Bone resorption effected by denture use and osteporosis

本研究利用计算机X线摄影（CR）技术研制了骨密度（BMD）测量系统，并利用该系统对无牙颌下颌骨BMD分布进行了研究。计算机X线骨密度测量系统（1）准确度为1.4%（相对误差），重复性为1.1%（CV）。(2)这种将下颌骨分割成小块的新方法可以在下颌骨的精确位置进行精确测量.无牙颌下颌骨骨密度分布舌侧和下缘皮质骨BMI从切牙区到磨牙区逐渐降低，唇侧和颊侧BMD逐渐升高;舌侧和下缘松质骨BMD从切牙区到前磨牙区再到磨牙区逐渐降低，唇侧和颊侧BMD无明显变化;前松质骨区，下颌骨下缘骨密度显著高于牙槽骨（p<0.001），磨牙松质骨区颊侧骨密度显著高于舌侧（p<0.001）。在松质骨和皮质骨中，下颌舌骨嵴处的BMD显著高于周围区域在皮质区-颏孔附近、磨牙区牙槽嵴、松质骨区-前区舌下缘、颏孔前6 mm唇侧，均有较大的个体内翻。（1）骨密度随肌附着部位和下颌管走行方向的变化而变化。(2)前牙区颏孔间及磨牙区颊侧松质骨内植入固定器，可获得最佳的种植体稳定性。(3)磨牙区牙槽嵴骨密度可用于检测义齿条件的变化。(4)无牙颌骨密度的三维分布可用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.