Journal of Dental Research, Vol 65, 1294-1299, Copyright © 1986 by International & American Associations for Dental Research Online Journals
Adaptations in the temporalis muscles of rabbits after masseter muscle removal
P. Guelinckx, P. C. Dechow, R. Vanrusselt and D. S. Carlson
Center for Microsurgery, Universitair Ziekenhuis, Leuven, Belgium.
Masseter muscles were surgically removed in six young female rabbits so
that we could study adaptations of the superficial temporalis muscles (ST)
to increased functional requirements. Eight weeks following surgery, we
used morphological measurements, histochemistry, contractile properties in
situ, and occlusal force in vivo to compare the muscles in the experimental
animals and six control rabbits. Analysis of the results demonstrated a
decrease in fatigability of ST after masseter myectomy. Incisal occlusal
force decreased by 65% during the first two weeks, and no recovery was
observed during the following six weeks. At eight weeks post-surgery, the
mass, twitch tensions, and tetanic tensions of ST were not significantly
different from those of the controls. An increase in the percent of the
cross-sectional area composed of fast fatigue-resistant fibers, a slower
time-to-peak twitch tension, and a decrease in fatigability suggest an
increase in oxidative metabolism. Analysis of these results suggests that
muscles used for highly repetitious activities with submaximal loadings
adapt to increased functional requirements by increasing fatigue-resistant
properties.
