三种螺距对种植体初期稳定性影响的有限元研究

目的：利用即刻负载有限元模型,研究种植体不同螺纹螺距因素对初期稳定性的影响。方法：利用Pro／E软件、Hypermesh软件及ABAQUS有限元软件,建立四类种植体即刻负载的三维有限元模型,比较3种螺纹螺距（0．8mm、1．6mm、2．4mm）在分别垂直和水平加载时,对种植体初期稳定性的影响。结果：对不同螺纹螺距种植体来说,垂直加载和水平加载时0．8mm螺距螺纹种植体微动最小,2．4mm螺距螺纹种植体微动最大。结论：螺纹的螺距对垂直相对位移有影响,对水平相对位移影响不大。随着螺距的增加,种植体对抗垂直向载荷的抵抗力减弱。水平加载时,螺纹的螺距对颈部微动影响不明显。     

螺纹形态和螺距对种植体系统应力影响的三维有限元研究

目的研究根据标准螺纹参数设计的不同螺纹形态和螺距的9种牙种植体受载后牙槽骨及整个种植系统的应力变化,为种植体系统的优化设计及临床应用提供理论依据。方法采用Solidworks软件建立了螺纹形态分别为V形、梯形、锯齿形,螺距分别为0.7 mm、0.8 mm、1.0 mm的9种标准螺纹式种植体模型,配以基台、基台螺丝构成整套种植体系统,根据CT扫描数据重建下颌骨模型,在垂直向和与种植体长轴成15°斜向分别加载100 N力,ANSYS有限元分析软件计算比较种植体系统和周围牙槽骨的应力及位移分布状况。结果综合考虑种植体系统各部件和种植体周围牙槽骨所受应力,9种种植体中,螺纹形态为V形、螺距为0.8 mm的种植体在垂直向和斜向加载时应力较小。9种种植体各部件及周围牙槽骨最大位移量垂直向加载时为2.61μm,斜向加载时为23.78μm,9种种植体的位移差异小。结论螺纹形态为V形、螺距为0.8 mm的种植体力学性能较好。螺纹形态和螺距对种植体系统及周围牙槽骨的位移影响不大。     

单、双、三螺纹种植体初期稳定性的三维有限元比较研究

目的:使用三维有限元的方法分析单、双、三螺纹种植体即刻负载时的稳定性的情况,对这3种螺纹进行综合评价。方法:利用Pro/E软件、Hypermesh软件及ABAQUS有限元软件,建立3类种植体即刻负载的三维有限元模型,比较3种螺纹在分别垂直和水平加载时对种植体初期稳定性的影响。结果:3种螺纹形态中,单螺纹的垂直相对位移和综合相对位移最小,三螺纹最大。结论:随着种植体旋转角度的增加,其对抗垂直载荷的抵抗力减弱。     

支抗种植体外形对骨界面应力分布的影响

目的：探讨三种圆柱状支抗种植体外形差异对骨界面应力分布的影响，以筛选最佳支抗种植体。方法：用三维有限元方法给种植体施加150g近远中方向的载荷，分别对刃状螺纹型、矩形螺纹型及光滑型支抗种植体-骨界面进行应力和位移分析。结果：三种种植体颈部的Von-Mises应力值分别为0．5330MPa、1．1600MPa、0．8900MPa；位移分别为0．1630μm、0．1690μm、0．1460μm。结论：刃状螺纹种植体做支抗时，其颈部应力值最低，而三种种植体颈部的齿槽骨位移差异不显著，敌刃状螺纹型种植体比较适合做支抗种植体。     

不同螺距种植体集中载荷的有限元分析

目的:用三维有限元方法分析不同螺距种植体-骨界面应力分布状况,确定利于应力均匀分布的最佳螺纹参数设计.方法:建立包含上部结构的牙种植体、局部下颌骨块三维有限元模型,利用Cosmos/works软件分析在垂直、斜向45° 2 种集中载荷下螺距分别为0.6、 0.8、 1.0 mm的3 种种植体与骨界面的应力分布状况.结果:螺距为0.8 mm种植体周围Von-Mises应力、拉应力、压应力峰值较小,应力分布最均匀;同一螺距种植体斜向载荷下应力显著高于垂直载荷;应力集中主要出现于种植体颈部、皮质骨上缘和种植体末端最下一个螺纹处.结论:螺纹种植体螺距影响骨界面的应力分布和(牙合)力传导,为避免应力集中种植体末端螺纹应进行适当的截齿处理,种植义齿设计和修复时应尽可能减小或避免非轴向力.     

