牙在牵引成骨区内移动的三维有限元分析

目的建立牙在下颌牵引成骨区内移动的三维有限元模型,比较在不同时间点上移动牙时牵引成骨区内应力的分布情况。方法利用多层螺旋CT扫描获得下颌骨及牙列的原始数据,采用CAD软件,建立三维有限元模型。在不同的骨愈合时期,模拟移动牙齿,利用Abqus软件对此模型进行三维有限元应力分析。结果建立了能模拟牙齿在下颌牵引成骨区内移动的三维有限元模型。在各个骨愈合的时期,成骨区对牙移动产生的应力反应没有显著差异,但在早期,牙齿将发生较大的倾斜。结论在牵引成骨完成后,早期移动牙齿时宜使用轻力。     

应用双向内置式牵引器矫正下颌骨短小畸形

目的:观察应用双向内置式下颌骨牵引器矫正下颌骨短小畸形结果.方法:下颌骨短小畸形2 例.在下颌角部位截骨,以下颌角为中心将双向内置式下颌骨牵引器上、下活动翼分别固定于升支和体部骨表面.术后第7 天开始牵引,各牵引螺杆的牵引速度为0.5~1.0 mm/d.待下颌骨升支高度和体部长度恢复较为理想后停止牵引,固定牵引装置3 个月. 结果:2 例患者均按计划完成牵引,无并发症.牵引升支和体部长度均为15 mm,下颌骨形态恢复理想.结论:双向内置式下颌骨牵引器可以在二维方向对下颌骨短小畸形的患者进行下颌骨形态重建,可以作为治疗不同类型下颌骨短小畸形的优选牵引装置之一.     

个体化内置式牵引器在修复下颌骨部分缺损中的应用

目的：应用个体化设计的内置式下颌骨牵引器,通过牵引成骨技术修复下颌骨部分缺损。方法：对因肿瘤行下颌骨部分切除的2例患者,术前根据头颅三维模型,设计个体化内置式牵引器,同期（1例）行肿瘤切除与牵引成骨手术,或二期1例行牵引成骨手术,运用转移盘牵引方式修复下颌骨部分缺损,固定期8～9个月,行X线及CT检查。结果：2例患者均成功进行了牵引器植入手术,术后牵引顺利,其中（1例）出现伤口感染,给予抗生素后得到控制,未影响牵引成骨治疗的进行。2例患者新骨形成均良好,转移盘远端骨质连接间隙处在拆除牵引器时需以植骨或钛板固定。结论：个体化设计的内置式下颌骨牵引器,可以根据不同患者颌骨缺损情况,进行一次性复杂牵引成骨,修复下颌骨部分缺损。     

口内入路个体化三焦点圆弧牵引器修复下颌骨大型缺损

目的:根据下颌骨缺损类型,设计个体化内置式圆弧牵引器,通过三焦点牵引成骨技术修复下颌骨缺损畸形。方法:对患成釉细胞瘤行下颌骨部分切除的患者,确定手术切除范围及修复后下颌骨形态,在快速原型模型上设计个体化内置式圆弧形牵引器,应用三焦点转移盘牵引方式,在肿瘤切除同期行牵引成骨手术,牵引前间歇期7d,牵引参数为0.4 mm/次,2次/d,固定期6个月。拆除牵引器后,二期行牙列修复。结果:牵引器植入后牵引过程顺利,固定6个月后X线片显示新骨形成均良好,但2个转移盘间见纤维愈合,拆除牵引器时需行钛板内固定。牙列修复前,发现下颌骨形态略小、矢状向后缩,再次行双侧下颌支矢状劈开前移下颌骨,到达设计位置并稳定后,行覆盖义齿修复。结论:个体化内置式圆弧牵引器可以有效修复下颌骨大型缺损,避免传统骨移植手术造成的供区创伤,但在前期设计时,需要适当矫枉过正。     

下颌骨体部牵张成骨的三维有限元研究

目的：用三维有限元法研究下颌骨体部不同牵张方向对下颌骨应力分布与位移的影响。方法：采用螺旋CT技术与计算机软件相结合,建立人下颌骨牵张成骨三维有限元模型。测量不同加载条件下,下颌骨的Mises应力、颏顶点和右侧下颌角点的位移。结果：建立了人下颌骨牵张成骨三维有限元模型。Mises应力集中在加载部位。双侧、与聒平面平行方向加载应力大,位移趋势为对侧前上方;单侧、与下颌骨下缘平行方向加载应力小,位移趋势为对侧后下方。单侧加载下颌骨向对侧偏斜多,双侧加载矢状向位移趋势大。结论：临床上应根据矫治需要,确定理想的牵张方向。     

