I want to thank Drs Rinchuse and Greene for their article, “Scoping review of systematic review abstracts about temporomandibular disorders: comparison of search years 2004 and 2017” (Rinchuse DJ, Greene CS. Am J Orthod Dentofacial Orthop 2018;154:35-46). This was an interesting way to bring our members more up to date with the plethora of TMD systematic reviews that are now coming out and the implications of the important recent advances in the field. The role of genetics in our understanding and identification of vulnerable patients is an exciting movement. The need to understand and address the chronic pain aspect of TMD patients is especially important for our growing number of adult patients. Taken along with Dr Rinchuse’s cautionary statement, “It is still possible for an occasional orthodontic patient’s TMJ complaint to be caused by treatment,” we need to pay attention to all the evidenced-based information on TMD that will make us better clinicians when it happens and better educators when patients bring up the subject. It was also interesting to find that bruxism is still associated with TMD in 2 studies—some things new, some things old.
There was much focus on occlusion and TMD, which is to be expected with the long history of controversy over the proper understanding of this as an etiologic factor in TMD, and we are in “the occlusion-disrupting business.” To assist the authors in their effort, I want to add 2 systematic reviews from 2017 that escaped their search. I think they may be of interest to our readers.
In contrast to the 1999 and 2004 systematic reviews on occlusion in this summary, a more current, late-2017 systematic review that addressed TMD and occlusion by Manfredini et al found that centric relation-centric occlusion (CR-CO) discrepancies greater than 2 mm and mesiotrusive (balancing) interferences are associated with TMD. This was consistent with the finds of his 2 studies in 2014. In the study that looked at the synergistic relationship of bruxism and CR-CO discrepancies greater than 2 mm, the relationship was even stronger. Overall, their regression analysis of occlusal factors combined with bruxism had a predictive value of 20.4% of the variance for Research Diagnostic Criteria/TMD diagnoses.
In another late-2017 systematic review that looked only at CR-CO discrepancies, the authors found that 11 of 17 nonorthodontic studies and 2 of 3 orthodontic studies showed a relationship with TMD, but the investigations were not homogeneous enough for a meta-analysis. It seems that the concerns of our gnathologic brethren have not been completely put to rest at this time.
A more complete compilation of 2017 systematic reviews shows us that we must still take the advice that Dr Rinchuse gave us years ago: “The evidence-based view on occlusion and TMD does not argue or conclude that occlusion (or condylar position) has no relevance to TMD or that orthodontists should ignore it. What can be gleaned from the evidence-based paradigm is that occlusion is no longer considered the primary and only factor in the multifactorial nature of TMD.” Systematic reviews in 2017 on the subject seem to validate the importance of paying attention to orthopedic instability and lateral guidance, since we have the technology to design these in most of our patients on a daily basis. I hope that some day we will have a better understanding of what occlusal factors are the most significant, and we can better identify less-adaptive patients when they arrive at our offices for treatment. Although our knowledge is incomplete, it seems justifiable to pay heed to Okeson’s caveat: “assuming orthodontic therapy is completely unrelated to TMD is a relatively naïve thought.”
∗ The viewpoints expressed are solely those of the author(s) and do not reflect those of the editor(s), publisher(s), or Association.