Physical and chemical stimulations are major acquried environmental factors which influence the bone formation at growth stage. With three-week-old male rats of Wistar which simulate the weaning period of human being as subjects for study, the effect of intake of high protein diet on formation of bone in the mandible was investigated. The results were as follows : 1. Findings in bone density The control group showed significantly high values than calcium deficient diet group and calcium deficient high protein diet group (p<0.01). 2. Analytical findings of the X-ray microanalyzer In the quantative analyses of calcium and phosphorus, relative Ca ratio and relative P ratio showed decreasing values in the order of the control group, high protein diet group, calcium deficient diet group, and calcium deficient high protein diet group. 3. Histopathological findings As compared to the control group, the high protein diet group showed decreasing of the volume of bone matrix and accompanying decreasing of the number of bone lacunae. In spongious bone portion, osteoid tissue could be found partially. Decreasing of the bone lacunae, increasing of hypocalcification layer, and structureless areas could be found in calcium deficient high protein diet group as compared to the calcium deficient diet group. The foregoing findings showed that excessive protein intake inhibited bone formation in the mandible at growth stage, regardless of the presnce or absence of calcium.
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