下颌骨单侧骨皮质牵引的实验研究

目的 探讨下颌骨囊肿手术后遗留的单侧骨皮质缺损能否通过骨牵引延长技术而得到修复。方法 成年杂种犬6只，在下颌骨双尖牙区制备一个单皮质缺损区，安装牵引器，将其远中的骨皮质向骨缺损区牵引。结果 被移动颊侧骨板正常成活，牵引区成骨良好。结论 本实验的结果揭示了保持下颌骨连续性的单侧骨皮质牵引是可行的，牵引成骨表现与传统的全层离断的下颌骨延长的表现是相似的。     

牵张方向对下颌骨牵张成骨应力分布与位移影响的生物力学分析

目的 建立优化的下颌骨牵张成骨的三维有限元模型以研究下颌骨体部模拟牵张成骨时牵张方向对下颌骨体部牵张成骨的影响.方法 测量不同加载条件下,下颌骨的VonMises应力、位移.结果 可以看出当牵张器平行于下颌骨体放置时,模型中的最大应力是牵张器平行于矢状轴模型中最大应力的2倍.Von Mises应力集中主要发生在加载部位(牵张器与骨的结合点)和髁状突的颈部前下方区域,可能导致局部骨质吸收,从而造成螺钉松动,影响牵张器的稳固性.当模型的加载位移增加时,最大应力与加载位移值成线性关系.平行于下颌骨体组模型存在明显的侧方力,牵引装置牢固固定在下颌骨体部表面,牵引装置所产生的反作用力使它的后臂产生向外侧位移,这种装置-骨界面效应,可导致近中骨段颊侧移位,从而使牵张后的下颌骨形态发生变化,导致咬合关系错乱,面形改变,颞颌关节滑动轨迹的变化可能导致关节功能的紊乱.牵引装置平行于矢状轴放置时,这种反作用力可降至最低程度.结论 牵张器平行于矢状轴优于平行于下颌骨体,此项研究为牵张器在临床应用中的放置位置和牵引方向提供了理论依据.     

倾斜角度对种植体骨界面生物力学影响的三维有限元分析

目的 :分析不同倾斜种植对种植体界面应力、应变及位移分布状况的影响。方法 :在第一磨牙区分别垂直及向舌侧倾斜10°、20°、30°植入种植体 ,建立下颌骨三维有限元模型。模拟咀嚼肌力加载 ,分析在正中咬合情况下种植体骨界面应力、应变及位移分布情况。结果 :随着倾斜角度的增大 ,种植体骨界面应力、应变及位移均增加。倾斜30°种植时 ,种植体骨界面应力显著性增大(P<0.01)。结论 :种植体倾斜角度应小于30°。     

记忆合金牵引器弹力输出及对牵引成骨的影响

目的：了解记忆合金牵引器弹力输出特点，以及对牵引速度和新骨再生结果的影响。方法：设计不同记忆合金牵引器，生物力学检测仪测量绘制其弹力输出曲线，制作bi—focal牵引成骨重建一侧下颌骨3．5～4cm节段缺失的杂种犬动物模型，观察不同牵引器牵引成骨速度和长度。结果：记忆合金牵引器可输出稳定柔和的超弹性弹力，牵引速度超过传统的每天1mm，骨再生结果稳定，再生骨节段长度与牵引器外形设计和弹力强度相关。结论：记忆合金牵引器设计制作简便，弹力输出可控，可稳定成骨，具有深入研究价值。     

下颌骨牵引成骨对颞下颌关节的影响

利用牵引成骨技术扩张延长发育不良的下颌骨已获成功,近年来十分盛行。本文综述下颌骨牵引成骨过程对颞下颌关节影响的动物实验和临床应用研究,特别是下颌骨牵引成骨术对下颌骨发育不良病例的髁状突的影响,阐述应用传递牵引技术对重建髁状突切除术的髁状突和颞下颌关节的作用。     

牵张成骨延长犬下颌骨体缺损的有限元建模方法探讨

目的:探索快速建立牵张成骨延长犬下颌骨体缺损的有限元模型的方法。方法:对犬下颌骨进行多层螺旋CT扫描,运用M im ics软件读取基于实验犬下颌骨CT资料的D ICOM数据形成几何模型,在M agics软件中使用cut工具对几何模型进行切割、粘接,生成实体单元后在MARC软件中完成模型的力学分析。结果:首次建立了牵张成骨延长犬下颌骨体缺损的有限元模型,模型由五部分组成,可模拟牵张过程,观察任意点的应力、位移情况,并可选取模型的任意部分,查看其相应计算结果。结论:运用专业软件可以快速建立牵张成骨延长犬下颌骨体缺损的有限元模型。     

