No evidence to indicate topographic dependency on bone formation around cp titanium implants under masticatory loading

In vitro studies have proved the topographic dependency upon osteogenesis on titanium plate by investigating the cell-adhesion, -shape, -proliferation, -differentiation, ALP activity and osteocalcin production of osteogenic stem cells, MG36, MC3T3-E1 and wild strains of bone formative cells from animal and human. However, this in vivo study on bone growth around cp titanium dental implants under masticatory loading did not demonstrate significant difference among the different surface roughness in the range of Ra 0.4–1.9 μm, Rz 2.8–11.2 μm, Rmax 3.6–28.1 μm and Sm 2.9–41.0 μm, which was estimated by measuring the bone contacts, bone occupancies and bone bonding strengths at the implant/bone marrow interface. It is revealed that the topographic dependency on the osteogenetic activity is apt to be covered with wide variation in bone healing potential under the clinical condition with functional biting load.     

The influence of surface topography on wear debris generation at the cement/bone interface under cyclic loading

The long-term success of a total joint replacement can be undermined by loosening of the implant, generation of wear debris or a combination of both factors. In the present study the influence of the surface morphologies of the bone and cement mantle on loosening of cemented total joint replacements (THJRs) and development of wear debris were studied. Model cemented THJR specimens were prepared in which the femoral canal was textured using specific cutting tools. The specimens were subjected to cyclic loads inducing pure shear fatigue of the cement/bone interface. Changes in both the femoral canal and cement mantle resulting from fatigue were quantified in terms of the surface topography and the volume of wear debris. Loosening occurred with cyclic loading due to degradation of the cement and bone and resulted in the development of cement and bone particles. There was no correlation between the fatigue strength of the interfaces and the volume of wear debris. In general, the change in surface topography of the cement mantle with fatigue decreased with increasing volume of cement interdigitation. Femoral canal surfaces with symmetric profile height distribution (i.e., Gaussian surfaces) resulted in the lowest volume of generated debris.     

A preliminary investigation into the microscopic depassivation of passive titanium implant materials in vitro

A sensitive electrochemical technique has been used to examine the passive state of titanium-based materials in Ringer's physiological solution. At ambient temperature, the alloy Ti-6Al-4V shows transient microscopic breakdown of the passive state induced by the presence of chloride ions, and enhanced by increased acidity. These breakdown events involve highly localized depassivation of the passive surface followed by repassivation. Under similar experimental conditions no breakdown of passive titanium was detected.     

An investigation of an electrode at the interface of a piezoelectric bimaterial space under remote electromechanical loading

A plane strain problem for an electrode situated along the interface of a bimaterial piezoelectric space under remote electromechanical loading is considered. The electrode can be electrically charged, and the total charge is prescribed. The electrode is assumed to be thin, and therefore, all mechanical characteristics as well as the tangential component of the electric field are continuous across the whole interface. Due to a special transformation of the conventional presentations of electromechanical values via sectionally analytic functions, the new presentations convenient for the considered problem solution are found. On the base of these presentations, the problem is reduced to the standard Hilbert problem and solved exactly. All electromechanical values are found in closed analytical form, and their singular fields at the electrode tips are presented in the form of simple analytical formulas as well. As a particular case of the obtained solutions, the associated results for a thin electrode in a homogeneous material are obtained and discussed.     

Tensile and torsional shear strength of the bone implant interface of titanium implants in the rabbit

The effect of three different titanium plasma flame spray coatings on the tensile strength and the effect of macrostructures on the torsional shear strength of the bone implant interface was studied. Titanium cylinders, of 8 mm length and 4 mm diameter, were implanted into distal rabbit femurs. For tensile testing, two porous titanium plasma flame spray coatings, Plasmapore^®, fine-grain Plasmapore^®, 1 dense, unporous coating, Plasmapore^® fine on cylinders with axial grooves, and corundum blasted specimens as control group were used. For torsional loading smooth, and macrostructured cylinders with axial grooves, both with Plasmapore^® fine-coating, were used. After 168 days the implant-bone interface was biomechanically tested. A tensile test and a torsional shear test was performed. The results indicated, that the titanium plasma flame spray coatings did not differ in their tensile interface strength, but yielded a stronger interface as sandblasted surfaces and that the macrostructures did not influence the torsional shear strength.     

