Mandibular bone loss in an animal model of male osteoporosis (orchidectomized rat): a radiographic and densitometric study.

In humans, hypogonadism is associated with osteoporosis and can be studied by densitometry (DXA) on the vertebrae or long bones. There is some controversy about the relationships between bone loss in these sites and in the mandible. Osteoporosis has been suggested as a risk factor for dental problems. In the rat, orchidectomy (ORX) is associated with an increased bone resorption resulting in bone loss. We have studied the time effects of ORX on the alveolar bone in the rat. Forty-eight male Wistar rats were divided into four groups and studied over 2, 4, 8 and 16 weeks. In each group, six rats were ORX and six sham-operated (SHAM) animals were used as control. The mandible of each rat was dissected. Numeric radiographs, centered on the molar region, were obtained. Bone loss was observed qualitatively at 16 weeks in ORX animals. Quantitative modifications were confirmed by texture analysis of numeric radiographs using the run-length technique. The bone mineral content (BMC) and density (BMD) of the hemimandible and in a region centered on the molars were measured by DXA. The coefficient of variation (CV) for BMC was poor on the whole bone and no differences could be observed even at 16 weeks. For BMC of the molar region, the CV was improved and significant bone loss occurred in the ORX group at 16 weeks ( P<0.016). This study confirms that in the male rat, the reduction of sex hormones induced by ORX is associated with a decrease in bone mass in the mandible.