植体弹性模量变化对牙种植体和骨组织应力分布的影响

目的通过三维有限元法分析,探讨植体弹性模量变化对牙种植体和骨组织应力分布的影响,为新型牙种植系统的研究提供实验依据。方法应用螺旋CT数据,建立下颌骨和种植体模型。设定植体弹性模量分别为110、90、70、55和40 GPa,模拟咬合状态,在垂直、水平、斜向分别施加300、100、130 N静止载荷,计算并分析各组在3种载荷下植体周围骨组织和牙种植体各部分的应力。结果随着植体弹性模量的降低,水平和斜向载荷下牙种植体周围皮质骨受到的应力会随之降低,种植体的应力也呈逐渐减小趋势。结论降低牙种植体材料的弹性模量有利于载荷在种植体和周围骨组织中的传导,降低种植义齿晚期失败的风险。     

Comparison of Nanoindentation Measurements Between Osteogenesis Imperfecta Type III and Type IV and Between Different Anatomic Locations (Femur/Tibia versus Iliac Crest)

Nanoindentation was used to compare the intrinsic mechanical properties of bone tissue (iliac crest biopsy) from children with type III and type IV osteogenesis imperfecta (OI). Young's modulus and hardness values were not significantly different between the two clinical severity groups on either cortical or trabecular measurement. In comparing the ratio of modulus over hardness (E/H) between OI type III and IV. The type III bone showed a marginally significant decrease for cortical bone and significant decrease for trabecular bone, which indicated that the OI type III bone was more brittle than OI type IV bone at the tissue level. In addition, nanoindentation measurements of the bone tissue harvested at femur/tibia from the same patients were compared with the results from the iliac crest biopsy. Young's modulus and hardness values were not significantly different between the two anatomic locations in either cortical or trabecular measurements. The ratio of E/H was not significantly different between the two groups. Results indicate that intrinsic modulus, hardness, and indentation deformation pattern (E/H) of OI bone tissues are not significantly different at long bone (midshaft of femur/tibia) and iliac crest. We observed that age (1.9 to 13.2 years) did not influence OI bone tissue intrinsic mechanical properties.     

Comparison of nanoindentation measurements between osteogenesis imperfecta Type III and Type IV and between different anatomic locations (femur/tibia versus iliac crest)

Nanoindentation was used to compare the intrinsic mechanical properties of bone tissue (iliac crest biopsy) from children with type III and type IV osteogenesis imperfecta (OI). Young's modulus and hardness values were not significantly different between the two clinical severity groups on either cortical or trabecular measurement. In comparing the ratio of modulus over hardness (E/H) between OI type III and IV. The type III bone showed a marginally significant decrease for cortical bone and significant decrease for trabecular bone, which indicated that the OI type III bone was more brittle than OI type IV bone at the tissue level. In addition, nanoindentation measurements of the bone tissue harvested at femur/tibia from the same patients were compared with the results from the iliac crest biopsy. Young's modulus and hardness values were not significantly different between the two anatomic locations in either cortical or trabecular measurements. The ratio of E/H was not significantly different between the two groups. Results indicate that intrinsic modulus, hardness, and indentation deformation pattern (E/H) of OI bone tissues are not significantly different at long bone (midshaft of femur/tibia) and iliac crest. We observed that age (1.9 to 13.2 years) did not influence OI bone tissue intrinsic mechanical properties.     

Investigation into the material properties of beech wood and cortical bone

When testing medical implants it is very important to be able to test the implant using a suitable material. In the case of orthopaedic implants the optimum material is bone. Beech wood is considered a suitable substitute for bone as it has a similar Young's modulus in tension. Although it is widely used, no actual comparison of the two materials has been undertaken. The aim of this study was to compare the material properties of beech wood and cortical bone using conventional compression tests. Cortical bone samples 4 mm in diameter and 20 mm in length, were prepared from the tibia of an amputated leg. Beech wood samples were prepared to the same specifications. In compression, the Young's modulus for cortical bone was found to be 27+/-9.9 GPa (mean +/- standard deviation) and for beech wood 2.6+/-1.7 GPa. The failure load for cortical bone was 911+/-207 N and 732+/-62 N for beech wood. Although beech wood has been used as a substitute for bone in some studies, this study has shown that there are significant differences in the properties of the two materials when they are subjected to compression.     

