| Societal Etiology of TMJ Disorders |
| Written by Dr. John Summer, TMJ Expert, Portland, Oregon |
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THE FOLLOWIG TEXT IS AN EXCERPT OF A VOLUME ENTITLED "SOCIETAL ETIOLOGY OF TMJ DISORDERS." The full volume is available for download using the link below. TMJ disorders are a product of modern civilization. In the thousands of intact human skulls in museums and also in the few tribes still living traditional life styles today, we can see some evidence of arthritic degeneration of the TMJs associated with extreme tooth wear, but we find no evidence of the dislocated disks, strained bites, or asymmetrical retrusive verticalized facial growth which frequently characterize modern TMJ disorder patients. Stress is a contributing factor because it causes tightening of all the skeletal muscles, and jaw muscles which are already tight from chronically bracing to protect a damaged TMJ are easily pushed by additional tightness from a state of borderline circulation to a state of insufficient circulation. However stress is not the primary cause. The effect of environmental pollution and allergies on head posture and thereby on facial growth is another potential contributing factor in some people. However it also is not the primary cause. The primary cause is our recent dietary change to sweetened refined foods and the way the resultant loss of functional chewing forces has affected craniofacial growth. The human chewing system was designed to adapt its growth to the functional demands imposed in it and thereby achieve a structure customized to best fit the conditions under which it would operate. The bones supporting the upper and lower jaws grow by very different mechanisms, and their growth needs to be coordinated by each of the involved bone growth processes accomodating the same normal functional range of motion. The result was a functional harmony which was established early in life and then gradually changed with age in a way that made it progressively more compatible with the changes which simultaneously take place in all aging tissues. As the bite table and TMJ contours became flatter and jaw movements became longer and steadier; chewing stresses to bones and joints became rhythmic and wavelike, protective neuromuscular reflexes became quiescent, muscle firings provided ideal exercise in the form of strong smoothly alternating firings of agonists and antagonists, and bite forces provided circulation by pumping the teeth rhythmically up and down in their sockets. Recently our transition to sweetened refined foods has made jaw muscles weaker and jaw movements narrower so they are no longer as able to regulate craniofacial growth. Our steep irregular bite tables are covered by unworn vertical surfaces which lock the upper and lower jawbones together (maxillo-mandibular synostosis) by means of deep interdigitation, a steep curve of Spee, and an overbite that is retained throughout adulthood. These changes have altered facial growth by restricting forward translation of the lower jawbone and circumferential expansion of the upper jawbone. Growth has been redirected vertically. One result is that, on average, our faces grow narrower, longer in front, more asymmetrically, and more retrusively than they used to – sometimes producing facial shapes that were never seen before the last century. Similar alterations of facial growth have been produuseced in laboratory animals by softening the diet or by cutting or removing jaw muscles. In addition, because many of the adaptive mechanisms relied on functional stimulation, our faces frequently grow without the benefit of sufficient adaptive capacity to eliminate those stresses and strains and thereby achieve the goodness of fit which is usually seen in other musculoskeletal system components. Because facial growth continues throughout life, adaptation may never catch up. To understand how this situation has occurred requires first looking at how the human chewing system evolved to acquire functional harmony and then at how this process has been changed by the softening of our food to create a functional disorder. To understand how to correct the situation requires then using that information to learn how we can establish a new functional harmony which can be maintained in our modern human chewing systems.
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