Many hypotheses concerning the relationships that might exist between the disorders of masticatory system or temperomandibular disorders (TMD) and malocclusions have been advanced. But, in terms of evidence-based medicine, can we say that any of them have scientific merit?

The objective of our project was to analyze the existing international literature of the years 2000 to 2009 on the relationship between malocclusion and malfunction of the masticatory system.

Materials and method: we used MEDLINE to find all papers written in French or English that had an abstract referring to “Malocclusion” and “Temperomandibular joint disorders.” We subjected them to a critical analysis using a reading record program that sorted the papers into types of study, descriptive or analytical, and the intensity of their methodology. Two of our authors calibrated this analysis and we compared their results.

Results: We examined 17 studies out of a panel of 171 articles. Nine out of the seventeen were transverse studies, six were longitudinal studies, one evaluated cases and a control group, and one was a cohort study. An ethical committee had approved of 9 of the studies and 9 out of the group had been randomized. From all seventeen we collected calibrations from observers and made statistical analyses of the data.

Our conclusion was that there is a relationship between malocclusion and TMD but that it is a weak one.

The results of the different studies varied considerably as a factor of the type of malocclusion incriminated and the type of temperomandibular disorder reported. Our work indicated that a relationship between TMD and malocclusion cannot be established and the studies we reviewed had little scientific value primarily because of the heterogeneity of the samples and of the lack of clearly established definitions of the terms “malocclusion” and “disorder” of the masticatory system.