Quantitative radiographic changes in the mandible, femur and vertebra in lactating rats fed a low-calcium diet.

OBJECTIVE

To determine whether similar changes occur in the mandible, femur and vertebral body in generalized osteopenia.

METHODS

Osteopenia was induced in the bred animal group using a low calcium diet from parturition onwards. Control groups were virgin and bred rats fed a normal diet. Rats in each group were weighed weekly, and subgroups of 12 rats in each treatment group were killed at ages 18, 24, 36 and 48 weeks. A separate reference group of 12 rats was killed at age 12 weeks, i.e. day 0 of the comparative study. The mandibles, both femurs and the first lumbar vertebrae of all rats were removed post-mortem and radiographs made for each individual bone; measurements of cortical thickness and bone widths were made from these radiographs using a computer-based video image analysis system.

RESULTS

Significant differences among treatment groups were detected for each bone type; changes were sustained over the 48-week study period for the femur and vertebrae but were transient, except for alveolar bone height, in the mandible. Significant differences were found for cortical thicknesses and bone widths in the mandible, femur and vertebrae, based on the duration of the low-calcium diet. Although significant differences in the thickness of some cortices were found in the mandible, dimensional changes were small.

CONCLUSIONS

Mandibular cortical width is an unreliable indicator of osteopenia in this rat model.