弧形牵张成骨重建人体下颌骨颏部节段性缺损的三维有限元研究

目的:建立下颌骨颏部节段性缺损弧形牵张成骨的三维有限元模型,研究弧形牵张成骨重建下颌骨颏部节断性缺损过程中,不断变化方向的牵张力对新骨组织形成的影响。方法:建立颏部节段性缺损的三维有限元模型,并把简化后的弧形牵张器有限元模型置入截断后的下颌骨,模拟弧形牵张成骨,并测量在弧形牵张成骨过程中下颌骨整体位移及其von Mises应力分布。结果:在未考虑唇颊侧软组织作用的前提下,弧形牵张成骨形成的新骨向舌侧生长,重建的下颌骨弧度较原下颌骨弧度变小。von Mises应力主要集中于牵张器在下颌骨的固位处。结论:在弧形牵张成骨重建下颌骨缺损过程中,牵张力本身就促使新骨组织向舌侧生长,从而使重建的下颌骨弧度较正常时小。此项研究为临床上如何克服弧形牵张成骨所形成的下颌骨弧度较小的不足,提供了一定的理论依据。     

有限元法探讨犬下颌不全截骨牵张的最佳截骨量

目的 利用不完全截骨牵张成骨重建犬下颌节段缺失的有限元模型,控制截骨程度,探讨最佳截骨量.方法 有限元模型模拟不完全截骨,在加力(12N)牵张过程中观察犬下颌皮质骨逐渐加大截骨量时截骨部位的Von Mises应力,并与犬下颌骨的极限抗拉强度比较,以获得牵引时不发生断裂(骨折)的最少剩余皮质骨量.结果 牵张过程中当连接处骨片剩余1mm时,滑动骨块和骨片的连接处Von Mises应力是47.76MPa,最接近犬下颌骨的极限抗拉强度(约49.35MPa).结论 犬下颌行半侧不全截骨牵张成骨时,当连接骨片的剩余宽度小于1mm时,将大大增加牵张区骨折的危险性.     

Biomechanical optimisation of the length ratio of the two endosseous portions in distraction implants: a three-dimensional finite element analysis

Insufficient alveolar height is one of the most common problems in oral implantation, and it may preclude placement of an implant or compromise the final aesthetic outcome of the restoration. To solve this problem, distraction implants (DIs) have been introduced because they can fulfill the functions of bony augmentation and implantation simultaneously and facilitate the operation, minimise the trauma, and shorten the duration of treatment. However, the high risk of complications such as device fracture from uneven distribution of stress or transport bone resorption from insufficient blood supply, has impeded their clinical use. As the cortical transport portion of the DI is more important for bearing occlusal force than the apical support portion, and the length of the transport portion is normally the height of the transport bone segment, lengthening the transport portion may help to obtain a rational distribution of stress and increase the blood supply to the transport bone. For those cases in which alveolar height is limited, the dimension of the DI must be minimised to be applicable, so it is important to find an optimised balance between the lengths of the transport and support portions for a better performance. We have made a finite element analysis to optimise the length ratio of transport:support portions. The effects of the length ratios on the stress distribution in the jawbones were evaluated. A ratio of 8:2 showed the minimum stress and most resistance to displacement. These results provide a valuable reference for further improvement of designs of DI and help to promote its clinical application.     

Biomechanical evaluation of sagittal maxillary internal distraction osteogenesis in unilateral cleft lip and palate patient and noncleft patients: A three-dimensional finite element analysis

Objective:To compare the pattern and amount of stress and displacement during maxillary sagittal distraction osteogenesis (DO) between a patient with unilateral cleft lip and palate (UCLP) and a noncleft patient.Materials and Methods:Three-dimensional finite element models for both skulls were constructed. Displacements of the surface landmarks and stress distributions in the circummaxillary sutures were analyzed after an anterior displacement of 6 mm was loaded to the elements where the inferior plates of the distractor were assumed to be fixed and were below the Le Fort I osteotomy line.Results:In sagittal plane, more forward movement was found on the noncleft side in the UCLP model (−6.401 mm on cleft side and −6.651 mm on noncleft side for the central incisor region). However, similar amounts of forward movement were seen in the control model. In the vertical plane, a clockwise rotation occurred in the UCLP model, whereas a counterclockwise rotation was seen in the control model. The mathematical UCLP model also showed higher stress values on the sutura nasomaxillaris, frontonasalis, and zygomatiomaxillaris on the cleft side than on the normal side.Conclusions:Not only did the sagittal distraction forces produce advancement forces at the intermaxillary sutures, but more stress was also present on the sutura nasomaxillaris, sutura frontonasalis, and sutura zygomaticomaxillaris on the cleft side than on the noncleft side.     

