The remodeling of bone during molar drifting and cortical growth in the rat maxilla and the effects of dichloromethylene bisphosphonate (Cl2MBP) on these processes were investigated in 30 age-matched rats. A control group of six rats was killed at 10 weeks of age. Beginning at 10 weeks of age, 12 rats were treated with daily subcutaneous injections of Cl2MBP (10 mg/kg), and 12 control rats were injected daily with normal saline. Six rats of each group were killed at 12 and at 20 weeks of age. All rats were injected with fluorescent bone labels eight and one days before termination. Calcified and decalcified vertical sections through the lingual roots of maxillary molars were prepared for histomorphometry. Bone apposition rates, remodeling activity, and bone cell populations were quantified by image analysis on depository and resorptive surfaces of alveolar bone and on cortical bone surfaces. The drift rates of the first and second molars were calculated. Results showed that in control animals the drift rate of the first molar exceeded that of the second molar (p less than 0.05), supporting a previously proposed mechanism for age-dependent narrowing of interdental bone. Cl2MBP treatment decreased remodeling activity on resorptive surfaces of alveolar bone, despite a transient increase in osteoclasts. Cl2MBP also decreased the osteoblast number and bone apposition rate on depository surfaces of alveolar bone, and reduced the rate of molar drifting (p less than 0.05). However, Cl2MBP treatment had no detectable effect on osteoblast number or bone apposition on cortical bone surfaces. These results support the concept that bisphosphonates influence bone formation indirectly through a coupling mechanism which links formation with resorption.

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Structural and cellular alterations of interproximal alveolar bone were quantified by histomorphometry in 36 Wistar rats over an 18 week period. Half of the rats were fed a standard diet and half were fed a high‐sucrose diet from time of weaning. Six animals from each diet group were sacrificed at 10, 18 and 28 weeks of age, one hour after labeling with tritiated thymidine. Autoradiographs were prepared from histological sections, and the interproximal area between first and second maxillary molars was evaluated, Periodontal ligament width, cell populations and cell proliferation were reduced by 18 weeks of age. By 28 weeks of age, significant reductions of bone dimensions were detected and a further decrease in fibroblast proliferation was evident. The influence of diet on the changes observed was relatively minor. Evidence from this investigation supports the concept that changes in alveolar bone are initiated early in the life span of the rat, and provides a quantitative basis for future use of the rat model in similar studies.

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Iliac trabecular bone sites were studied in 2 male and 2 female adult beagles to determine normal structural variability among different sites, and to identify transilial biopsy sites with minimum structural variation. Only sites that provided adequate amounts of trabecular bone were studied. Trabecular bone area and perimeter were measured on microradiographs of ground sagittal sections using a Quantimet 720 image analyzer, and percent bone, perimeter to area ratio, and mean trabecular width were calculated. Over 100% variation was found in the parameters studies among sections from different sites within the same animal. However, variability was minimal among sections obtained more than 2 mm from the lateral or medial cortex within the most caudal sites evaluated. Two sites appropriate for sampling with an 8 mm trephine were identified as being centered over the following points: (a) a point 7 mm caudal to the cranial dorsal spine and 7 mm ventral to the tuber sacrale, and (b) a point 7 mm caudal to the cranial ventral spine and 7 mm dorsal to the tuber coxae. Comparison of data obtained from males and females indicated that sampling variation may also be reduced by using dogs of one sex and by preferential use of males.