As a dentist who has been in the field of dental occlusal research, temporomandibular disorders (TMD), and lately, dental sleep apnea, it is often puzzling to me how so many of my colleagues could be at odds when it comes to the role of dental occlusion on these disorders. Having treated private patients over a 40-year span while also teaching at a major dental school over these years, I have come to appreciate that scientific evidence does not always support our clinical gut.
Having looked at the results of studies conducted by respected colleagues on both sides of the aisle, I have come to the conclusion that we all seem to be looking at the same elephant from different viewpoints, and where the failure of agreement lies is not in the evidence but rather in the way our evidence is collected.[Citation1–4]
An example of this was a study to look at bruxism and its effect on tooth wear, periodontal disease and TMD.[Citation5] We found that severe bruxism could lead to different effects in different patients. In some, there was tooth wear, and in others it was jaw and muscle pain, while in still others, there was an inverse relationship between bruxism and periodontal bone breakdown. In none of the subjects studied was breakdown evident in all three areas in the same individual. We called it the ‘weak link theory,’ suggesting that if a study only looked at one outcome, the resulting conclusions may be different from one that looked at the same level of bruxism on multiple outcomes in the individual subjects studied.[Citation5]
The term ‘dental occlusion’ seems to be loosely applied to the wide range of concepts in the field and may be the reason why there is such misunderstanding and disagreement between occlusal concepts.[Citation1–4] Is it tooth related [Citation6]; muscle related [Citation7]; joint related [Citation1,8]; or is it something else completely?
Literature seems to support a concept of a 3-D maxillomandibular relationship, which affects the placement of the temporomandibular (TM) joints and head and neck in the same position, where the mandible is stabilized by the muscles that move and support it during wakefulness and sleep. The concept of an ‘occlusal fence’ with the maxilla either constraining the mandible or allowing it to be ‘free’ during growth and development and into adulthood may be a better way to understand the role of arches as being functional dental occlusion vs. the individual tooth contacts we currently employ for the term.[Citation9]
This would explain and allow the variety of concepts of anterior posterior jaw position (centric relation (CR), centric occlusion (CO), and neuromuscular) lateral jaw position and movements and vertical dimension to be distilled into one understandable whole, while still incorporating the role of head and neck relationships during awake and sleep postures.[Citation10]
Maybe ‘dental occlusion’ is a term that should no longer be used in the context of sleep dentistry and TM disorders; rather we should refer to these complex postural positions as maxillomandibular interrelations.
Tufts Craniofacial Pain Center, Boston, MA, USA
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References
- Dawson P. Functional occlusion: from TMJ to smile design. St. Louis (MO): Mosby Elsevier; July 2006.
- Jankelson B. Neuromuscular aspects of occlusion: effects of occlusal position on the physiology and dysfunction of the mandibular musculature. Dent Clin North Am. 1979;23:157–168.
- Turp JC, Greene CS, Strub JR. Dental occlusion: a critical reflection on past, present, and future concepts. J Oral Rehabil. 2008 June;35:466–553.
- Roth RH. The maintenance system and occlusal dynamics. Den Clin North Am. 1976;20:761–788.
- Mehta N, Forgione A, Maloney G, et al. Different effects of nocturnal parafunction on the masticatory system: the weak link theory. Cranio. 2000;18:280–285.10.1080/08869634.2000.11746142
- Ramfjord S, Ash M. Occlusion. 2nd ed. Philadelphia (PA): W. B. Saunders Company; 1971, p. 67.
- Jankelson RR. Effect of vertical and horizontal variants on the resting activity of masticatory muscles. Anthology of ICCMO. 1997;IV:69–76.
- Pokorny P, Wiens J, Litvak H. Occlusion for fixed prosthodontics: a historical perspective of the gnathological influence. J Prosthet Dent. 2008;99:299–313.10.1016/S0022-3913(08)60066-9
- Mehta N, Abdallah E, Lobo-Lobo S, et al. Three–dimensional assessment of dental occlusion (occlusal fencing): a clinical technique. Inside Dentistry. 2006;2:28–36.
- Häggman-Henrikson B, Nordh E, Zafar H, et al. Head immobilization can impair jaw function. J Dent Res. 2006;85:1001–1005.10.1177/154405910608501105