“颞下颌关节-下颌骨-颏兜矫形系统”三维正交各向异性有限元模型的建立

目的　在计算机上建立包括下颌骨、完整牙列、颏部软组织及颏兜的“颞下颌关节 (TMJ) -下颌骨 -颏兜矫形系统”三维正交各向异性有限元模型。方法　采用活体人颅标本、CT技术离散模型、SuperSAP(93)系统建模 ,采用缆索元、受压间隙元等形式进行边界约束。结果　建立了“TMJ-下颌骨 -颏兜矫形系统”三维正交各向异性有限元模型 ,包括下颌骨的硬组织、颏部软组织及颏兜矫治器 ,同时采用柔索性质的缆索元模拟咀嚼肌、韧带对下颌骨的约束 ,用受压间隙元模拟对牙合牙和关节凹的约束 ;建立的颏兜结构便于模拟临床加载。结论　建立的“TMJ-下颌骨 -颏兜矫形系统”三维正交各向异性有限元模型相似性好 ,为下颌骨受力的进一步研究奠定了基础     

Implant–Bone Interface Stress Distribution in Immediately Loaded Implants of Different Diameters: A Three-Dimensional Finite Element Analysis

Purpose: To establish a 3D finite element model of a mandible with dental implants for immediate loading and to analyze stress distribution in bone around implants of different diameters. Materials and Methods: Three mandible models, embedded with thread implants (ITI, Straumann, Switzerland) with diameters of 3.3, 4.1, and 4.8 mm, respectively, were developed using CT scanning and self‐developed Universal Surgical Integration System software. The von Mises stress and strain of the implant–bone interface were calculated with the ANSYS software when implants were loaded with 150 N vertical or buccolingual forces. Results: When the implants were loaded with vertical force, the von Mises stress concentrated on the mesial and distal surfaces of cortical bone around the neck of implants, with peak values of 25.0, 17.6 and 11.6 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains (5854, 4903, 4344 μ?) were located on the buccal cancellous bone around the implant bottom and threads of implants. The stress and strain were significantly lower (p < 0.05) with the increased diameter of implant. When the implants were loaded with buccolingual force, the peak von Mises stress values occurred on the buccal surface of cortical bone around the implant neck, with values of 131.1, 78.7, and 68.1 MPa for 3.3, 4.1, and 4.8 mm diameters, respectively, while the maximum strains occurred on the buccal surface of cancellous bone adjacent to the implant neck, with peak values of 14,218, 12,706, and 11,504 μm, respectively. The stress of the 4.1‐mm diameter implants was significantly lower (p < 0.05) than those of 3.3‐mm diameter implants, but not statistically different from that of the 4.8 mm implant. Conclusions: With an increase of implant diameter, stress and strain on the implant–bone interfaces significantly decreased, especially when the diameter increased from 3.3 to 4.1 mm. It appears that dental implants of 10 mm in length for immediate loading should be at least 4.1 mm in diameter, and uniaxial loading to dental implants should be avoided or minimized.     

Biomechanical and Finite Element Analysis of Mandibular Vertical Ramus Marginal Resection Designs

This study aims to know the post-surgical Von Mises stress of the mandible after two different vertical ramus marginal resection designs, analyze the results, compare with stress pattern of normal adult mandible without simulation and infer regarding the better of the two. Three groups of 3D finite element models of human adult mandibles were created. Group I (control)—normal mandible. Group II: Mandible with a quadrilateral vertical ramus marginal resection simulated. Group III: Mandible with an arc shaped vertical ramus marginal resection simulated. Finite element analysis (FEA) models were subjected to a point load of 475 N over right and left first molars, along with masticatory loads of masseter, medial pterygoid, anterior belly of digastric and temporalis loads in varying combinations (with and without bilateral temporalis and without right temporalis). The models were analyzed to infer the overall Von Mises stress in (a) the mandible (b) the sigmoid notch (c) postero-inferior resection corners. Results of our present study provides scientific evidence for the common practice of using arc form for marginal resection of vertical ramus of mandible whenever executed. Scientific evidence behind the concept of marginal resection of horizontal ramus is available but only scanty biomechanical evidence using finite element method (FEM) is available behind the same when performed in the vertical ramus, as magnitude and direction of loads in this region vary when compared to the horizontal ramus. The results ratify that incorporating arc shaped design pattern and removal of ipsilateral temporalis load by removal of coronoid, an area prone to stress concentration on loading, significantly decreases the post surgical Von Mises stress and hence would reduce the progressive micro-damage of the mandible after marginal resections of the vertical ramus of mandible.