Effect of increasing vertical dimension on the masticatory system in subjects with natural teeth

Abstract

M any studies show that the postural (rest) position of the mandible changes subsequent to dental attrition, loss of teeth, and prosthetic treatment.’ ’ Immediate changes of the mandibular posture may also be achieved in many ways, e.g., by changing the occlusal vertical dimension both in subjects with natural teeth and in those with complete dentures, by placing or removing dentures in edentulous subjects, by muscular fatigue,“-” or simply by changing the position of the head. In spite of these findings, which demonstrate an adaptability of the mandibular posture to changes in occlusal vertical dimension, the concept of constancy of the rest position has not been abandoned by all authors. Increasing the vertical dimension of occlusion is therefore often held to be a hazardous procedure in prosthetic treatment.“-” Results of experiments that increased vertical dimension both in subjects with natural teeth and with complete dentures have been interpreted as deranging the function of muscles and joints of the masticatory system.’ Clinical experience, however, supports the opinion that the masticatory system adapts well to moderate changes in the occlusal vertical dimension, “’ The present study was designed to test the effect of increasing the vertical dimension of occlusion by a modification of the method used by Christensen.’ Electromyography was added to the methods of