Occlusion and temporomandibular disorders (TMD): still unsolved question?

Sufficient Cause vs. Causal Factor Clark’s (1991) comment that “a high percentage of patients who have a naturally occurring ‘occlusal abnormality’ do not exhibit TM disorder” discloses that a distinction between the concepts “sufficient cause” and “causal factor” has not been made. This criticism applies also to the review by DeBoever et al. (2000). The conclusion should have read: “The literature does not give strong support for the opinion that occlusion is a sufficient cause for TMD.” (emphasis added) All diseases and disorders are multifactorial in practice. The most common example in dentistry is dental caries. Not mutans streptococci alone and not a sugar-rich diet alone lead to dental decay; they are both needed in addition to a certain weakness in host resistance. Analogously, if both stress and occlusal factors are needed for TMD to develop, then occlusal factors are a causal factor but not a sufficient cause for TMD. Occlusion could be excluded as a causal factor if the absence or presence of occlusal interferences does not affect the incidence rate of TMD in longitudinal studies (Kirveskari et al., 1998).