooth movement. Invisalign also discourages forceful chewing, although usually for a shorter time period. In addition, these orthodontic techniques are usually employed during the pubertal growth spurt when the jaw muscles should be undergoing their most rapid development and therefore are most vulnerable to growth disruption.
NEW POPULAR ORTHODONTIC TECHNIQUES generally recognize the problems caused by traditional orthodontics that retrudes the mandible and limits facial development. Orthotropics understands the importance of expanding palates and advancing mandibles, but it ignores the role of mandibular elevator strength in controlling facial growth and tongue position. A palatal expansion device called a DNA appliance is being marketed to treat sleep apnea based on claims that its effect is epigenetic and biomimetic, with finger springs that are "responsible for the genetic signalling that helps the body bring the arch into the proper form"; although there is no evidence or likelihood that they can change genetic expression. Furthermore, any effect the appliance might have on relieving sleep apnea is bound to be small, because it alters the structure of the nasal airway while the blockage in sleep apnea is in the pharyngeal airway. Advanced light wire functional (ALF) appliances are gentle palatal expanders promoted based on their supposed ability to enhance the cranial respiratory circulation (discussed further below).
NON-DENTAL TREATMENT is also very variable. Chiropractors may treat TMJ disorders by adjusting the cervical spine, manually distracting the TMJs, myofascial release, or applied kinesiology (AK) to determine the ideal bite position. Physical therapists rehabilitate muscles and joints using various electrical and thermal modalities as well as exercises and stretches. Massage therapists can restore resting circulation in muscles or forcefully compress trigger points to release muscle tightness. Physicians usually treat TMJ disorders the same way they treat acute injuries - medications and rest of the affected part, in this case a soft food diet.
CRANIAL OSTEOPATHY treats TMJ disorders by using light manual pressure to manipulate the skull in order to free up perceived blockages to a hypothesized rhythmic pulsing of the skull bones due to the production of cerebrospinal fluid. The underlying theory (cranial respiration) was developed more than 100 years ago when an osteopath named William Sutherland looked at the remarkable way the cranial sutures fit together and concluded that they must be designed to support movements that circulate cerebrospinal fluid. Since then, catheters inserted into the cranium and spinal cord have shown that cerebrospinal fluid pressue changes depending on body posture and gravity. Also high precision ultrasound has shown that the skull is not a rigid container. It changes shape when a person bends down, and it probably responds to arterial pulsing as well as stresses and strains generated by muscles that may stimulate drainage like the way the lymphatic system works. However there is no evidence to support the idea that there is a unique and distinct cranial respiratory rhythym due to production of cerebrospinal fluid. The cranial sutures were designed to allow the cranium to deform while passing through the birth canal and rebound later. Then they become growth centers that create just enough new bone to continue perfectly enclosing the expanding brain. When cranial bones fail to rebound properly after birth, they can create obvious deformities due to craniosynostosis. Some babies may have partial craniosynostosis that might be correctable with manual manipulation.
The cranial bones obviously have some mobility. In adults, light manual pressure may be able to slightly alter their configuration, and the brain is likely very sensitive to small changes in the configuration of its container; but any alteration of cranial bone configuration that could be produced by light manual pressure would be dwarfed by the effects of chewing and swallowing. These normal functional activities spread very large forces over the whole front of the cranium hundreds of times each day. In monkeys, biting forcefully bends the entire cranium, separating its two halves at the parietal suture. Many pre-industrial humans with strong jaw muscles had a thick ridge of bone along the parietal suture. Modern humans have weaker jaw muscles, but our skulls are also much thinner and therefore more easily deformed by biting forces. The way they stress our crania was illustrated by the Benninghoff diagrams below that were produced by reproducing biting forces in a cranium coated with stress sensitive paint. These stress patterns explain why chewing has been shown to increase cranial blood flow by pumping the craniofacial area.
CRANIOSACRAL ADJUSTMENT has become a popular extension of cranial work that grew out of studies which showed that bending the spine produced changes in intracranial pressure. The spinal column is enclosed in the same CSF fluid reservoir enclosed by the cranium and therefore undergoes the same pressures as the cranium. Some practitioners then reasoned that the spinal column should be subject to the same blockages in CSF flow as the cranium, and they manipulate the spine and skull together. Manipulation that improves the range of motion of a spinal segment is likely to be therapeutic because of the importance of weeping lubrication and circulation at joint surfaces, and releasing blockage to physiologic movements of the spine seems likely to help people, but the focus on a cranial respiratory rhythym seems misplaced.
TIME also resolves TMJ disorders, because most TMJ disorder patients seeking treatment get better no matter how they are treated or even not treated due to the statistical factor known as regression to the mean. In conditions that fluctuate over time, such as TMJ disorders, patients usually seek treatment when their symptoms are especially severe. Thus any subsequent treatment, including simply the passage of time, is likely to bring relief as the symptoms return to their average levels. Dentists and other health care practitioners who provided treatment when the patient was most in need can easily become convinced that the treatment they provided was responsible for the relief, even if it had no actual effect on the condition. Such experiences can lead to claims that TMJ disorders can be cured by anything from braces to Reiki.