Bone resorption effected by denture use and osteporosis

本研究采用计算机x线摄影（CR）技术研制了骨密度测量系统，并应用该系统对无牙下颌骨骨密度分布进行了检测。研究结果如下：1。(1)准确度为4%（相对误差），重现性为1% （CV）。(2)将下颌骨分成小块的新方法可以在下颌骨的精确位置进行精确测量。无牙下颌骨骨密度分布舌侧和下缘骨密度由切牙区向磨牙区递减，而唇侧和颊侧骨密度增加。舌侧和下缘侧松质骨骨密度从切牙到前磨牙再到磨牙区下降。唇侧和颊侧骨密度无明显变化。前松质区下缘骨密度明显高于牙槽区（p< 0.01）。磨牙松质区颊侧骨密度显著高于舌侧骨密度（p< 0.01）。在松质骨和皮质骨中，髓舌骨脊的骨密度显著高于周围区域（p< 0.01）。发现了巨大的个体变异；在皮质区-颏孔附近和臼齿区牙槽嵴处，在松质区-前区舌缘和下缘处，在颏孔前6mm的唇侧。结果表明：(1)骨密度随肌肉附着部位和下颌管路径的变化而变化。(2)在前牙区颏孔和磨牙区颊松质骨之间深度放置固定物可以获得最佳的种植体稳定性。(3)磨牙区牙槽嵴骨密度可用于义齿状态变化的检测。(4)无牙下颌骨骨密度的三维分布可能有助于骨质疏松症的筛查。

This study developed bone mineral density (BMD) measuring system with computed radiography (CR) and examined BMD distribution in edentulous mandible with this system.The results are as followings :1. Measuring system for BMD using computed radiography(1) The accuracy was l.4% (relative error) and the reproducibility was l.l%(CV).(2) The new method that divides mandible into small portions allows the exact measurement at the precise position in the mandible.2. Distribution of BMD in edentulous mandibleBMI of cortical bone in lingual and inferior border side decreased from incisor to molar region, however, BMD in labial or buccal side increased.BMD of cancellous bone in lingual and inferior border side decreased from incisor to premolar to molar region.However BMD in labial and buccal side showed no changes.In anterior cancellous region, BMD in inferior border side significantly showed higher than in alveolar side (p<O.OO1).In molar cancellous region, BMD in buccal side was significantly higher than in lingual side(p<O.OO1). In cancellous and cortical bone, BMD at the mylohyoid ridge was significantly higher than the surrounding areas (p<O.OOl).The great individual varoination was found ; in cortical region-near mental foramen and at alveolar crest in molar region, in cancellous region-at the lingual and the inferior border in anterior region and at the labial side 6mm anterior to the mental foramen.The conclusions are as followings :(1) BMD seems to change in accordance with places of the muscle attachment and with the route of mandibular canal.(2) The stability of implants can be best obtained by deep placement of the fixture between the mental foramina in anterior region and placement into buccal cancellous bone in molar region.(3) BMD at alveolar crest in molar region may be useful for detecting changes from denture condition.(4) The 3-D distribution of BMD in edentulous mandible may be useful for osteoporosis screening.