骨支持式手术辅助上颌骨快速扩弓位移分布的三维有限元分析

Displacement distribution analysis of surgically assisted bone-borne rapid maxillary expansion

目的:研究骨支持式手术辅助上颌骨快速扩弓中颅面部各解剖部位的位移情况。方法:建立骨支持式手术辅助上颌骨快速扩弓系统的三维有限元模型,手术方式采用腭中缝联合侧方皮质骨切开术,模型上选取24个解剖结构,加载横向7mm扩弓量,比较分析颅面部各个解剖部位在矢状向、横向、垂直向的位移分布情况。结果:矢状向观,上颌骨各解剖结构都有明显的向前位移的趋势,而面上部解剖结构都有向后移位的趋势。横向正面观,颅上颌复合体呈金字塔样打开,鼻腔底部明显扩大约4.5mm;面观,支抗牙的牙根位移(第一前磨牙为2.92mm,第一磨牙为3.26mm)小于相应区域颊侧牙槽骨的位移(第一前磨牙区3.76mm,第一磨牙区3.93mm),腭板前部比后部扩开更大。垂直向观,上颌骨正中区的腭板有向下位移的趋势,颅面部其余解剖部位都向上移动。结论:骨支持式手术辅助上颌骨快速扩弓时,上颌骨在三维方向上有不同程度的移动、旋转和侧方倾斜,利用这些变化,可以辅助矫正轻度颅颌面畸形。骨支持式扩弓器将扩弓力直接传导到骨骼上,因此可以很好地避免牙支持式扩弓器扩弓时引起的牙及其周围支持组织损伤等严重并发症。

PURPOSE： The aim of this study was to investigate the displacement distribution of the various anatomic structures of the eraniofacial complex during surgically assisted bone-borne rapid maxillary expansion （SARME）. METHODS： Three-dimensional finite element model of craniofaeial complex with a bone-borne appliance was generated. The surgical technique was the combination of midline osteotomy and lateral corticotomy. Displacements were measured at 24 anatomical structures of the craniofacial complex when 7ram transverse expansion was executed.Displacements distribution of various structures in sagittal, transversal and vertical directions were then analysed and compared. RESULTS： In sagittal plane, various structures representative of the maxilla presented forward displacement ,whereas structures of the upper face had a tendency to move backward. In transversal plane, pyramidal displacement of maxilla away from the midline was evident from the frontal view. Lateral walls of the nasal cavity separated more widely, approximately to 4.5mm. Viewed occlusally, the displacement of roots of the first premolar （2.92mm） and first molar （3.26mm） was smaller than that of the buecal dento-alveolar （the first premolar region was 3.76mm and first molar region was 3.93mm）. The anterior part of the palatal plate expanded widely than the posterior part. In vertical plane, palatal plate typical of the medial parts of the maxilla indicated downward displacement while the remaining structures of the craniofacial complex displaced upward. CONCLUSION： During surgically assisted bone-borne rapid maxillary expansion （SARME）, the maxilla showed displacement, tipping and lateral rotation in three dimension. These changes may facilitate to correct mild eraniofacial deformities. The bone-borne appliance made it possible to transfer expansion forces directly to the bone. As a result ,this could avoid the trauma of anchorage teeth and their periodontal tissues usually caused by the use of tooth-appliance.