3 种不同髁突头部形态全颞下颌关节假体的生物力学研究

目的 对个性化聚醚醚酮(polyetheretherketone, PEEK)全颞下颌关节假体进行三维建模,通过有限元分析 3 种不同髁突头部形态(原型、80% 原型及圆柱形)假体的应力分布特征,评估 3 种不同髁突头部形态对 PEEK 全颞 下颌关节假体稳定性、关节运动以及关节窝的影响。 方法 建立颅颌面及 PEEK 全颞下颌关节假体有限元分析模 型Ⅰ、Ⅱ、Ⅲ,分析在牙尖交错位、切 颌位、左侧磨牙颌位及右侧磨牙颌位 4 种不同咬合条件下,关节窝假体、髁突 假体、钛钉最大应力,下颌骨应力、应变分布,以及 3 种模型的最大位移。 结果 3 种模型 PEEK 全关节假体及螺钉 的最大应力分别为 35. 22、16. 73 MPa,均低于其材料的屈服强度;模型Ⅰ、Ⅱ、Ⅲ下颌骨最大应力分别为 41. 47、42. 84、 56. 92 MPa,应变分别为 3. 896×10-3 、2. 175×10-3 、4. 641×10-3 。 3 种模型的最大位移为 209. 0 μm,位于模型Ⅲ的左侧下 颌角处。 结论 3 种不同髁突头部形态的个性化 PEEK 全颞下颌关节假体均显示出较为均匀的应力应变分布,但髁 突头部形态为 80% 原型假体的力学效果更好。 研究结果为 PEEK 全颞下颌关节的设计提供一定理论依据。     

颞下颌关节的生物力学

颞下颌关节是人体最为复杂,精细的关节之一,具有负重的功能,关节软骨是具有低渗透性的多孔粘弹性介质,生理状态下在软骨内部存在胶原－蛋白多糖－水凝胶网状结构应力缓冲系统。关节盘是特殊类型的结缔组织,不属纤维软骨,是髁突和关节窝之间的应力集中缓冲器。关节盘后组织具有高度的顺应性,在关节运动中发挥容积补偿作用,关节外侧壁是囊－韧带结构的复合体,拉伸强度和拉伸刚度较弱,长期的口腔副功能易使结构处于超负荷状态     

包含颞下颌关节的下颌骨有限元建模

为获得颞下颌关节下颌骨的应力分布提供更为有效的有限元模型。用Mimics10．0导入正常人的颌面CT建立其下颌各部位的有限元模型,通过CAE软件ABAQUS 6．10进行有限元分析。获得了完整的下颌骨、颞下颌关节有限元模型,及后牙咬合状态下模型各部位应力分布等数据。通过分析数据发现,关节盘高应力区主要集中在关节盘中带和后带,而关节盘各部分应力表现为关节盘颊侧应力高于舌侧,顶部应力高于底部,中带平均应力最大,后带次之,前带最小。     

狗颞颌关节盘的流变特性研究

本文把狗的颞颌关节盘分成前、中、后三个区域作单向拉伸、应力松弛及循环加载实验,得出了在不同区域,试件在不同阶跃应变作用下的瞬时弹性响应及平衡模量,应用拟线性粘弹性理论分析实验结果,得出该关节盘软骨不同区域的弹性响应及归一化松弛函数,从而得到它在不同区域一维拉伸时的本构方程。实验表明,理论分析与实验结果吻合较好。     

