An evolutionary perspective on craniomandibular dysfunctions

Abstract

Craniomandibular dysfunctions (CMDs) are a set of clinical disorders affecting mostly the masticatory muscles and the temporomandibular joints manifesting as pain syndrome, functional limitations, and hard and soft tissue degeneration. CMDs have a high impact on the patient’s quality of life as they limit important functions such as chewing and deglutition, respiration, speech, and social interactions. In industrialized societies, the incidence of CMD patients needing treatment is estimated to be about 5%, where females show at least twice the prevalence of males. An excursus through anthropological, clinical, and biological evidence can help elucidate the evolutionary origin of CMD and evaluate the effects of modern lifestyle on the health and function of the stomatognathic system.

To demonstrate CMDs as diseases of civilization, it should be shown that cultural and technological changes have affected the orofacial structures and that these changes have functional implications that are, in turn, causal to CMDs.

Compared to pre-industrial populations, contemporary modern humans are characterized by smaller, retrognathic mandibles, with narrower dental arches and deeper palates. Anthropological and experimental animal research has shown that such changes are associated with a highly refined diet, typical of post-industrial societies. The functional implications of these morphological changes can be postulated based on a theoretical framework and are supported by experimental and clinical studies.

CMDs’ etiological factors have long been discussed in medical settings, however, occlusion's role in the onset and maintenance of these disorders is controversial. Yet, the interrelationship between the morphology of the masticatory structures and CMDs can be elucidated by deductive reasoning upon the available anthropological, clinical, and biological evidence.