Biological response of human bone marrow stromal cells to sandblasted titanium nitride-coated implant surfaces

Titanium nitride (TiN) coating has been proposed as an adjunctive surface treatment aimed to increase the physico-mechanical and aesthetic properties of dental implants. In this study we investigated the biological response of primary human bone marrow stromal cells (BMSC) to TiN-coated sandblasted (TiN-SB) compared to uncoated sandblasted (SB) surfaces. SB and TiN-SB disks were qualitatively and quantitatively analyzed by atomic force microscopy. BMSC were obtained from healthy donors and their adhesion and proliferation on the titanium disks were evaluated by scanning electron microscopy and viability assay. The osteoblastic differentiation, in terms of alkaline phosphatase activity, osteocalcin synthesis, and extracellular mineralization, was assessed by specific immunoenzymatic or spectrophotometric assays. No difference (P > 0.05) between TiN-SB and SB disks was found in terms of any of the investigated parameters. TiN-coating showed to maintain the topographical characteristics of sandblasted titanium surfaces and their biological affinity toward bone precursors.     

A superhydrophilic titanium implant functionalized by ozone gas modulates bone marrow cell and macrophage responses

Bone-forming cells and M? play key roles in bone tissue repair. In this study, we prepared a superhydrophilic titanium implant functionalized by ozone gas to modulate osteoconductivity and inhibit inflammatory response towards titanium implants. After 24 h of ozone gas treatment, the water contact angle of the titanium surface became zero. XPS analysis revealed that hydroxyl groups were greatly increased, but carbon contaminants were largely decreased 24 h after ozone gas functionalization. Also, ozone gas functionalization did not alter titanium surface topography. Superhydrophilic titanium (O₃–Ti) largely increased the aspect ratio, size and perimeter of cells when compared with untreated titanium (unTi). In addition, O₃–Ti facilitated rat bone marrow derived MSCs differentiation and mineralization evidenced by greater ALP activity and bone-like nodule formation. Interestingly, O₃–Ti did not affect RAW264.7 M? proliferation. However, naive RAW264.7 M? cultured on unTi produced a two-fold larger amount of TNFα than that on O₃–Ti. Furthermore, O₃–Ti greatly mitigated proinflammatory cytokine production, including TNFα and IL-6 from LSP-stimulated RAW264.7 M?. These results demonstrated that a superhydrophilic titanium prepared by simple ozone gas functionalization successfully increased MSCs proliferation and differentiation, and mitigated proinflammatory cytokine production from both naive and LPS-stimulated M?. This superhydrophilic surface would be useful as an endosseous implantable biomaterials and as a biomaterial for implantation into other tissues.     

Electron microscopy of the bone-hydroxylapatite interface from a human dental implant

A titanium implant coated with hydroxylapatite was observed after removal from a human jaw. The hydroxylapatite coating and bonded bone were observed in the scanning electron microscope. The bone apatite interface was thinned to electron transparency by a special technique and observed in the transmission electron microscope at high magnification. Bone bonded directly to the apatite coating, and there was no evidence for a foreign-body reaction, fibrous tissue, or any altered structure in bone or ceramic at the bone-apatite interface. There was no transition layer between bone and apatite to atomic resolution. Lattice imaging of the ceramic coating and the direct attachment of bone to it provide evidence that the bone bonds chemically to the apatite. Hydroxylapatite is a most desirable implant material, and coating it on a metal substrate gives a strong, impact-resistant implant.     

Electrochemical investigation of dopamine at the water/1,2-dichloroethane interface

Dopamine is an important neurotransmitter in mammalian central and peripheral nervous systems and is also a medicament to cure some neuropsychosis. In this work, ion transfer (IT), facilitated ion transfer (FIT) of protonated dopamine, and electron transfer (ET) between dopamine and ferrocene are investigated at the water/1,2-dichloroethane (W/DCE) interface. The IT and FIT reactions of protonated dopamine can be observed simultaneously within the same potential window. The experimental results demonstrate that dibenzo-18-crown-6, dibenzo-24-crown-8, and benzo-15-crown-5 work well with the protonated dopamine. The amperometric detection of dopamine based on either the IT or the FIT of protonated dopamine can get rid of the interference of ascorbic acid, and the lowest concentration that can be determined is approximately 0.05 microM by differential pulse voltammetry. For the ET reaction, its kinetics can be evaluated by scanning electrochemical microscopy, and the results show that the relationship between rate constants and driving force at the unmodified W/DCE interface obeys the Butler-Volmer equation in a rather wide potential region. When the W/DCE interface is modified by egg lecithin, the ET rate constants decrease with increasing concentration of egg lecithin, which indicates that egg lecithin hinders the ET reaction. When the driving force is increased to a certain degree, the linear relationship between ET rate constants and the driving force is distorted. These results will be helpful to understand both the pharmacodynamics and the neural signal transmission mechanism of dopamine at biological membranes and also provide a novel way to detect dopamine.     

