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 ovariec tomized rat as a model, we examined whether acute estrogen depletion a ffects the mandible of the ovariectomized rat with and without maxilla ry molar extraction. Twenty-two ovariectomized and 20 sham-ovariectomi zed 90-day-old Sprague-Dawley rats were divided into the following gro ups: (1) sham-ovariectomized, baseline control; (2) ovariectomized, ba seline control; (3) ovariectomized; (4) ovariectomized, tooth extracti on; (5) sham-ovariectomized; and (6) sham-ovariectomized, tooth extrac tion. On day eight, sham-ovariectomized and ovariectomized rats had al l their maxillary molars extracted, and the baseline control sham-ovar iectomized and ovariectomized rats were killed. On day 35, the remaini ng animals were killed. After teeth were harvested, the right mandible was tested to failure in three-point bending. The bone mineral densit y of the left mandible was measured with dual-energy x-ray absorptiome try. The area fraction and area moment of inertia of a section of mand ible were determined. Neither ovariectomy nor tooth extraction signifi cantly affected the bone mineral density or structural properties of t he 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 n ot do so in the sham-ovariectomized rat.