Journal of Dental Research, Vol 71, 1350-1354, Copyright © 1992 by International & American Associations for Dental Research Online Journals
The effect of orthodontic retention on the mechanical properties of the periodontal ligament in the rat maxillary first molar
R. K. Hong, A. Yamane, Y. Kuwahara and M. Chiba
Department of Pharmacology, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
The load-deformation curves obtained by extraction of the rat maxillary
first molar from its socket in the dissected jaw were analyzed so that the
effect of orthodontic retention on the mechanical properties of the
periodontal ligament could be examined. An elastic band was inserted
between the rat maxillary first and second molars for four days, and then
the interdental space was filled with resin for four or eight days. The
average interdental spaces between the teeth ranged from 315 to 398 microns
during the experimental period. The maximum shear load, elastic stiffness,
and failure energy in shear decreased markedly following application of an
orthodontic force, but they increased gradually and reached control levels
on the 8th day after the retention. Maximum shear deformation at maximum
load was not significantly different between the experimental and control
teeth during the experimental period. It is suggested that, following
orthodontic tooth movement, occlusal function was restored after a
relatively short retention period, as was the impaired mechanical strength
of the periodontal ligament.