青海高原牦牛和湖区水牛下肢骨强度的实验研究

目的　了解青海高原牦牛和湖区水牛股骨、胫骨的抗拉强度、抗压强度、抗折 (弯曲 )强度和抗扭 (剪切 )强度。方法　分别取 6头成年青海高原牦牛和 6头湖区水牛的下肢骨 ,按测试要求作成标准件 ,每项测试任取 3个不同源的试样 ,用常规的力学试验设备和方法 ,分别进行两种牛股骨和胫骨的拉伸、压缩、抗折、扭转 4项试验。结果　牛股骨拉伸极限应力 (1 0 6.3 5± 3 .4 5 )MPa ,压缩极限应力 (1 2 7.60± 2 .65 )MPa ,抗折极限应力 (2 2 5 .9± 4 .1 )MPa ,扭转极限应力 (5 3 .4 5± 1 .5 5 )MPa ,胫骨拉伸极限应力 (1 1 4 .96± 1 .4 6)MPa ,压缩极限应力 (1 84 .75± 3 .2 5 )MPa,抗折极限应力 (2 1 1 .3 5± 2 .4 5 )MPa ,扭转极限应力 (5 1 .9± 0 .5 )MPa。湖区水牛胫骨拉伸极限应力 (1 2 8.1± 1 1 )MPa ,压缩极限应力(1 95 .8± 9.4 )MPa,抗折极限应力 (1 67.4± 1 2 .7)MPa ,扭转极限应力 (5 4 .2 5± 0 .75 )MPa。结论　获得了青海高原牦牛和湖区水牛下肢骨极限应力的初步数据     

关节盘移位对颞下颌关节内应力分布的影响

目的 通过对不同关节盘移位的数值模拟,探究各种移位情况下颞下颌关节（temporomandibular joint,TMJ）内各结构的应力分布规律。方法 依据CT图像,建立包含下颌骨、全牙列、关节盘和关节软骨的正常TMJ三维有限元模型;参考关节盘前、后、外、内移位的临床特征,建立对应的4个模型。关节盘与关节软骨间考虑接触,用缆索元模拟下颌韧带和关节盘附着,施加正中咬合荷载。结果 前移位将导致关节盘中带产生过高的压应力,达到3.23 MPa;后、内、外移位时关节盘的整体应力水平比前移位和正常TMJ高;各种移位都使关节结节后斜面的应力值大幅度增加,但对髁突关节面的影响却不大。结论 各种移位都将导致关节盘和关节结节后斜面产生过高的应力,且后、内、外移位更为危险,更容易造成关节结构和功能的损伤。     

仿生咀嚼机器人弹性颞下颌关节设计与性能分析

咀嚼机器人在义齿材料测试和下颌康复训练领域具有广阔的应用前景,而颞下颌关节的机构型式是影响咀嚼机器人性能表现的重要因素。鉴于目前弹性元件已在仿生机器人领域得到广泛应用,因此本文在点接触高副的基础上采用弹性元件模拟颞下颌关节内关节盘缓冲振荡的生物力学特点,形成弹性颞下颌关节机构型式;然后,本文探讨了弹性颞下颌关节对咀嚼机器人在自由度、运动学与动力学等方面的影响,根据关节面几何约束对颞下颌关节的位置与速度进行运动学分析,并进行基于拉格朗日方程的动力学分析;最后,使用响应面法对弹性元件预载荷以及刚度取值的影响进行分析。本文结果表明,弹性颞下颌关节能够有效保证关节的灵活运动与稳定受力。综上,本文所提出的弹性颞下颌关节机构方案进一步提升了咀嚼机器人仿生性,也为粘弹性关节盘的仿生设计提供了新思路。     

印戒细胞淋巴瘤一例

患者男 ,44岁。已婚。因左下颌、右腹股沟包块进行性增大 2个月余 ,于 1999年 12月 2 5日入院。 2个月前左颌下、右腹股沟处先后各出现一个蚕豆大小的包块 ,局部不痛 ,全身不发热但有轻度全身不适。 1个月前双腋下均又发现有杏核大肿物 ,近期肿物迅速增大 ,全身不适加重。体检 :左颌下可触及一 2 5ｃｍ× 2 5ｃｍ× 2 5ｃｍ椭圆形肿物 ,双腋下各可触及一 4 0ｃｍ× 3 0ｃｍ× 3 0ｃｍ肿物 ,右腹股沟可触及一5 0ｃｍ× 4 0ｃｍ× 3 0ｃｍ的条索状肿物 ,无压痛 ,边界清楚。周围血象 :白细胞 12× 10 9/Ｌ ;分类 :淋巴细胞 0 78,中性粒细…     

