Reversibility of Nutritional Osteoporosis: Physicochemical Data on Bones from an Experimental Study in Dogs

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Abstract
The reversibility of nutritional osteoporosis was studied in adult dogs. Ten beagles were fed a depletion diet (low Ca-high P) for 42 weeks after which time three dogs were necropsied and the remaining seven dogs were placed on a repletion diet (high Ca-balanced P) for up to 28 weeks. Mobility of incisor teeth occurred in all dogs at the end of depletion. It decreased rapidly on repletion diet and disappeared within 12 weeks. Intravital radiograms before and after depletion showed pronounced loss of interradicular bone in the mandibular molar area. Macroradiography of mandibles at necropsy revealed reappearance of bone within 4 weeks and apparent return to normalcy after 28 weeks on repletion diet. Enlarged Haversian and Volkmann's canals and numerous soft osteons present in microradiograms of long bones at the end of depletion became fewer with repletion. Densitometry of mandibles showed that remineralization was a linear function of time on repletion and that restitution had occurred within 24 weeks. Specific gravity and ash content determinations showed that bone loss was more severe in vertebrae than in long bones at end of depletion and that reversal was faster in vertebrae than in long bones on repletion diet. Bending and tension tests of cortical bone indicated that the biomechanical quality improved with time on repletion diet. The implications of the results on human osteoporosis are discussed.