In vivo evaluation of bone-bonding ability of RGD-coated porous implant using layer-by-layer electrostatic self-assembly

RGD has been demonstrated to improve implant osseointegration. However, few studies are known about an effect of RGD coating on a bone-bonding ability of screw-shaped porous implant. The aim of this study was to investigate the effect of RGD coating using the layer-by-layer self-assembly technique on the bone-bonding ability of porous implant. 60 implants of 10 mm in length (30 control and 30 RGD-coated) were inserted into femurs of 30 rabbits and 30 implants of 8 mm in length (15 control and 15 RGD-coated) were inserted into tibias of 15 rabbits. At 4, 8, and 12 weeks post-implantation, femurs and tibias were retrieved and prepared for removal torque tests (RTQ) and histomorphometric evaluation, respectively. No differences were found in the RTQ values between two implants at 4 weeks (p = 0.932). There were statistical significances in the RTQ values at 8 and 12 weeks (p = 0.002, 0.001, respectively). New bone was formed on both implant surfaces. The bone-implant contact pattern appeared to produce a broad-based direct contact in both implants. The RGD-coated implants showed a significantly greater BIC in the threads inside the cortical bone compared with the control implants at 4, 8, and 12 weeks (p = 0.024, 0.041, 0.022, respectively). No differences were found in the bone area within the same threads between two implants at 4 weeks (p = 0.806) whereas differences were found at 8 and 12 weeks (p = 0.009, 0.031, respectively). It was concluded that RGD coating using the layer-by-layer self-assembly technique has a positive effect on the bone-bonding ability of porous implant.     

Mechanical and morphological variation of the human lumbar vertebral cortical and trabecular bone.

The nanoindentation technique was used to characterize the variation in the elastic modulus and hardness of human lumbar vertebral cortical and trabecular bone. The elastic modulus (and in most cases, the hardness as well) of axially aligned trabeculae cut in the transverse direction was significantly greater than in other orientations of vertebral cortical and trabecular bone. In all cases, the elastic modulus and hardness of bone in the load-bearing direction was greater than in corresponding bone types cut in the other directions. Scanning electron micrographs of cortical shell revealed the Haversian-like canal systems expected in secondary cortical bone, but it was difficult to differentiate by morphology cortical from trabecular bone in the human lumbar vertebrae.     

The influence of Young's modulus of loaded implants on bone remodeling: an experimental and numerical study in the goat knee

The aim of this study was to examine the influence of the Young's modulus of the implant material on the bone remodeling in a loaded condition. A combined animal experimental and computational study was set up. The animal experimental group comprised of 16 Saanen goats, each receiving one titanium implant (Young's modulus 110 GPa) and one high-density polyethylene (HDPE) implant (Young's modulus 1 GPa) in the left femoral condyle. Both types of implants received a titanium coating of 100 nm thickness. The implants protruded in the knee joint space and were directly weight bearing. The first group of eight goats was sacrificed after 6 weeks of loading and the second group of eight goats after 6 months of loading. The 16 femoral condyles with the 32 implants were prepared for microfocus computed tomography (micro-CT) scanning and histological sectioning. Three-dimensional trabecular bone parameters were calculated on the micro-CT images for the zones neck, middle, and apex of the implant. The percent of bone contact with the implant was measured on longitudinal histological sections. An axisymmetric finite element (FE) model was created to compare peri-implant bone strains and relative motion between a titanium and a HDPE implant for the experimental loading condition, and to assess the influence of different bone-implant interface (contact) conditions. From the statistical analysis of the 3D bone parameters, the difference between the titanium and HDPE implants was not significantly different (p > 0.05) between the zones (neck, middle, and apex) for both groups of goats. The implants could be considered in their entirety. After 6 weeks of loading, the PE implant presented lower connectivity and smaller marrow spaces in the circular region of 0-500 microm. In the region 500-1500 microm more bone volume was present for the PE implant. After 6 months, the PE implants showed more bone volume and thicker trabeculae than the titanium implants for the entire length of the implant. This effect was already present in the smallest region of interest, 0-500 microm. After 6 months more fibrous encapsulation was found around titanium implants. FE results demonstrated a substantial influence of the interface conditions on peri-implant strains and relative motion. For interface conditions that were representative for the early postoperative situation (involving press-fit and friction), differences in peri-implant bone strain distributions between titanium and HDPE could be related to the experimentally observed differences in amounts of bone and fibrous encapsulation. In contrast, differences in relative motion did not seem to play a role. Both the experimental and computational results suggest that implant stiffness can affect the peri-implant tissue response, which may be related to differences in peri-implant strains.     

