不同重建工况下Forsus前导下颌后髁突应力、位移的分布变化

Stress and displacement distribution of mandibular condyle advanced with Forsus under different occlusal reconstruction conditions

目的仿真分析不同工况下推杆式矫治器(Forsus)前导下颌后髁突应力、位移的分布变化,为Forsus临床应用提供参考。方法经Abaqus6.5软件构建Forsus前导下颌三维有限元模型,模拟下颌水平前伸距离分别为3、4、5、6、7 mm,对应下颌垂直打开距离为4、3.5、3、2.5、2 mm的5种重建工况,分析"下颌骨-颞下颌关节"的应力、位移变化和旋转趋势,以评估髁突生长改建的重建方式。结果 5种工况下,最大应力分布在下颌骨髁突、乙状切迹区和髁突颈后份区域。随下颌水平前导的位移量增加,髁突乙状切迹区和髁突颈后份区域应力较缓增大,但仍处于相同数量级(30 MPa);髁突区域应力分布较稳定且没有明显的应力集中。从工况1～5髁突水平方向位移逐渐增大,方向皆向前;髁突垂直向位移平均值也逐渐增大,方向皆向下;下颌骨直接拉伸到指定重建位置时,髁突运动方向也为前下。结论生理性咬合重建的范围,不同程度地前导下颌不会改变髁突软骨附近的应力分布趋势。考虑颞下颌关节生理承受性,严重下颌后缩时可分段前伸以利于髁突生长改建。

Objective To analyze changes of stress and displacement distribution of the mandibular condyle under different occlusal reconstruction conditions by using the Forsus,and to provide clinical reference for the applica-tion of the Forsus.Method The software Abaqus6.5 was employed to build the 3D finite element model of man-dibular condyle for simulation.Under different occlusal reconstruction conditions,the distances of mandibular pro-traction were 3 mm,4 mm,5 mm,6 mm and 7 mm and the mandibular＇s opening distances were got as 4 mm,3.5 mm,3 mm,2.5 mm and 2 mm correspondingly.The stress,displacement and rotation trends of mandibula-temporomandibular articulation were analyzed and the estimation of occlusal reconstruction contributing to the growth of the condyle was made.Results The 3D model showed that the maximum stress distributed on the mandibular condyloid process,sigmoid incisure of mandible and the posterior neck of condyle area under the five different conditions.With the increase of displacement in mandibular condyle,the stress increased slowly on the sigmoid incisure of mandible and the posterior neck of condyle area,but the stress still kept in the same order ofmagnitude（30 MPa）.The stress distribution of mandibular condyloid process was in a steady state with no obvi-ous stress concentration.The displacement of condyle in horizontal direction increased gradually and forward,and the displacement of condyle in vertical direction also increased gradually but downward.When the mandibular was stretched to the designed reconstructive location,the condyle moved downward.Conclusions The range of physiological occlusal reconstruction will not change the stress distribution trends of the condylar cartilage,even when the mandibular moves forwards in varying degrees.Considering the physiological nature of temporomandib-ular articulation and the growth of the condyle,when the mandibular retrusion is severe,it would be advisable by subsection protrusion.