正畸减数患者后牙前移对颞下颌关节应力影响的三维有限元分析

背景：颞下颌关节紊乱病与颞下颌关节内有高应力密切相关。减数拔牙后伴随着磨牙位置的改变,建立新的咬合关系往往会导致颞下颌关节内应力环境发生改变。目的：在牙尖交错位时,利用三维有限元模型分析正畸减数拔牙后不同程度磨牙前移下颞下颌关节的应力分布。方法：选择在山东青岛市市立医院口腔正畸科就诊的正常牙合患者1例,收集其锥形束CT和MRI数据,分别建立减数前、减数后上下磨牙前移1/3拔牙间隙(拔除4颗第二前磨牙)及减数后上下磨牙前移2/3拔牙间隙(拔除4颗第二前磨牙)的有限元模型,通过建模软件分析牙尖交错位时颞下颌关节各部位的应力分布。结果与结论：(1)减数前后模型中髁突、关节盘、骨关节窝的受力分布基本一致,髁突的应力主要分布于髁突的前部及顶部,关节盘的应力主要分布于关节盘的中带及外侧,颞骨关节窝的应力主要集中分布在关节窝的前部及顶部。与减数前相比,减数后模型中髁突、关节盘及关节窝的等效应力值减小;正畸减数拔牙后,上下磨牙前移1/3拔牙间隙模型中髁突及关节盘的等效应力值小于上下磨牙前移2/3拔牙间隙模型。(2)从生物力学角度上讲,正畸减数拔牙可以降低颞下颌关节的应力,进而提供良好的生物力学环境。     

一例杂合性白血病

患儿　女 ,12岁 ,体重 38kg。因进行性面色苍白 1月余 ,活动后心慌 2周 ,发热 3天入院。查体 :患儿有轻、中度发热 ,面色苍白 ,唇周无发绀 ,全身皮肤无黄染、皮疹、瘀斑及瘀点。右侧颌下可扪及 2枚 0 .5 cm× 0 .5 cm、0 .4 cm× 0 .4 cm淋巴结 ,质中、活动、无压痛。肝肋下 1.5 cm、剑下 2 .5 cm。无明显骨痛及全身浸润。实验室检查 :白细胞 6 9.9× 10 9/ L ,红细胞 2 .84×10 1 2 / L,血色素 6 2 g/ L,血球压积 0 .187,平均红细胞体积 6 5 .8fl,平均血红蛋白量 2 1.8pg,血小板 111× 10 9/ L。血片分类 :原、幼稚细胞 0 .6 6 ,早幼粒 0…     

Cartilage-like mechanical properties of poly (ethylene glycol)-diacrylate hydrogels

Hydrogels prepared from poly-(ethylene glycol) (PEG) have been used in a variety of studies of cartilage tissue engineering. Such hydrogels may also be useful as a tunable mechanical material for cartilage repair. Previous studies have characterized the chemical and mechanical properties of PEG-based hydrogels, as modulated by precursor molecular weight and concentration. Cartilage mechanical properties vary substantially, with maturation, with depth from the articular surface, in health and disease, and in compression and tension. We hypothesized that PEG hydrogels could mimic a broad range of the compressive and tensile mechanical properties of articular cartilage. The objective of this study was to characterize the mechanical properties of PEG hydrogels over a broad range and with reference to articular cartilage. In particular, we assessed the effects of PEG precursor molecular weight (508?Da, 3.4?kDa, 6?kDa, and 10?kDa) and concentration (10-40%) on swelling property, equilibrium confined compressive modulus (H(A0)), compressive dynamic stiffness, and hydraulic permeability (k(p0)) of PEG hydrogels in static/dynamic confined compression tests, and equilibrium tensile modulus (E(ten)) in tension tests. As molecular weight of PEG decreased and concentration increased, hydrogels exhibited a decrease in swelling ratio (31.5-2.2), an increase in H(A0) (0.01-2.46?MPa) and E(ten) (0.02-3.5?MPa), an increase in dynamic compressive stiffness (0.055-42.9?MPa), and a decrease in k(p0) (1.2?×?10(-15) to 8.5?×?10(-15)?m(2)/(Pa?s)). The frequency-dependence of dynamic compressive stiffness amplitude and phase, as well as the strain-dependence of permeability, were typical of the time- and strain-dependent mechanical behavior of articular cartilage. H(A0) and E(ten) were positively correlated with the final PEG concentration, accounting for swelling. These results indicate that PEG hydrogels can be prepared to mimic many of the static and dynamic mechanical properties of articular cartilage.     