Bioactive glass/polymer composite materials with mechanical properties matching those of cortical bone

Stress shielding resulting from mismatch in dynamic mechanical properties contributes to the reduced stability of osseous implants. Our objective was to develop biocompatible composites having mechanical properties similar to those of cortical bone. Polymers of urethane dimethacrylate (UDMA) and 2-hydroxyethyl methacrylate (HEMA, 0-20%) and composites containing bioactive glass particles (70% SiO(2), 25% CaO, and 5% P(2)O(5)), with or without silane treatment were prepared. Young's moduli of composites containing silane-treated glass (16 GPa) were significantly greater than those of composites containing untreated glass (12-13 GPa) or of unfilled polymers (5-6 GPa). Bioactive glass reduced water sorption by the composites and incorporation of silane-treated glass prevented HEMA-induced increases in water sorption. Osteoblast-like cells attached equally well to UDMA polymer and composite containing silane-treated bioactive glass. Thus, silane treatment improved the mechanical properties of bioactive glass composites without compromising biocompatibility. This material has a Young's modulus comparable to that of cortical bone. Therefore, silane-treated bioactive glass composites, when used as implant or cement materials, would reduce stress shielding and improve implant stability.     

Elastic Modulus of Cetacean Auditory Ossicles

In order to model the hearing capabilities of marine mammals (cetaceans), it is necessary to understand the mechanical properties, such as elastic modulus, of the middle ear bones in these species. Biologically realistic models can be used to investigate the biomechanics of hearing in cetaceans, much of which is currently unknown. In the present study, the elastic moduli of the auditory ossicles (malleus, incus, and stapes) of eight species of cetacean, two baleen whales (mysticete) and six toothed whales (odontocete), were measured using nanoindentation. The two groups of mysticete ossicles overall had lower average elastic moduli (35.2 ± 13.3 GPa and 31.6 ± 6.5 GPa) than the groups of odontocete ossicles (53.3 ± 7.2 GPa to 62.3 ± 4.7 GPa). Interior bone generally had a higher modulus than cortical bone by up to 36%. The effects of freezing and formalin‐fixation on elastic modulus were also investigated, although samples were few and no clear trend could be discerned. The high elastic modulus of the ossicles and the differences in the elastic moduli between mysticetes and odontocetes are likely specializations in the bone for underwater hearing. Anat Rec, 297:892–900, 2014. © 2014 Wiley Periodicals, Inc.     

Alteration of dentin–enamel mechanical properties due to dental whitening treatments

The mechanical properties of dentin and enamel affect the reliability and wear properties of a tooth. This study investigated the influence of clinical dental treatments and procedures, such as whitening treatments or etching prior to restorative procedures. Both autoclaved and non-autoclaved teeth were studied in order to allow for both comparison with published values and improved clinical relevance. Nanoindentation analysis with the Oliver–Pharr model provided elastic modulus and hardness across the dentin–enamel junction (DEJ). Large increases were observed in the elastic modulus of enamel in teeth that had been autoclaved (52.0 GPa versus 113.4 GPa), while smaller increases were observed in the dentin (17.9 GPa versus 27.9 GPa). Likewise, there was an increase in the hardness of enamel (2.0 GPa versus 4.3 GPa) and dentin (0.5 GPa versus 0.7 GPa) with autoclaving. These changes suggested that the range of elastic modulus and hardness values previously reported in the literature may be partially due to the sterilization procedures. Treatment of the exterior of non-autoclaved teeth with Crest Whitestrips?, Opalescence? or UltraEtch? caused changes in the mechanical properties of both the enamel and dentin. Those treated with Crest Whitestrips? showed a reduction in the elastic modulus of enamel (55.3 GPa to 32.7 GPa) and increase in the elastic modulus of dentin (17.2 GPa to 24.3 GPa). Opalescence? treatments did not significantly affect the enamel properties, but did result in a decrease in the modulus of dentin (18.5 GPa to 15.1 GPa). Additionally, as expected, UltraEtch? treatment decreased the modulus and hardness of enamel (48.7 GPa to 38.0 GPa and 1.9 GPa to 1.5 GPa, respectively) and dentin (21.4 GPa to 15.0 GPa and 1.9 GPa to 1.5 GPa, respectively). Changes in the mechanical properties were linked to altered protein concentration within the tooth, as evidenced by fluorescence microscopy and Fourier transform infrared spectroscopy.     

