Journal of Dental Research, Vol 69, 1776-1779, Copyright © 1990 by International & American Associations for Dental Research Online Journals
Variation of approximal tooth contact tightness with postural change
T. E. Southard, K. A. Southard and E. A. Tolley
Department of Orthodontics, University of Tennessee, Memphis 38163.
In order to investigate the role played by posture in determining posterior
dental contact tightness, we measured contact tightness of maxillary and
mandibular posterior teeth in ten adult subjects, while each was initially
seated upright, after each had assumed a supine posture for two h, and
finally after each had returned to an upright posture for two h. The
technique used for measurement of contact tightness was based on frictional
force concepts and consisted of the recording of the force required to
withdraw a 0.038-mm-thick stainless-steel strip that had been slipped into
each contact. A decreased mean tightness of all maxillary and mandibular
contacts followed the change from an upright to a supine posture. The most
significant decrease (-32%) occurred at the mandibular first molar-second
premolar contact, and the smallest decrease (-10%) occurred at the
mandibular first premolar-canine contact. An increased mean tightness of
all maxillary and mandibular contacts followed a return to an upright
posture. The most significant increase (20%) occurred at the maxillary
first molar-second premolar contact, and the smallest increase (8%)
occurred at the maxillary first premolar-canine contact. We conclude that
posterior dental contact tightness, generally regarded by dentists as a
static feature of occlusion, varies significantly as a function of posture.
