Maxillary molar extraction decreases stiffness of the mandible in ovariectomized rats

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.