An evaluation of variables influencing implant fixation by direct bone apposition

A systematic mechanical and histologic evaluation of design variables affecting bone apposition to various biocompatible materials was undertaken. The variables investigated included material elastic modulus, material surface texture, as well as material surface composition. The implant materials included polymethylmethacrylate (PMMA), low-temperature isotropic (LTI) pyrolytic carbon, commercially pure (C.P.) titanium, and aluminum oxide (Al2O3). Implant surface texture was varied by either polishing or grit-blasting the various materials. Implant surface composition was varied by applying a coating of ultra-low temperature isotropic (ULTI) pyrolytic carbon to the various implants. A total of 12 types of implants were evaluated in vivo by placement transcortically in the femora of adult mongrel dogs for a period of 32 weeks. Following sacrifice, mechanical push-out testing was performed to determine interface shear strength and interface shear stiffness. The results obtained from mechanical testing indicate that for implants fixed by direct bone apposition, interface stiffness and interface shear strength are not significantly affected by either implant elastic modulus or implant surface composition. Varying surface texture, however, significantly affected the interface response to the implants. For each elastic modulus group the roughened surfaced implants exhibited greater strengths than the corresponding smooth surfaced implants. Undecalcified histologic evaluation of the implants demonstrated that the roughened implants exhibited direct bone apposition, whereas the smooth implants exhibited various degrees of fibrous tissue encasement. Thus, for implants utilizing direct bone apposition fixation, it appears that of the parameters investigated, implant surface texture is the most significant.     

Nano-mechanics of bone and bioactive bone cement interfaces in a load-bearing model

Many bioactive bone cements were developed for total hip replacement and found to bond with bone directly. However, the mechanical properties at the bone/bone cement interface under load bearing are not fully understood. In this study, a bioactive bone cement, which consists of strontium-containing hydroxyapatite (Sr-HA) powder and bisphenol-alpha-glycidyl dimethacrylate (Bis-GMA)-based resin, was evaluated in rabbit hip replacement for 6 months, and the mechanical properties of interfaces of cancellous bone/Sr-HA cement and cortical bone/Sr-HA cement were investigated by nanoindentation. The results showed that Young's modulus (17.6+/-4.2 GPa) and hardness (987.6+/-329.2 MPa) at interface between cancellous bone and Sr-HA cement were significantly higher than those at the cancellous bone (12.7+/-1.7 GPa; 632.7+/-108.4 MPa) and Sr-HA cement (5.2+/-0.5 GPa; 265.5+/-39.2 MPa); whereas Young's modulus (6.3+/-2.8 GPa) and hardness (417.4+/-164.5 MPa) at interface between cortical bone and Sr-HA cement were significantly lower than those at cortical bone (12.9+/-2.2 GPa; 887.9+/-162.0 MPa), but significantly higher than Sr-HA cement (3.6+/-0.3 GPa; 239.1+/-30.4 MPa). The results of the mechanical properties of the interfaces were supported by the histological observation and chemical composition. Osseointegration of Sr-HA cement with cancellous bone was observed. An apatite layer with high content of calcium and phosphorus was found between cancellous bone and Sr-HA cement. However, no such apatite layer was observed at the interface between cortical bone and Sr-HA cement. And the contents of calcium and phosphorus of the interface were lower than those of cortical bone. The mechanical properties indicated that these two interfaces were diffused interfaces, and cancellous bone or cortical bone was grown into Sr-HA cement 6 months after the implantation.     

The effects of embedding material, loading rate and magnitude, and penetration depth in nanoindentation of trabecular bone

Understanding the pathophysiology of metabolic bone disease requires the characterization of both the quantity as well as the quality (i.e., microarchitecture and material properties) of the bone tissue. Nanoindentation provides a powerful yet simple method to measure the nano/micro mechanical properties of bone, but no uniform testing methodology exists. This study examines the effects of embedding materials, rate and depth of indentation, and storage time on the measured modulus. Nineteen trabecular bone samples were evaluated for the study. Although there was an 8-fold increase in the stiffness of the soft to hard epoxy, bone tissue modulus was not affected by the stiffness of the embedding materials, but hardness was affected by both the embedding material modulus, for example from 0.70 +/- 0.20 GPa (ME(low)) to 0.45 +/- 0.21 GPa (ME(Med)) (p < 0.01), and viscosity (p < 0.01). No significant differences were found with regard to the tested rates and depths of indentation for either elastic modulus or hardness. The tissue modulus tested at the 6-month time point was significantly greater in comparison with that tested at 0 or 3 months (p < 0.01). The hardness, however, did not significantly change over the span of 6 months. The results show that while nanoindentation is powerful, it is particularly sensitive to certain testing variables.     