螺距对即刻负载种植体和周围骨组织影响的三维有限元研究

目的探讨在即刻种植负载条件下,种植体形成骨结合后,梯形螺纹螺距对种植体和周围骨组织的影响,为种植体结构的优化提供依据。方法运用计算机辅助设计j维建模软件Solidworks,建立螺距分别为0．6mm、0．7mm、0．8mm、1．0mm、1．2mm、1．3mm、1．4mm、1．6mm的圆柱状梯形螺纹种植体模型,再将其分别与利用CT扫描数据蓖建的下颌骨组织模型进行仿真结合,在即刻加载情况下且种植体形成骨结合后,分别施加垂直向和与种植体长轴成15°的颊舌向力150N。运用ANSYSWorkbench有限元分析软件进行模拟仿真分析,比较种植体和周围牙槽骨组织,随种植体螺距改变而引起的应力、应变的变化。结果即刻负载且种植体与骨结合完成后,垂直向加载,皮质骨在种植体螺距为0．8mm和1．0mm时,Von—Mise应力、应变均较小;松质骨在螺距为0．7mm、0．8mm、1．0mm时,Von—Mise应力、应变较小;种植体在螺距为1．6mm时应力最小为44．18MPa,螺距为0．8mm时应变最小为11．04μm。颊舌向加载,皮质骨在螺距为0．7mm、0．8mm时,Von-Mise应力、应变较小;松质骨在螺距为0．6mm、0．7mm、0．8mm时,Von—Mise应力、应变均较小;种植体在螺距为0．8mm时应力最小为188．23MPa,螺距为0．6mm时应变最小为23．69μm。结论对于圆柱状梯形螺纹种植体,螺距选取1．0mm、1．2mm、1．3mm或1．4mm时,在即刻负载情况下,当种植体与骨结合完成后,种植体-骨组织系统各主要零件的综合力学性能较好、形变较小,对骨的破坏小,有利于种植稳定性的提高。     

螺纹种植体螺距的优化设计和应力分析

目的应用Ansys Workbench DesignXplorer优化设计模块,探讨圆柱状V形螺纹种植体螺距变化对颌骨和
种植体应力大小的影响,为临床设计和选择最佳的螺纹参数提供理论依据。方法建立了包含圆柱状V形螺纹种植
体的颌骨骨块三维有限元模型,设定螺纹螺距（ P）范围为0.5～1.6 mm,观察P变化对颌骨和种植体Equivale（nt EQV）
应力峰值的影响。结果在垂直向加载中皮质骨、松质骨和种植体的EQV应力峰值增幅分别为7.1%、123.4%和
28.7%;在颊舌向加载中皮质骨、松质骨和种植体的EQV增幅分别为2.8%、28.8%和14.9%;在各种加载情况下,当
变量P大于0.8 mm时,对颌骨及种植体的EQV应力峰值响应曲线曲率位于- 1和1之间。结论松质骨的应力大小更
易受到螺距的影响;螺纹对垂直加载时的力学传递影响更明显;螺距在保护种植体垂直受力时起着更为重要的作
用;圆柱状螺纹种植体螺距最佳设计应不小于0.8 mm,但同时应避免过大的螺距。     

支抗种植体长度对骨界面应力分布的影响

目的：研究不同长度支抗种植体对骨界面应力分布的影响，以供临床筛选合适的种植体。方法：用三维有限元方法给种植体施加150g近远中方向的载荷，分别对长度为7mm、10mm、15mm的支抗种植体-骨界面进行应力分析。结果：三种长度种植体颈部的Von-Mises应力值分别为0．5450MPa、0．5330MPa、0．5320MPa；位移值分别为0．1690μm、0．1630μm、0．1610μm。结论：在种植体承受侧向力载荷时，增加种植体长度可提高其承载能力，临床上在选择正畸支抗种植体时，应尽量选择长种植体作正畸支抗体。     

皮质骨厚度对支抗种植体-骨界面应力分布的影响

目的：研究皮质骨厚度改变对支抗种植体-骨界面应力分布的影响，供临床参考。方法：用三维有限元方法，对分别种植于皮质骨厚度为0．5mm、1．0mm、2．0mm颌骨模型中的种植体施加150g近远中方向的载荷，分析支抗种植体-骨界面应力分布情况：结果：三者种植体颈部的Von-Mises应力值分别为0．6040MPa、0．5330MPa、0．5380MPa；位移值分别为0．2110μm、0．1630μm、0．1250μm：结论：皮质骨在一定厚度内，植入体颈部皮质骨越薄，骨界面应力值就越大：但皮质骨超过一定厚度后，骨界面应力并不随其厚度的增加而做相应递减。皮质骨的厚度与界面骨的位移成反比.     

