目的探讨在不同力作用下,长度和直径同时连续变化情况下微种植体尺寸的优化设计,以期为临床上合理选择微种植体尺寸提供理论基础。方法建立长度和直径连续变化的微种植体及周围颌骨组织的三维有限元模型,设定长度变化范围为6~12 mm,直径变化范围为1.2~2.0 mm,在微种植体头部的横槽内分别加载水平力(HF)和复合力(CF),观察长度和直径同时变化对周围颌骨等效应力峰值(Max EQV)及微种植体位移峰值(Max DM)的影响。结果在两种力的作用下,随着长度和直径的增加,颌骨Max EQV和微种植体Max DM均下降,当长度大于9 mm时,各评估指标值较小且变化幅度较小。灵敏度分析显示,直径对评估指标的影响较大。在CF作用下,直径对评估指标的影响较HF作用下显著。结论在本研究所设定的参数范围内,微种植体的长度应不超过9 mm,运用微种植体对牙齿进行转矩控制时,其直径应超过1.2 mm。

Objective To investigate the effect of different length and diameters on the stability of mini implant and to select optimal length and diameter using continuous variation of parameters. Methods To perform 3-dimensional finite element analysis, finite element models of a maxilla, and mini implants with length of 6-12 mm and diameters of 1.2-2.0 mm were generated. Load of two different forces were applied to the head of mini implant. One type was horizontal force (HF), the other was composite force (CF). The maximum equivalent stress (Max EQV) in maxilla and the maximum displacement (Max DM) of mini implant were evaluated. Results The Max EQV in maxilla and Max DM of mini implant decreased as length and diameter increased. When length was more than 9 mm, the evaluation indexes were small and had a less change. Datas indicated that diameter played a more important role in reducing target, and was a more effective parameter in re-ducing Max EQV when CF was loaded. Conclusion From biomecha

目的探讨不同长度的眶部种植体对骨界面应力分布的影响。方法建立直径3.75 mm,长度分别为3、4、6、10 mm的眶部种植体—颅颌面骨三维有限元模型,分别给予沿种植体轴向和与轴向成45°的载荷,载荷大小20 N,记录两种方向载荷下种植体及骨界面的Von-Mises应力峰值和位移峰值,分析其应力分布。结果施加沿种植体轴向载荷时,种植体周围应力集中于根部,种植体受力大于骨面;施加与轴向成45°载荷时,应力集中于种植体颈部与第一螺纹之间,种植体受力大于骨面。施加两个方向的载荷时,3 mm种植体的应力峰值明显大于其他长度种植体,而位移峰值无明显变化。在相同长度下,施加沿种植体轴向载荷时的应力峰值及位移峰值均明显低于与轴向成45°载荷时,载荷方式对界面应力分布有明显的影响。结论临床上尽量选择4 mm以上的眶部种植体;应用3 mm种植体时,应选择骨密质较厚的区域植入。

Objective This study aims to observe the effect of orbital implant lengths on stress distribution in peri-implant surfaces. Methods The three-dimensional finite element analysis models of craniofacial and orbital implants with a diameter of 3.75 mm and lengths of 3, 4, 6, and 10 mm were established. A force of 20 N was applied to the models. The stress and displacement distribution under every condition were recorded and analyzed. Results The loading direction along the implant axis and the stress concentration on the implant root were observed. The loading direction was at a 45 degree angle relative to the implant axis, and the stress concentration was located at the implant neck and the first screw thread. The maximum stress of the 3 mm implant was significantly higher than that under the other two loading directions. The maximum displace-ment of the four lengths exhibited no significant change. Given the same implant length, stress, and displacement, the peak of the implan

目的应用三维有限元法分析动态加载下种植体植入位置和直径对悬臂梁种植固定义齿应力的影响。方法建立左下颌第二前磨牙、第一磨牙、第二磨牙缺失种植固定义齿的三维有限元模型,远中种植体的位置和直径保持不变;近中种植体依次向远中移动形成中轴与第一前磨牙远中面距离D分别为5.5、8.0、10.5、13.0 mm的悬臂梁种植固定义齿,分别采用4.1和4.8 mm两种直径的种植体;以250 N力模拟咀嚼周期0.875 s的动态载荷加载于颊尖和舌尖上,应用有限元分析软件MSC.Marc和Partran分析种植体—骨组织界面的Von Mises应力情况。结果随着近中种植体逐渐向远中移动,近远中种植体Von Mises应力均有不同程度增高,近中种植体中轴与第一前磨牙远中面距离D≤8.0 mm范围内种植体最大Von Mises应力增幅缓和,D8.0 mm时应力急剧加大;近中种植体直径增大,则近远中种植体的应力减小;各加载阶段最大Von Mises应力均处于近远中种植体颈部与皮质骨交界处;斜向加载种植体应力显著大于垂直加载。结论种植体植入位置是影响悬臂梁种植固定义齿应力的重要因素,悬臂梁长度不超过前磨牙宽度时行种植固定义齿设计是可行的,直径的选择要考虑骨量和悬臂梁长度双重因素。