Quality of alveolar bone--Structure-dependent material properties and design of a novel measurement technique

The evidence for the efficiency of clinical methods used to assess the quality of alveolar bone in terms of a density measure prior to and during dental implant surgery is limited. The aim of this paper is to describe the biomechanical background which can be used as a basis for determining the bone quality by measuring the elastic properties of the bone and to design a novel device for the determination of the bone quality during dental implant surgery. Applying material mechanical equations for porous and cellular structured models, the elastic material properties (modulus of elasticity) of cellular and cortical bone as porous structures were approximated over the whole range of relative bone mineral density of trabecular and cortical bone. Based on a circular disc with a central hole reflecting a horizontal cross-section of an implant socket, the mechanical effects of expanding the central hole were studied. Subsequently, the clinical situation of a socket prepared for the placement of a dental implant (depth: 10?mm; diameter 3.5?mm) was simulated using three-dimensional (3D) finite element analysis. A loading device (thickness: 3.5?mm) was placed in the trabecular part of the socket and expanded, while the resulting pressure was recorded and used for the calculation of an elastic modulus. Finite element analysis revealed that it was possible to estimate the bone quality by applying the measurement technique proposed. Maximum deviations of 6% of the experimentally determined elastic modulus from the setpoint elastic modulus were found. Measuring the internal pressure in a drill hole, e.g., in an implant socket caused by a defined expansion of a rotational symmetric loading device, could be used for establishing a clinically meaningful test system for the objective classification of alveolar bone.     

Estimation of the elastic modulus of child cortical bone specimens via microindentation

Purpose: Non-pathological child cortical bone (NPCCB) studies can provide clinicians with vital information and insights. However, assessing the anisotropic elastic properties of NPCCB remains a challenge for the biomechanical engineering community. For the first time, this paper provides elastic moduli values for NPCCB specimens in two perpendicular directions (longitudinal and transverse) and for two different structural components of bone tissue (osteon and interstitial lamellae).

Materials and Methods: Microindentation is one of the reference methods used to measure bone stiffness. Here, 8 adult femurs (mean age 82 ± 8.9 years), 3 child femurs (mean age 13.3 ± 2.1 years), and 16 child fibulae (mean age 10.2 ± 3.9 years) were used to assess the elastic moduli of adult and child bones by microindentation.

Results: For adult specimens, the mean moduli measured in this study are 18.1 (2.6) GPa for osteons, 21.3 (2.3) GPa for interstitial lamellae, and 13.8 (1.7) GPa in the transverse direction.

For child femur specimens, the mean modulus is 14.1 (0.8) GPa for osteons, lower than that for interstitial lamellae: 15.5 (1.5) GPa. The mean modulus is 11.8 (0.7) GPa in the transverse direction. Child fibula specimens show a higher elastic modulus for interstitial lamellae 15.8 (1.5) than for osteons 13.5 (1.6), with 10.2 (1) GPa in the transverse direction.

Conclusion: For the first time, NPCCB elastic modulus values are provided in longitudinal and transverse directions at the microscale level.     

Tribo-mechanical characterization of rough, porous and bioactive Ti anodic layers

Rough and porous titanium oxide layers, which are important features for improving the osseointegration of Ti implants with bone tissues, are obtained through the technique of anodic oxidation. The thicknesses of such coatings are typically in the order of micrometers, and their mechanical characterization can be assessed by instrumented indentation, provided that the composite nature of the surface is considered. Titania anodic layers were produced on Ti under galvanostatic mode using Ca-P-based electrolytes (a mixture of (CH3COO)2Ca?H2O and NaH2PO(4)?2H2O), employing current densities (J) of 150 mA/cm2 and 300 mA/cm2. The structure and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy with electron dispersive X-ray spectroscopy (SEM/EDS), and profilometry, and the chemical features were characterized by X-ray photoelectron spectroscopy (XPS). TiO2 layers presented the crystalline phases rutile and anatase, and incorporation of Ca and P presented as a calcium phosphate compound. The porosity, roughness, and thickness increased with J. Analytical methods were employed to obtain the modified layers' elastic modulus and hardness from instrumented indentation data, deducting the substrate and roughness effects. The elastic moduli were about 40 GPa for both values of J, which are similar to the values for human bones (10-40 GPa). The hardness decreased with indentation load, varying from 5 GPa at the near surface to 1 GPa at the layer-substrate interface. Such hardness behavior is a consequence of the surface brittleness under normal loading. Additional scratch tests using an acute tip indicated that the layer integrity under shear forces was 220 mN (J=150 mA/cm2) and 280 mN (J=300 mA/cm2). TiO2 layers produced with both current densities presented good results for in vitro bioactivity tests using simulated body fluid (SBF) solution, which can be attributed to a combined effect of the microstructure, layer porosity, and hydroxyl radicals in plenty at the near surface.     