Quantification of the bone-related mRNAs at the bone/prosthetic interface

Aseptic loosening is one of the major reasons for failure of joint prostheses. The periprosthetic tissue has previously been described microscopically; however, little work has been devoted towards quantitating genes expressed by cells at the materials/tissue interface. This study aims to characterize the phenotypic expression of osteoblasts and test the feasibility of quantifying the level of gene expression in periprosthetic tissue sections by combining in situ hybridization and image analysis techniques. There are many factors to consider when quantifying mRNA, in that comparing labeling between different cDNA probes, these should have comparable length and base comparison. The probes should be labeled with the same specific activity, that is the amount of probe to label added is the same, both between different probes and between batches of the same probe. Chromagen color reactions are variable in that the color development is not always linear and more likely follows a sigmoidal curve. Samples should only be compared when it is known that the reaction has been in the linear range. The image analysis of such staining introduces further factors which should be considered and controlled. Color analysis is a very complex problem with respect to reproducibly analyzing histological sections. The brightness component of the image should be independent of the colors within the image, in conventional RGB (red, green and blue) signalling mode this is not possible, while when using HSI (hue saturation and intensity) mode this becomes possible, and factors like staining intensity and brightness of the image become much more accountable and controllable. With these factors identified, we consider that the quantitative image analysis approach does allow comparison of patterns of bone-related mRNAs and demonstrates differences in expression in these osteogenic factors depending on distance from the prosthesis, tissue type, patient and device. © 1998 Kluwer Academic Publishers     

Antibiotic-decorated titanium with enhanced antibacterial activity through adhesive polydopamine for dental/bone implant

Implant-associated infections, which are normally induced by microbial adhesion and subsequent biofilm formation, are a major cause of morbidity and mortality. Therefore, practical approaches to prevent implant-associated infections are in great demand. Inspired by adhesive proteins in mussels, here we have developed a novel antibiotic-decorated titanium (Ti) material with enhanced antibacterial activity. In this study, Ti substrate was coated by one-step pH-induced polymerization of dopamine followed by immobilization of the antibiotic cefotaxime sodium (CS) onto the polydopamine-coated Ti through catechol chemistry. Contact angle measurement and X-ray photoelectron spectroscopy confirmed the presence of CS grafted on the Ti surface. Our results demonstrated that the antibiotic-grafted Ti substrate showed good biocompatibility and well-behaved haemocompatibility. In addition, the antibiotic-grafted Ti could effectively prevent adhesion and proliferation of Escherichia coli (Gram-negative) and Streptococcus mutans (Gram-positive). Moreover, the inhibition of biofilm formation on the antibiotic-decorated Ti indicated that the grafted CS could maintain its long-term antibacterial activity. This modified Ti substrate with enhanced antibacterial activity holds great potential as implant material for applications in dental and bone graft substitutes.     

Surface topography modulates the osteogenesis in human bone marrow cell cultures grown on titanium samples prepared by a combination of mechanical and acid treatments

Titanium samples of different roughness R_a and morphology were prepared using a combination of mechanical (grinding with a SiC paper or blasting with aluminum oxide particles with 65 or 250 m) and chemical (attack with a sulphuric acid based solution or a hydrofluoric acid based solution) treatments. The biological performance of the prepared surfaces was evaluated using human bone marrow osteoblastic cell cultures. Mechanically treated samples presented different R_a values and surface morphology. The hydrofluoric acid solution was more effective than the sulphuric acid solution in smoothing titanium surface and also in eliminating aluminum contamination resulting from the blasting process. Bone marrow cells seeded on the different titanium samples showed a similar pattern of behavior during cell attachment and spreading. Cells proliferated very well on all the titanium surfaces and cell growth was observed during approximately two to three weeks. The samples treated with the hydrofluoric acid solution presented higher alkaline phosphatase activity. Only the blasted samples treated with the acid solutions allowed seeded bone marrow cells to form a mineralized extracellular matrix. The best biological performance was found in the blasted samples treated with the hydrofluoric acid solution, which could be related to the characteristic microtopography of these samples that presented a homogeneous and smooth roughness.     

