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The purpose of this study was to investigate the relationship between the local elastic modulus and the internal structure of the compact bone of the mandibular bodies in human children. Small specimens of 6mm×0.4mm×0.9mm were obtained from the bone and the elastic modulus was measured by the three-point bending test. The surfaces of the specimen were observed serially by a scanning electron microscope and reconstructed three-dimensionally to clarify the correlation between the modulus and the internal bone structure. The porosity ratio was calculated based on the parameters obtained from the reconstructed test specimens. The local elastic modulus at the lingual side was higher than that at the labial side. At the buccal or labial side, the modulus of the lower margin of the mandibular body was higher than that of the alveolar part. However, there were no differences in the location of the specimens at the lingual side. The modulus of the deciduous molar region was greater than that of the incisor region. Relatively high values of the modulus were obvious with decreasing angles to the mandibular plane. The specimens with a high value of the modulus showed low porosity of bone. Specimens with a long axis consistent with the running direction of Haversian canals indicated a high value of the modulus. From these results, it is suggested that the location and difference of the local elastic modulus of the mandible may be related to the direction of the Haversian canals and the porosity of the bone. 抄録: 下顎骨の有限要素解析には,縦 弾性係数と骨の内部構造を詳細に把握する必要がある。本研究では,小 児下顎骨の微小試験片の三点曲げ試験により縦弾性係数を測定することを目的とし,走 査型電子顕微鏡を用いて その連続切片の三次元的観察を行い,縦 弾性係数と骨の内部構造との関係を調べた結果,以 下の結論を得た。小 児下顎体部の局所的な縦弾性係数は,測 定部位や方向により値が異なった。特に部位別では,唇 側と舌側の相対 する測定部位では舌側が大きな値を示した。方向別では,下 顎下縁平面に対する角度が小さくなると値は大きく 〒261-8502 千 葉 市 美 浜 区真 砂 1-2-2 時岡孝寛ほか:ヒ ト小児下顎骨体部の力学的特性に関する研究 283 な った。構築像 か ら求 めた骨 の空孔率 は,4.0-16.6%で あった。縦弾性 係数 と空 孔率 の相関 は,負 の相 関 がみ ら れ た。 同 じ空 孔率 を示す 試験片 で骨構 造 を観察 す る とハ ヴ ァー ス管の走 行が 異 なって いた。小 児下 顎骨 の局 所的 な縦 弾性 係数 の部位 差,異 方性 には,空 孔 率の違 い やハ ヴ ァー ス管の走 行方 向が大 き く関与 して い る ことが 示唆 された。

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Mechanical Properties of the Compact Bone of the Mandibular Bodies in Human Children. Relationship between the Local Elastic Modulus and the Histological Structure.