支抗种植体不同螺纹顶角对骨界面应力分布的影响

目的 研究刃状螺纹型支抗种植体的螺纹顶角改变对骨界面应力分布的影响,以供临床筛选合适的支抗种植体。方法 用三维有限元方法给种植体施加150g近远中方向的载荷,分别对螺纹顶角为60°、75°、120°的三种支抗种植体-骨界面进行应力分析。结果 三种螺纹顶角种植体颈部的Von-Mises应力值分别为0.533 0 MPa、0.632 0 Mpa、0.591 0 Mpa;位移值分别为0.1630μm、0.1590μm、0.1520μm。结论 螺纹顶角为60°的种植体适合作正畸支抗体。     

Biomechanical analysis of alveolar bone stress around implants with different thread designs and pitches in the mandibular molar area

Threaded implants have been shown to play an important role in increasing mechanical osseointegration. The aim of this study was to determine bone stress distribution when using different types of implant thread pitches and designs. Five 3D finite element models were constructed to simulate bone stresses induced in implant bodies with two types of thread form: triangular (“Tri” prefix) and trapezoidal (“Trap” prefix). The former had thread pitches of 0.8, 1.2, and 1.6 mm, while the latter had thread pitches of 1.2 and 1.6 mm. A biting load of 143 N was applied vertically and obliquely to the occlusal central fossa of the crown. The main effects of each level of the three factors investigated (loading type, pitch, and thread form) in terms of the stress value were computed for all models. Results indicated that the loading type was the main factor of influence on the peak compressive stress of the alveolar bone. Optimal thread pitch was 1.2 mm for a triangular-thread implant, and a trapezoidal-threaded implant with thread pitch of 1.6 mm had the lowest stress value among trapezoidal-threaded implants. This study concluded that each thread form has its unique optimal thread pitch with regard to lower concentration of bone stress. Clinically, this study suggests that in biomechanical consideration, thread pitch exceeding 0.8 mm is more appropriate for a screwed implant. For clinical cases that require greater bone-implant interface, trapezoidal-threaded implants with thread pitch of 1.6 mm provide greater primary stability and lower concentration of bone stress under different loading directions.     

The influence of implant design on bone remodeling around surface-modified Southern Implants®

Background: Implant survival and success have shown to be related to a number of factors. Aim: To evaluate the impact of implant design on implant survival and success, focusing on thread pitch and implant shape. Materials and Methods: Non‐smoking patients treated by two experienced periodontists with standard diameter externally‐hexed Southern® implant(s) inserted in healed bone were retrospectively selected. A one‐stage surgical approach was used in all cases and implants had been installed for at least 6 months. Information pertaining to patient‐related variables, time of loading, implant design and radiographical outcome was retrieved from patients' records. Implant success was defined according to the criteria by Albrektsson and Isidor, taking into consideration bone level, defined as the distance from the implant–abutment interface to the first bone‐to‐implant contact. Results: In total, 59 patients treated with one hundred eleven externally‐hexed Southern Implants® met the inclusion criteria. Fifty‐six straight implants with a thread pitch of 0.6 mm and 55 tapered implants with a thread pitch of 1.0 mm were placed. The total implant survival rate was 98.2% after a mean follow‐up period of 14 months (range 6–28). The mean bone level was 1.35 mm (SD 0.46, range 0.59–3.70) and the overall implant success rate was 75.7%. Age, gender, length, and time of loading were not decisive for implant neither failure nor bone loss in contradiction to implant design and thread pitch (p < .01). Tapered implants with a 1.0 mm thread pitch were less successful than parallel‐walled implants with a 0.6 mm thread pitch. Conclusion: The Southern Implants® system shows good short‐term survival rates and bone preservation. However, bone remodeling seems affected by the implant design. Whether this is due to the tapered shape of the implant or the thread pitch is unclear and needs to be elucidated in future research.     

