Journal of Dental Research, Vol 73, 1735-1741, Copyright © 1994 by International & American Associations for Dental Research Online Journals
Maxillary molar extraction decreases stiffness of the mandible in ovariectomized rats
R. P. Elovic, J. A. Hipp and W. C. Hayes
Orthopedic Biomechanics Laboratory, Beth Israel Hospital, Boston, Massachusetts 02215.
Although osteoporosis is a major public health concern, the effect of this
condition on oral bone has not been determined. Using the ovariectomized
rat as a model, we examined whether acute estrogen depletion affects the
mandible of the ovariectomized rat with and without maxillary molar
extraction. Twenty-two ovariectomized and 20 sham-ovariectomized 90-day-old
Sprague-Dawley rats were divided into the following groups: (1)
sham-ovariectomized, baseline control; (2) ovariectomized, baseline
control; (3) ovariectomized; (4) ovariectomized, tooth extraction; (5)
sham-ovariectomized; and (6) sham-ovariectomized, tooth extraction. On day
eight, sham-ovariectomized and ovariectomized rats had all their maxillary
molars extracted, and the baseline control sham-ovariectomized and
ovariectomized rats were killed. On day 35, the remaining animals were
killed. After teeth were harvested, the right mandible was tested to
failure in three-point bending. The bone mineral density of the left
mandible was measured with dual-energy x-ray absorptiometry. The area
fraction and area moment of inertia of a section of mandible were
determined. Neither ovariectomy nor tooth extraction significantly affected
the bone mineral density or structural properties of the rat mandible.
However, there was an interaction between ovariectomy and maxillary molar
extraction on the stiffness of the rat mandible (p < 0.008). Maxillary
molar extraction decreased the stiffness of the mandible by 25% (p <
0.05) in the ovariectomized rat, whereas it did not do so in the
sham-ovariectomized rat.
