MAXILLARY MOLAR EXTRACTION CAUSES INCREASED BONE LOSS IN THE MANDIBLEOF OVARIECTOMIZED RATS

Although osteoporosis is a major public health concern, its effect on oral bone has not been determined. More important may be the effect of estrogen depletion on the response of oral bane to dental treatments such as tooth extraction or pathologic processes such as periodontal d isease. Our objective was to determine if maxillary molar extraction i ncreases mandibular bone loss in the ovariectomized compared with a sh am-operated control. Fifty-three ovariectomized and 53 sham-operated 6 -month-old Sprague-Dawley rats were randomly assigned to the following groups: (1) ovariectomized, adult; (2) sham-operated, adult; (3) ovar iectomized, adult, extraction; (4) sham-operated, adult, extraction; ( 5) ovariectomized, old; (6) sham-operated, old; (7) ovariectomized, ol d, extraction; and (8) sham-operated, old, extraction. Fourteen days f ollowing ovariectomy, the extraction groups had their bilateral maxill ary molars extracted. The adult and old rats were sacrificed 114 and 2 00 days postovariectomy, respectively. The right mandible was tested t o failure in three point bending. The bone mineral density (BMD) of th e left mandible was measured with high resolution dual energy X-ray ab sorptiometry. The area fraction and area moment of inertia of mandible sections were determined using image processing software. In the ovar iectomized rats, maxillary molar extraction resulted in decreases (p < 0.05) in the failure load (21%), stiffness (39%), BMD (3%), and bone area fraction (8%) of the mandible. However, in the sham-operated rats , these decreases following maxillary molar extraction were less (p < 0.05) than those in the ovariectomized rats and only present in the ma ndibles of the aged rats. Therefore, maxillary molar extraction result ed in a more rapid decrease in structural properties and BMD and a lar ger decrease in bane area fraction of the mandible in ovariectomized r ats compared with those in sham-operated rats. These findings indicate that oral bone loss that occurs as a result of pathologic conditions or dental treatments may be accelerated in individuals who have estrog en depletion.