Mechanical properties and cell cultural response of polycaprolactone scaffolds designed and fabricated via fused deposition modeling

A number of different processing techniques have been developed to design and fabricate three-dimensional (3D) scaffolds for tissue-engineering applications. The imperfection of the current techniques has encouraged the use of a rapid prototyping technology known as fused deposition modeling (FDM). Our results show that FDM allows the design and fabrication of highly reproducible bioresorbable 3D scaffolds with a fully interconnected pore network. The mechanical properties and in vitro biocompatibility of polycaprolactone scaffolds with a porosity of 61 +/- 1% and two matrix architectures were studied. The honeycomb-like pores had a size falling within the range of 360 x 430 x 620 microm. The scaffolds with a 0/60/120 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 41.9 +/- 3.5 and 3.1 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 29.4 +/- 4.0 and 2.3 +/- 0.2 MPa, respectively. In comparison, the scaffolds with a 0/72/144/36/108 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 20.2 +/- 1.7 and 2.4 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 21.5 +/- 2.9 and 2.0 +/- 0.2 MPa, respectively. Statistical analysis confirmed that the five-angle scaffolds had significantly lower stiffness and 1% offset yield strengths under compression loading than those with a three-angle pattern under both testing conditions (p < or = 0.05). The obtained stress-strain curves for both scaffold architectures demonstrate the typical behavior of a honeycomb structure undergoing deformation. In vitro studies were conducted with primary human fibroblasts and periosteal cells. Light, environmental scanning electron, and confocal laser microscopy as well as immunohistochemistry showed cell proliferation and extracellular matrix production on the polycaprolactone surface in the 1st culturing week. Over a period of 3-4 weeks in a culture, the fully interconnected scaffold architecture was completely 3D-filled by cellular tissue. Our cell culture study shows that fibroblasts and osteoblast-like cells can proliferate, differentiate, and produce a cellular tissue in an entirely interconnected 3D polycaprolactone matrix.     

Alterations in intermediate filaments expression in disc cells from the rat temporomandibular joint following exposure to continuous compressive force

The articular disc in the temporomandibular joint (TMJ) that serves in load relief and stabilizing in jaw movements is a dense collagenous tissue consisting of extracellular matrices and disc cells. The various morphological configurations of the disc cells have given us diverse names, such as fibroblasts, chondrocyte-like cells and fibrochondrocytes; however, the characteristics of these cells have remained to be elucidated in detail. The disc cells have been reported to exhibit heterogeneous immunoreaction patterns for intermediate filaments including glial fibrillary acidic protein (GFAP), nestin and vimentin in the adult rat TMJ. Because these intermediate filaments accumulate in the disc cells as tooth eruption proceeds during postnatal development, it might be surmised that the expression of these intermediate filaments in the disc cells closely relates to mechanical stress. The present study was therefore undertaken to examine the effect of a continuous compressive force on the immunoexpression of these intermediate filaments and an additional intermediate filament - muscle-specific desmin - in the disc cells of the TMJ disc using a rat experimental model. The rats wore an appliance that exerts a continuous compressive load on the TMJ. The experimental period with the appliance was 5 days as determined by previous studies, after which some experimental animals were allowed to survive another 5 days after removal of the appliance. Histological observations demonstrated that the compressive force provoked a remarkable acellular region and a decrease in the thickness of the condylar cartilage of the mandible, and a sparse collagen fiber distribution in the articular disc. The articular disc showed a significant increase in the number of desmin-positive cells as compared with the controls. In contrast, immunopositive cells for GFAP, nestin and vimentin remained unchanged in number as well as intensity. At 5 days after removal of the appliance, both the disc and cartilage exhibited immunohistological and histological features in a recovery process. These findings indicate that the mature articular cells are capable of producing desmin instead of the other intermediate filaments against mechanical stress. The desmin-positive disc cells lacked α-smooth muscle actin (α-SMA) in this study, even though desmin usually co-exists with α-SMA in the vascular smooth muscle cells or pericytes. Because the precursor of a pericyte has such an immunoexpression pattern during angiogenesis, there is a further possibility that the formation of new vessels commenced in response to the extraordinary compressive force.     

