A longitudinal study of rest position and centric occlusion

A fifteen-year longitudinal study of rest position and centric occlusion was done on sixteen dentulous subjects with random occlusions. In reviewing the literature the author could find no other investigation with this number of years interim. Records consisted of lateral cephalometric roentgenograms taken when the patient was in rest position and in centric occlusion. Rest position was determined by the patient saying "m" and swallowing, and electromyographically when the anterior belly of the digastric and the temporalis muscles elicited the electrical activity. Both linear and angular measurements were made. The figures from 1958, 1959, and 1960 were averaged and compared with the mean of those taken in 1973. Rest position was found to have a small range of stability in all subjects, while the vertical dimension of centric occlusion increased in ten subjects, decreased in two, and remained the same in four.