Effect of dental implant cross-sectional design on cortical bone structure using finite element analysis

Purpose: This finite element analysis investigation evaluated the effect of different implant cross‐sectional designs on bone stress levels under different loading patterns. Materials and Methods: Finite element analysis program was used to construct four different three‐dimensional models describing 4 × 10‐mm implants in blocks of cortical and trabecular bone. A 5‐mm‐long abutment was modeled above each implant. The implant in model 1 was unthreaded, while in model 2 the implant was circularly threaded. The third implant in model 3 had the cross‐sectional shape as a 16‐sided star‐shaped design. The implant in model 4 was constructed unthreaded, with a diameter of 4.5 mm. Vertical and horizontal loads of 100 N each were applied on the top middle node of each implant assembly. All nodes at the bottom surface of the bone models were restrained. Results: By comparing models 1, 2, and 3, the lowest bone stress values under vertical and horizontal forces were observed around the unthreaded implant in model 1 (8.92 and 94.52 MPa, respectively). The highest stress value under vertical loading was shown around the threaded implant in model 2 (10.07 MPa), whereas the highest stress value under horizontal loading was observed around the star‐shaped implant in model 3 (108.40 MPa). Model 4, with a wider unthreaded design, had stress values under vertical and horizontal loading of 7.32 and 71.35 MPa, respectively. Conclusions: It was concluded that the unthreaded implant design produced the least bone stress. An increase in implant diameter could produce marked reduction in stress value in the bone around the neck of the implant.     

种植牙即刻负重的生物力学的三维有限元分析

目的 用三维有限元的方法分析牙种植体不同角度即刻负重的骨界面应力分布规律.方法 选成人无牙下颌骨进行薄层螺旋CT扫描,将扫描图像导入通用外科手术集成系统,建立下颌骨三维网格模型.模拟标准的螺纹实心种植体,建立种植体一下颌骨即刻负重的三维有限元模型.以150 N的力轴向加载和分别10.、20.、30.侧向加载,应用ANS...     

The effect of thread pattern upon implant osseointegration

Objectives: Implant design features such as macro‐ and micro‐design may influence overall implant success. Limited information is currently available. Therefore, it is the purpose of this paper to examine these factors such as thread pitch, thread geometry, helix angle, thread depth and width as well as implant crestal module may affect implant stability. Search Strategy: A literature search was conducted using MEDLINE to identify studies, from simulated laboratory models, animal, to human, related to this topic using the keywords of implant thread, implant macrodesign, thread pitch, thread geometry, helix angle, thread depth, thread width and implant crestal module. Results: The results showed how thread geometry affects the distribution of stress forces around the implant. A decreased thread pitch may positively influence implant stability. Excess helix angles in spite of a faster insertion may jeopardize the ability of implants to sustain axial load. Deeper threads seem to have an important effect on the stabilization in poorer bone quality situations. The addition of threads or microthreads up to the crestal module of an implant might provide a potential positive contribution on bone‐to to‐implant contact as well as on the preservation of marginal bone; nonetheless this remains to be determined. Conclusions: Appraising the current literature on this subject and combining existing data to verify the presence of any association between the selected characteristics may be critical in the achievement of overall implant success. To cite this article:
Abuhussein H, Pagni G, Rebaudi A, Wang H‐L. The effect of thread pattern upon implant osseointegration.
Clin. Oral Impl. Res. 21 , 2010; 129–136.
doi: 10.1111/j.1600‐0501.2009.01800.x     

The biomechanical analysis of relative position between implant and alveolar bone: finite element method

Background: The purpose of this study is to analyze biomechanical interactions in the alveolar bone surrounding implants with smaller‐diameter abutments by changing position of the fixture–abutment interface, loading direction, and thickness of cortical bone using the finite element method. Methods: Twenty different finite element models including four types of cortical bone thickness (0.5, 1, 1.5, and 2 mm) and five implant positions relative to bone crest (subcrestal 1, implant shoulder 1 mm below bone crest; subcrestal 0.5, implant shoulder 0.5 mm below bone crest; at crestal implant shoulder even with bone crest; supracrestal 0.5, implant shoulder 0.5 mm above bone crest; and supracrestal 1, implant shoulder 1 mm above bone crest) were analyzed. All models were simulated under two different loading angles (0 and 45 degrees) relative to the long axis of the implant, respectively. The three factors of implant position, loading type, and thickness of cortical bone were computed for all models. Results: The results revealed that loading type and implant position were the main factors affecting the stress distribution in bone. The stress values of implants in the supracrestal 1 position were higher than all other implant positions. Additionally, compared with models under axial load, the stress values of models under off‐axis load increased significantly. Conclusions: Both loading type and implant position were crucial for stress distribution in bone. The supracrestal 1 implant position may not be ideal to avoid overloading the alveolar bone surrounding implants.