TiO2纳米溶胶的界面粒子膜的研究

采用胶溶法制备ＴｉＯ２纳米溶胶．用膜天平分别考察了溶胶在陈化过程中和压缩过程中的气液界面压力变化,并用布儒斯特角显微镜原位观测溶胶界面陈化成膜和压膜成膜的过程,发现新鲜（刚刮净）的溶胶界面没有膜,处于不稳定的状态,随着陈化时间的增加逐渐形成界面膜而变得稳定．而且通过压缩过程也能使无膜的溶胶界面成膜．用电镜观测用水平方法转移出来的界面膜,发现其粒子分布均匀、致密,搁置铜网上一周后再观察,发现生长出单晶．     

Morphology and ultrastructure of the interface between hydroxyapatite-polyhydroxybutyrate composite implant and bone

A composite of polyhydroxybutyrate (PHB) polymer, reinforced with synthetic hydroxyapatite (HA) particles, with potential as a bone-analogue material, was examined microscopically using scanning electron microscopy and transmission electron microscopy. These imaging techniques provide the means of understanding and monitoring the morphological and structural behaviour of retrieved implants. Scanning electron microscopy was used to assess the overall mechanism of new bone formation at the implant interface after up to 6 months implantation. This procedure was followed by a detailed ultrastructural examination at lattice plane resolution level, using high resolution electron microscopy and selected area diffraction of the regions showing bone apposition. Fine hydroxyapatite crystallites were found to form at the interface after in vivo implantation into cortical bone.     

Numerical investigation of the effect of porous titanium femoral prosthesis on bone remodeling

Porous titanium is a promising orthopedic implant material. As a potential use in total hip replacement, the effect of a porous titanium femoral prosthesis on bone remodeling is investigated in this paper. The stress and strain fields of a post-operative femur with a hip replacement are calculated by applying the three-dimensional finite element method. The effect of the implant material on the bone remodeling is evaluated by analyzing the loss of bone density following a strain magnitude based bone remodeling theory. Different implant materials, including currently used solid cobalt–chrome and solid titanium, potential porous titanium with different porosities, are considered in this study. This investigation confirms that bone loss around the implant strongly depends on the value of the elastic modulus of the prosthesis. There will be a sharp drop of the volume of the bone with density loss if a cobalt–chrome implant is replaced by a porous titanium implant. The numerical results show that both of the bone volume with density loss and the bone density loss rate decrease linearly with the increase of the porosity. However, increasing porosity will reduce the strength of porous titanium. With regard to material design for porous titanium-based femoral prosthesis, stress analysis is required to meet the strength requirement.     

Experimental investigation on constitutive behavior of PVB under impact loading

During automotive related accidents, PVB plays an important role in both pedestrian and passenger protection as an interlayer of automotive windshield. In this paper, dynamic constitutive behavior of PVB material is thoroughly studied. Firstly, a set of dynamic compression impact experiments on PVB specimens using SHPB (Split Hopkinson Pressure Bar) method are conducted at strain rates from 700/s to 4500/s. Details of the constitutive response is analyzed based on the validation of experiment data. Stress-strain curve of PVB is then divided into two parts, i.e., “Compaction Stage” and “Hardening Stage”. Dislocations and entanglements among molecules are major reasons for the two-stage phenomena. Constitutive behaviors are different in low and high speed impacts, leading to three times more energy absorption ability of PVB in high speed impact scenario. Further, data fitting models based on both Mooney–Rivlin and Ogden Model are studied and then compared. Mooney–Rivlin Model is found to be more appropriate to describe PVB material. Moreover, PVB is proved to be a rate-dependent material with the failure strength intensify factor β ≈ 4. PVB material shows little viscoelasticity after comparison of the both models with and without the viscoelasticity part. Results offer critical experimental data, constitutive models and analysis of PVB material to further study of automotive crashworthiness and pedestrian/passenger protection.     

SEM in-situ investigation on failure of nanometallic film/substrate structures under three-point bending loading

Three-point bending tests on nanocrystalline Cu or Cu/Ni-film/Cu-substrate samples were conducted in-situ with scanning electron microscopy (SEM) observations. The SEM in-situ observations show undulation deformation of the surface of thin film, as the thin film fractures easily at the concave–convex points of deformation and multi-cracks appear on the surface of the thin film in a periodic fashion. The critical wavelength of undulation is calculated based on experimental observations, which are comparable with the theoretical predictions. For the Cu/Ni multi-layered films/substrate structures, the micro-cracking pattern depends on the interfacial strength between the film and the substrate, rather than the interfacial strength between the layers of films.