I want to thank the editor of the AJO-DO for inviting me to respond to the essay by Professor Rudy Slavicek. Unlike him, I won’t be starting at the time period of 5 to 6 million years ago. Instead, I want to focus on the current situation in the orthodontic field in regard to disorders of the masticatory complex and adjacent structures; these usually are collectively described as temporomandibular disorders (TMD). However, I noticed that Professor Slavicek used this term only twice in his essay.

My main concern for many years has been the role that orthodontists think they should play in dealing with various types of TMD. As Okeson pointed out, “It is difficult to imagine a specialty that routinely and significantly changes a patient’s occlusal condition would not have a powerful effect on the masticatory structures [eg, the temporomandibular joints (TMJs)] and their functions.” This obviously correct observation has, in my opinion, been used to justify both appropriate and inappropriate behaviors by orthodontists as they encounter TMD in their practices. The need for orthodontists to constantly monitor and evaluate the relationships between their occlusion-changing procedures and the well-being of the TMJs cannot be disputed; it is the very essence of their daily work. As I like to tell my orthodontic students, “You are in the occlusion-disrupting business, so you must have reasonable treatment objectives and procedures to move every patient’s dentition to a new set of occlusal and craniomandibular relationships that will be biologically acceptable.”

However, the above truisms do not automatically translate into a conclusion that failure to produce some expert’s version of a good occlusal or craniomandibular outcome is a risk factor for developing TMD. Furthermore, it does not mean that an untreated person with a malocclusion or a nonideal TMJ relationship (whatever that means) is at risk for developing TMD. Finally, it does not mean that patients with active TMD symptoms and craniomandibular or occlusal imperfections will need orthodontic treatment to become healthy. If TMD symptoms arise during active orthodontic treatment, it is possible that the mechanical forces and transient occlusal mal-relationships have exceeded that patient’s capacity for adaptation, but it is even more likely that some adolescents and young adults treated by orthodontists will simply develop TMD coincidentally during the 2- to 3-year period of treatment.

Interestingly, I find myself in agreement with many of the points raised by Professor Slavicek, although I disagree with others. In his section on “First period of the mixed dentition,” he correctly stated that eruption of the first molars and exchanging deciduous anterior teeth with the permanent ones will set the table for structural adaptations of the TMJ; as he concludes, “This means that occlusion dictates adaptation.” In a later section on “Functional period of maturation,” he correctly stated that “the position of the mandible is determined 3 dimensionally by the occlusion of the teeth.” However, it is at that point that he and I might differ in our interpretations of those facts. He seems to regard the mandibular position as fragile and intolerant of phenomena such as so-called functional interferences in occlusion (or the disruption produced by orthodontic treatment). I was glad to see that he devoted only 1 sentence to the proposition that “Avoidance patterns [elicited by functional interferences] . . . might be 1 reason for” TMD. This notion goes back over 75 years, and, despite the overwhelming evidence against it, we still hear it repeated constantly in the TMD field.

However, my 45-year background in the TMD field leads me to believe the TMJ is remarkably resilient and capable of putting up with a lot of diverse dental concepts and procedures. It is this very resilience that makes it possible for dentists to create regional crowns and bridges as well as full-mouth reconstructions, while orthodontists and orthognathic surgeons produce even more massive occlusal changes either slowly or quickly. Not only are these major interventions, but the concepts for carrying them out can differ quite a lot from 1 dentist to another (not to mention between 1 expert and another). Yet, most patients “adapt” to the various versions of how these procedures are carried out; this is a tribute to the body’s ability to regain homeostasis, but some dentists seem to be unable to accept this fundamental biological concept when it comes to the TMJ.

The main points advanced by Professor Slavicek that I disagree with are to be found in his section on bruxing and clenching, which has a subheading, “the role of teeth in stress management.” To his credit, he did not invoke the old concepts of occlusal disharmonies being responsible for causing these parafunctional activities. However, his statements about reducing stress through bruxism or using the masticatory organ as a psychic stress valve are based on outdated ideas about that relationship, as are the rather old literature references that he cites. Therefore, his final sentence in that section (“Grinding and clenching are expressions of psychic stress assimilation and are mainly controlled by the neuromuscular system and occlusion.”) is no longer regarded as a correct theory, although psychologic factors can play a role in awake bruxism. Instead, during the past 20 years, research in this field has been conducted primarily in sleep laboratories, where it has been shown that significant nocturnal orofacial parafunctions (sleep bruxism) are part of a disordered sleep cycle, and they are now labeled as parasomnias. Space does not permit a full discussion of this topic here, but readers will be better served by looking into that literature instead of the articles cited by Professor Slavicek.

In the last section of his essay, Professor Slavicek offers a brief summary of “gnathology,” which oddly is referenced only to the article by Rinchuse and Kandasamy that was quite critical of the myths of orthodontic gnathology. His original response to their article was sent to the AJO-DO , which persuaded our new editor to invite him to participate in this Point/Counterpoint. I had expected Professir Slavicek to mount a more vigorous defense of gnathology as an occlusal discipline that was essential for the practice of orthodontics in this section. Instead, he merely offered a few sentences to define the term and to extol its virtues as a major theory of how the masticatory system works and how it should be treated. Although I am not a fan of gnathology as a superior conceptual framework, I do respect the dedication of dentists who follow the gnathologic discipline when they are performing major restorative dental procedures. There is an old joke that compares a gnathologic dental reconstruction protocol to an airplane flying from Chicago to Detroit via Los Angeles; when you get to your destination, everything is fine—but it was a long trip. However, Rinchuse and Kandasamy objected to the inference that the concepts and procedures of gnathology should be viewed as a superior approach for the practice of orthodontics, where no teeth are being structurally altered. In my opinion, their criticisms regarding this issue are well founded, since no evidence either from inside the specialty or from external occlusion authorities has proved the necessity (or even the utility) of following this type of complex protocol during orthodontic treatment.

Finally, the Conclusions section of Professor Slavicek’s essay consists of a series of short sentences that summarized much of what has gone before. I found myself in agreement with almost every one of those statements, because they correctly describe how the masticatory system is built and how it works. Only the last sentence, which links the mouth with the psyche, is somewhat overstated; surprisingly, there is no mention at all of either orthodontic treatment or TMD in this final section. I hope this means that Professor Slavicek and I are closer to some degree of agreement than we might have initially expected. I salute his lifelong dedication to the study and restorative treatment of the masticatory apparatus.