Effect of porosity on the fluid flow characteristics and mechanical properties of tantalum scaffolds

In many cases of traumatic bone injury, bone grafting is required. The primary source of graft material is either autograft or allograft. The use of both material sources are well established, however, both suffer limitations. In response, many grafting alternatives are being explored. This article specifically focuses on a porous tantalum metal grafting material (Trabecular Metaltrade mark) marketed by Zimmer. Twenty-one cylindrical scaffolds were manufactured (66% to 88% porous) and tested for porosity, intrinsic permeability, tangent elastic modulus, and for yield stress and strain behavior. Scaffold microstructural geometries were also measured. Tantalum scaffold intrinsic permeability ranged from 2.1 x 10(-10) to 4.8 x 10(-10) m(2) and tangent elastic modulus ranged from 373 MPa to 2.2 GPa. Both intrinsic permeability and tangent elastic modulus closely matched porosity-matched cancellous bone specimens from a variety of species and anatomic locations. Scaffold yield stress ranged from 4 to 12.7 MPa and was comparable to bovine and human cancellous bone. Yield strain was unaffected by scaffold porosity (average = 0.010 mm/mm). Understanding these structure-function relationships will help complete the basic physical characterization of this new material and will aid in the development of realistic mathematical models, ultimately enhancing future implant designs utilizing this material.     

Assessment of growth factor treatment on fibrochondrocyte and chondrocyte co-cultures for TMJ fibrocartilage engineering

Treatments for patients suffering from severe temporomandibular joint (TMJ) dysfunction are limited, motivating the development of strategies for tissue regeneration. In this study, co-cultures of fibrochondrocytes (FCs) and articular chondrocytes (ACs) were seeded in agarose wells, and supplemented with growth factors, to engineer tissue with biomechanical properties and extracellular matrix composition similar to native TMJ fibrocartilage. In the first phase, growth factors were applied alone and in combination, in the presence or absence of serum, while in the second phase, the best overall treatment was applied at intermittent dosing. Continuous treatment of AC/FC co-cultures with TGF-β1 in serum-free medium resulted in constructs with glycosaminoglycan/wet weight ratios (12.2%), instantaneous compressive moduli (790 kPa), relaxed compressive moduli (120 kPa) and Young's moduli (1.87 MPa) that overlap with native TMJ disc values. Among co-culture groups, TGF-β1 treatment increased collagen deposition ～20%, compressive stiffness ～130% and Young's modulus ～170% relative to controls without growth factor. Serum supplementation, though generally detrimental to functional properties, was identified as a powerful mediator of FC construct morphology. Finally, both intermittent and continuous TGF-β1 treatment showed positive effects, though continuous treatment resulted in greater enhancement of construct functional properties. This work proposes a strategy for regeneration of TMJ fibrocartilage and its future application will be realized through translation of these findings to clinically viable cell sources.     

A New Method to Determine Rate-dependent Material Parameters of Corneal Extracellular Matrix

The cornea protects internal ocular contents against external insults while refracting and transmitting the incoming light onto the lens. The biomechanical properties of the cornea are largely governed by the composition and structure of the stromal layer which is an extracellular matrix composed of collagen fibrils embedded in a hydrated soft matrix. The mechanical behavior of the corneal stroma has commonly been characterized using uniaxial tensile tests and inflation experiments. In the present study, unconfined compression experiments were used to investigate the influence of loading rates on compressive behavior of nineteen porcine corneal specimens. The experiments were performed at ramp displacement rates 0.15 μm/s (eight samples), 0.5 μm/s (six samples), and 1.0 μm/s (five samples). For all tests, a maximum compressive strain of 50% (five strain increments of 4% followed by three strain increments of 10%) was selected. The experimental data was analyzed by a transversely isotropic biphasic model and material parameters, i.e., the in-plane Young’s modulus, the out-of-plane Young’s modulus, and the permeability coefficient were calculated. It was observed that while the permeability coefficient decreased exponentially with increasing compressive strain, the in-plane and out-of-plane Young’s moduli increased exponentially with increasing strain. Furthermore, it was found that the equilibrium stress was almost rate independent.     

