[Parafunctions of the stomatognathic system: their origins and consequences. 1].

Parafunctional activities are mainly responsible for the disorders that are detected in the Stomatognathic System. Those activities have two majors etiological factors, one of those is the occlusal relationship, and the other one is the emotional strain. Muscular hiperactivity role and their mechanics, as a factor of risk in the disorders of the masticatory system, are explained.