The effect of zoledronic acid on the intrinsic material properties of healing bone: an indentation study

BACKGROUND: Bisphosphonates are commonly used for the treatment of osteoporosis and have recently been shown to increase bone mineral parameters and strength in endochondral fracture repair. There is concern, however, that BPs may negatively affect bone material properties. METHODS: Nanoindentation was performed on femoral fracture samples of rats that had undergone closed fracture healing for six weeks to determine hardness and elastic modulus. The rats had received either intravenous saline or a single intravenous dose of zoledronic acid at zero, one or two weeks post fracture (n = 3 per group). FINDINGS: The mean elastic modulus and hardness of mineralised tissue in control calluses were mean 16.4 GPa (S.D. 2.3) and mean 0.65 GPa(S.D. 0.1), respectively. There was no significant change in these parameters with zoledronic acid treatment. INTERPRETATION: The results from this preliminary data suggest that single dose zoledronic acid treatment in fracture healing may not adversely affect the intrinsic properties of callus bone tissue. Single dose bisphosphonate may be a viable treatment for augmenting fracture repair without negatively affecting the material properties.     

Biocompatibility of corrosion-resistant zeolite coatings for titanium alloy biomedical implants

Titanium alloy, Ti6Al4V, is widely used in dental and orthopedic implants. Despite its excellent biocompatibility, Ti6Al4V releases toxic Al and V ions into the surrounding tissue after implantation. In addition, the elastic modulus of Ti6Al4V (～110 GPa) is significantly higher than that of bone (10–40 GPa), leading to a modulus mismatch and consequently implant loosening and deosteointegration. Zeolite coatings are proposed to prevent the release of the toxic ions into human tissue and enhance osteointegration by matching the mechanical properties of bone. Zeolite MFI coatings are successfully synthesized on commercially pure titanium and Ti6Al4V for the first time. The coating shows excellent adhesion by incorporating titanium from the substrate within the zeolite framework. Higher corrosion resistance than the bare titanium alloy is observed in 0.856 M NaCl solution at pHs of 7.0 and 1.0. Zeolite coatings eliminate the release of cytotoxic Al and V ions over a 7 day period. Pluripotent mouse embryonic stem cells show higher adhesion and cell proliferation on the three-dimensional zeolite microstructure surface compared with a two-dimensional glass surface, indicating that the zeolite coatings are highly biocompatible.     

人体主动脉瓣膜钙化组织的力学性质

目的采用纳米压痕测试方法,测量人体主动脉瓣取出物的钙化组织的材料力学性能。方法采集5名主动脉瓣狭窄患者的瓣叶取出物,选取钙化瓣叶进行纳米压痕测试,获得钙化组织弹性模量、硬度等材料力学参数。结果瓣叶钙化组织的弹性模量为(15.69±3.89) GPa,硬度为(0.59±0.15) GPa。结论通过纳米压痕测试方法得到瓣叶钙化组织的弹性模量和硬度,为瓣膜的生物力学研究提供实验数据参考。     

Bone growth in rapid prototyped porous titanium implants

Two porous titanium implants with a pore size diameter of 800 and 1200 microm (Ti800 and Ti1200) and an interconnected network were manufactured using rapid prototyping. Their dimensions and structure matched those of the computer assisted design. The porosity of the implants was around 60%. Their compressive strength and Young's modulus were around 80 MPa and 2.7 GPa, respectively. These values are comparable to those of cortical bone. The implants were implanted bilaterally in the femoral epiphysis of 15 New Zealand White rabbits. After 3 and 8 weeks, abundant bone formation was found inside the rapid prototyped porous titanium implants. For the Ti1200 implants, bone ingrowth was (23.9 +/- 3.5)% and (10.3 +/- 2.8)%, respectively. A significant statistical difference (p < 0.05) was found for bone ingrowth in the Ti1200 between the two delays. The percentage of bone directly apposited on titanium was (35.8 +/- 5.4)% and (30.5 +/- 5.0)%. No significant difference was found for bone-implant contact between the different time periods and pore sizes. This work demonstrates that manufacturing macroporous titanium implants with controlled shape and porosity using a rapid prototyping method is possible and that this technique is a good candidate for orthopedic and maxillofacial applications.