Objective To examine the effect of the location and diameter of implants on stress distribution in three-unit implant-supported posterior cantilever fixed partial dentures (FPD) in the mandible. Methods A three-dimensional finite element model was developed to represent a rigid implant-supported posterior FPD that restores the second left premolar, first molar, and second molar. The location of the distal implant with a diameter of 4.8 mm remained the same, whereas the mesial implants with diameters of 4.1 and 4.8 mm were successively moved toward the posterior area with distances of 5.5, 8.0, 10.5, and 13.0 mm from the long axis of the mesial implants to the first premolar to form the cantilever FPD. Dynamic loads of 250 N were applied from different directions on the buccal and lingual cusps of the FPD to simulate the masticatory cycle for 0.875 s. The maximum Von Mises stresses were calculated using the finite element analysis software MSC. Marc and Partran. Results The maximum Von

目的：利用有限元法探讨上颌牙列缺失应用 All-on-4修复时种植体在3种牙弓形态模型中应力分布的差异，为临床提高种植体成功率提供客观参数。方法：参照3M公司 MBTTM牙弓模板，应用 SolidWorks 2013软件建立 All-on-4种植修复的3种牙弓形态上颌无牙颌有限元模型（尖圆形、方圆形和卵圆形），设定皮质骨层为2 mm，种植体长度为13 mm，前牙区2颗种植体平行植入，后牙区2颗种植体在颌骨内沿近远中方向与牙长轴成0°、15°、30°和45°4种角度，所有种植体均固定于上部结构。通过2种加载方式在上部结构施加100 N压力模拟咀嚼受力，应用有限元软件Abaqus 6.13运算测得种植体在上颌模型的Von-Mises应力值。结果：测得种植体周围 Max von-Mises应力值均出现在皮质骨层，不同牙弓形态模型中应力分布不同，方圆形牙弓种植体周围应力随种植体角度增加而增大；卵圆形牙弓后牙区最大应力值出现在种植体倾斜15°时，前牙区应力在种植体倾斜超过15°后明显提高；尖圆形牙弓种植体周围应力在种植体倾斜45°时显著增大。结论：牙弓形态对种植体周围应力分布有显著影响，All-on-4修复上颌牙列缺失时，方圆形牙弓应尽量减少种植倾斜体角度，卵圆形牙弓种植体倾斜角度不宜超过15°，尖圆

Objective To explore the effect of different arch forms of maxillary models on stress distribution of peri-implant of All-on-4 implants with 3-dimensional finite element, and to provide evidence for the improvement of implant achievement ratio in clinic. Methods 3-dimensional finite element analysis models of Tapered,Square and Ovoid arch form maxillary based on the MBTTM Arch Form Templates were constructed by using Solidworks software.The cortical bone thickness was defined as 2 mm at all points.The implants with 13 mm in length were inserted between the mental foramina.The 2 posterior implants were set at 4 inclination angle,from 0°to 45°.All implants were splinted with superstructure.A 100 N pressure was applied to 2 kinds of loading positions on the superstructure models. The maximum Von-Mises stress on cortical bone around the implants was measured by using Abaqus software.Results The maximum Von-Mises value in maxillary cortical bone with All-on-4 implants in 3 arch

采用大田种植方法,以郑单958为试验材料,于玉米7展叶期(E7)、9展叶期(E9)喷施乙烯利,比较研究玉米产量、果穗维管束特征、子粒干物质积累及相关生理指标,探讨乙烯利对玉米果穗发育的影响及生理机制。结果表明,乙烯利处理使玉米子粒千粒重下降;子粒灌浆起始生长势降低、灌浆天数缩短,可溶性淀粉积累量下降;子粒中IAA(生长素)含量降低、ABA(脱落酸)含量升高,果穗穗轴的维管束长度及筛管半径显著降低,穗柄维管束个数下降、维管束长度也下降。IAA含量下降抑制木质素前体苯丙烷及木质素的形成,进而抑制木质部的形成,使得维管束个数、长度下降,进而子粒库容降低,子粒库活性降低,导致最终产量下降。

The field cultivation was used as the main research method by taking hybrids Zhengdan 958 of mate-rials. In order to investigate effects of Ethephon on the dry matter accumulation of summer maize seeds and inquire related physiological mechanism, the changes of yield, vascular bundle characteristics, accumulation of dry matter of grain, changes of soluble sugar and starch grain hormone in root bleeding volume and changes of inorganic ion content and hormone content were compared by spraying ethephon in the seventh and ninth expansion leaf period maize.The results showed that under ethephon treatment, seed grain thousand weight and volume, grain storage and soluble starch accumulation in grain declined, grain-filling starting growth potential of Zhengdan 958 reduced, grout-ing days were shorten. Grain was with lower IAA content but higher ABA content. Spraying ethephon significantly reduced the length of the ear cob of vascular bundle and the radius of screen in the process of