Effects of hydrostatic pressure on TMJ disc cells

The effects of mechanical stimuli on TMJ disc cells have yet to be investigated. This study examined for the first time the effect of constant and intermittent hydrostatic pressure (HP) on TMJ disc cells. Guided by studies on articular chondrocytes, the chosen amplitude was 10 MPa, the frequency was 1 Hz for intermittent HP, and the duration was 4 h. A one-time application of the HP stimulus was applied in 2-D and 3-D for gene expression studies. A duty cycle of 2 days on, 1 day off for 1 week of HP stimulus was used for biochemical content studies. In monolayer, the intermittent HP regimen increased collagen II expression, while constant HP increased collagen I expression when compared to the non-loaded control. However, the overall expression of collagen I was much higher than collagen II in both constant and intermittent HP. The expression results correlated well with gross morphology, histology, and biochemical content. At Week 1, the intermittent HP group had a lower content of collagen, 7.5 +/- 0.2 microg/construct, than the non-loaded control group, 18.2 +/- 4.0 microg/construct. The constant HP group showed the highest amount of collagen, 24.5 +/- 1.6 microg/construct. These data show that constant HP at 10 MPa for 4 h produces more collagen I than do the non-loaded control or intermittent HP at 10 MPa and 1 Hz.     

PVA /HA复合水凝胶力学性能分析及有限元模拟

目的通过实验与有限元模拟对羟基磷灰石(HA)改变聚乙烯醇/羟基磷灰石(PVA/HA)复合水凝胶的力学性能本质及其承载特性进行研究。方法在UMT试验机上进行PVA/HA复合水凝胶的压缩及应力松弛实验。通过模拟与实验结果相结合,研究PVA/HA复合水凝胶的承载特性及HA对其性能的影响。结果随着HA含量的增加,PVA/HA复合水凝胶的压缩模量先增大后减小,而渗透系数先减小后增大;HA含量为3%的PVA/HA复合水凝胶压缩模量最大、渗透系数最小,分别为1.25 MPa和1.59×10-3 mm4.N-1.s-1。PVA/HA复合水凝胶的液体承载比例随着施载时间的增加呈现先增加后减小的非线性变化,加入HA的PVA/HA复合水凝胶的液体承载比例明显增加。应力松弛速率随着HA含量增加呈先上升后下降趋势,下压相同位移HA,含量为3%时,PVA/HA复合水凝胶所能分散的应力更多。结论 PVA/HA复合水凝胶内部的承载特性影响着其力学性能,HA含量为3%时的PVA/HA复合水凝胶力学性能最优,更接近于天然关节软骨的力学性能。     

The dependence between the strength and stiffness of cancellous and cortical bone tissue for tension and compression: extension of a unifying principle

A strong positive correlation between the apparent ultimate strength and stiffness of bone tissue that can be expressed by a unified relationship has been observed for cortical bone in tension and low-density cancellous bone in compression. For practical purposes, the existence of a relationship between strength and stiffness is significant in that bone stiffness can be measured in vivo using non-invasive methods. It is generally accepted that bone strength is greater in compression than in tension whereas there is no substantial evidence that bone stiffness in compression is different from that in tension. This might suggest that compressive strength would relate to the stiffness, if at all, in a way that is different from tensile strength. In order to examine similarities and differences in the way strength is associated with stiffness between modes of loading and tissue type, we tested equine cortical bone and bovine cancellous bone in compression and examined these data together with previously reported data from compression testing of human cancellous bone as well as tensile testing of cortical bone from various sources. We have found for cortical bone that (i) the sensitivity of strength to stiffness is the same for tension and compression (p>0.75, ANCOVA), and (ii) the difference between the magnitudes of compressive and tensile strength for cortical bone is the result of an additive, rather than a multiplicative factor (52.1 MPa after adjusting to 1 microstrain/s, p<0.0001, ANOVA). High-density bovine tibial cancellous bone, on the other hand, has a steeper slope for its compressive strength-stiffness relationship than that for cortical bone and human cancellous bone, resulting in a transitional relationship between compressive strength and stiffness for a range of bone types and densities. Based on the current results and previous work, it is suggested that the offset strength in the compressive strength-stiffness relationship may be a direct manifestation of the difference between the compressive and tensile strengths of the bone material that constitutes the building blocks of the bone structure. Deviation of high-density cancellous bone compressive behavior from the other bone types and densities is attributed to stress distribution differences between the bone types.