As Dr. “Wick” Alexander once put it “For many years, temporomandibular joint dysfunctions (TMD) were a medical no man’s land” [1]. In my opinion, such a situation resulted from a simple fact that it had not been possible to properly visualise temporomandibular joint (TMJ) structures until the introduction of CBCT and MRI in the mid 1980s. We had had a somewhat similar confusion before Holly Broadbent introduced the first cephalometric machine in 1930. As with cephalometrics, it took decades to accrue scientific data in the area of TMJ. Luckily, today we are sufficiently equipped with evidence that can guide our clinical decisions regarding TMJ issues.

One of the most perplexing questions on TMJ was its relationship to occlusion. For a long time, several groups of dentists were preoccupied trying to find an “ideal” condylar position described as “centric relationship” (CR) which was believed to be exactly coincidental with the position of maximum intercuspation (MI) previously called “centric occlusion” (CO). It was postulated that even minor discrepancies between CR and CO will inevitably lead to TMJ problems. Today it has long been understood that healthy individuals show a remarkable variability in the position of TMJ structures.

A few weeks ago, my friend and colleague, a brilliant Canadian orthodontist, Dr. Sylvain Chamberland drew my attention to a recent article published in the AJODO which in an evidence-based manner sums up a long-lasting CR-CO debate. 

In this blog post, I am going to write a brief review of this useful text adding some excerpts from other sources and then formulate my own clinically applicable conclusions.

Temporomandibular disorders and orthodontics: What have we learned from 1992-2022?

DOI: 10.1016/j.ajodo.2021.12.011

Sanjivan Kandasamy, Donald J Rinchuse, Charles S Greene, Lysle E Johnston Jr

The article is written by the group of world-renown experts in TMJ. In their introduction, the authors touches upon the history of CR-CO controversy and mentions Ronald Roth who “played a pivotal role in merging the gnathological-prosthodontic philosophies into orthodontics”. Roth’s main idea was to establish an “ideal” condylar position in the glenoid fossa by the means of mechanical changes of occlusion. In 1970s, he described such a position as posterior and superior, but later, in 1980s, he frivolously changed it to anterior and superior. Today neither of Roth’s beliefs sound scientifically tenable. From CBCT and MRI studies, we now know that healthy individuals may have anterior, centric, or posterior condylar positions [2], whereas every third healthy individual has some form of disk displacement [3]. 

The authors then described the changes that have happened during the “three decades of knowledge”, a period from the early 1990s to the present day. In brief, they write that a large amount of evidence-based data accumulated over that period has helped us to transition from Roth’s mechanical-based approach to a biopsychological model of care. For example, William Arnett and Michael Gunson [4] list the following biopsychological risk factors to TMJ problems: age and gender, systemic illnesses, hormonal imbalances, parafunctions, trauma.

Next, the authors stress the importance of interdisciplinary cooperation with the specialists outside the dental field and go through a number of studies which prove that occlusal adjustments alone do not generally provide a relief of TMD symptoms.  

In their conclusion, the authors mention self-proclaimed experts who encourage orthodontists to treat nonexistent TMJ dysfunctions “taking advantage of the associated short-term financial benefits”. This, in fact, is a problematic trend. However, it seems to me that orthodontic gnathologists have now lost their credibility in English-speaking countries and primarily operate in non-English-speaking parts of the world exploiting the language barrier.

Overall, I find the article a laconic evidence-based bottom line of CR-CO debate. I think that every orthodontist should get aquatinted with it and derive take-away messages for oneself.

If I am asked to pick a single take-away message, it would be this line:

“A patient’s original maxillomandibular relationship with their teeth in MI (ensuring no dual bite present) appears to be the best physiological guide to base treatment on.”

My conclusions:

1. We should evaluate our patients for potential dual bites and screen for TMD symptoms.

2. If no significant dual bite is present, we should not aim to change an original asymptomatic condylar position to a supposedly “ideal”.

3. If we encounter TMD symptoms we should identify potential risk factors and if needed refer to appropriate specialists such as rheumatologists, psychologists, or general physicians. 

REFERENCES:

1. R.G. “Wick” Alexander, The Alexander Discipline, Volume 2: Long-Term Stability, Quintessence Publishing, 2011, p. 41

2. Türp JC, Walter M, The anteroposterior condylar position in maximum intercuspation in the dentate adult. J Craniomandib Funct. 2014;6(1):9–20

3. Tallents RH, Katzberg RW, Murphy W, Proskin H, Magnetic resonance imaging findings in asymptomatic volunteers and symptomatic patients with temporomandibular disorders, J Prosthet Dent, 1996 May;75(5):529-33. doi: 10.1016/s0022-3913(96)90458-8

4. Arenett GW, Gunson MJ, Risk Factors in the Initiation of Condylar Resorption, Seminars in Orthod, Volume 19, Issue 2, June 2013, Pages 55-70. doi.org:10.1053/j.sodo.2012.11.004