A scanning electron microscopy study of the interface between ceramics and bone

By use of scanning electron microscopy (SEM), together with energy dispersive chemical analysis, a study has been made of the comparison of an in vitro method of assessing interface reactions between bone and ceramic implants with the naturally occurring changes seen in the rat ear model. Interface reactions between bone and two ceramic materials were examined following 4 wk in culture and 4 wk implantation. In both cases a gradual chemical change occurred at the calcium silicate surface during the fibrous growth onto the ceramic material. Gradual mineralization of the connective fibres was found at the interface of the calcium silicate material, whereas, in the case of alumina ceramic a connective fibrous bond had formed with no associated chemical change at the ceramic surface.     

金红石型钛白粉表面包覆氧化铝的形态及机理

探讨了以H2SO4和CH2OHCH2Cl为酸解介质时,氯化法金红石型钛白粉表面包铝的行为及形态特征。利用正交实验研究了包膜过程中,熟化pH、熟化时间以及温度对包铝钛白粉白度的影响。氯化法金红石型钛白粉浆在pH为10时,Zeta电位最大,在水中达到最佳分散,利用H2OHCH2Cl作为酸解介质时,浆液中的均相成核得到显著抑制,钛白粉表面的包膜质量得到明显改善。以稀硫酸作为酸解介质时,随熟化温度升高和熟化时间的延长,钛白粉包覆效果明显改善,白度值明显升高。     

Hydrogen Production by Steam Reforming of Ethanol over Nickel Catalysts Supported on Sol Gel Made Alumina: Influence of Calcination Temperature on Supports

Selecting a proper support in the catalyst system plays an important role in hydrogen production via ethanol steam reforming. In this study, sol gel made alumina supports prepared for nickel (Ni) catalysts were calcined at different temperatures. A series of (Ni/Al_S.G.) catalysts were synthesized by an impregnation procedure. The influence of varying the calcination temperature of the sol gel made supports on catalyst activity was tested in ethanol reforming reaction. The characteristics of the sol gel alumina supports and Ni catalysts were affected by the calcination temperature of the supports. The structure of the sol gel made alumina supports was transformed in the order of γ → (γ + θ) → θ-alumina as the calcination temperature of the supports increased from 600 °C to 1000 °C. Both hydrogen yield and ethanol conversion presented a volcano-shaped behavior with maximum values of 4.3 mol/mol ethanol fed and 99.5%, respectively. The optimum values were exhibited over Ni/Al_S.G800 (Ni catalyst supported on sol gel made alumina calcined at 800 °C). The high performance of the Ni/Al_S.G800 catalyst may be attributed to the strong interaction of Ni species and sol gel made alumina which lead to high nickel dispersion and small particle size.     

The reliability of modern alumina bearings in total hip arthroplasty—Update to a 2006 report

Ceramic components׳ clinical fractures in total hip arthroplasty (THA) are a rare but, nonetheless, serious complication. As a result of continued improvements in ceramic material quality, manufacturing methods, and implant design made over the last 30 years, the incidence of such failures has been drastically reduced. In this report, the frequency of these ceramic components׳ clinical failures in THA will be examined. In addition, some information regarding the contribution that can be made by the surgeon to enhance the reliability of ceramic components will also be presented. In order to get a broad view, the largest supplier of these components, CeramTec Medical Products (Plochingen, Germany), was contacted, and they agreed to share their most recent data. In the year 2000, the largest supplier of alumina–ceramic bearings for orthopedic applications (CeramTec GmbH, Plochingen, Germany) began a rigorous program of collecting clinical fracture data for all of its ceramic components. The clinical fracture data for the period of January 2000–June 2013 are reported here, with a review of the material properties, historical component fracture trends, and relative risk of fracture associated with alumina THA bearings. The data reported is divided into two separate groups. The first one is the incidence of clinical fracture of the Biolox^® forte material. This is their original material developed in the 1970s and is still available today and optimized over the years. The overall clinical fracture rate of these alumina components was 0.021%, or 21 in 100,000, during the January 2000–June 2013 time period. The second group is composed of components manufactured from their Alumina Matrix Composite, Biolox^® delta. The overall clinical fracture rate for these components is 0.0001% or 1 in 100,000. Almost 80% of these alumina bearing failures occurred within 36 months following surgery. Using the latest material and increasing femoral head diameter were associated with a substantially reduced risk of fracture. Alumina bearings used in modern THA implants are safe and reliable, with a very low risk of failure. Improvements in the materials, developments in the manufacturing, the introduction of the Alumina Matrix Composite, and the trend to utilize larger-diameter ball heads are likely to continue to reduce the concerns that have been in the mind of surgeons using ceramics in THA.     

Biological Activation of Inert Ceramics: Recent Advances Using Tailored Self-Assembled Monolayers on Implant Ceramic Surfaces

High-strength ceramics as materials for medical implants have a long, research-intensive history. Yet, especially on applications where the ceramic components are in direct contact with the surrounding tissue, an unresolved issue is its inherent property of biological inertness. To combat this, several strategies have been investigated over the last couple of years. One promising approach investigates the technique of Self-Assembled Monolayers (SAM) and subsequent chemical functionalization to create a biologically active tissue-facing surface layer. Implementation of this would have a beneficial impact on several fields in modern implant medicine such as hip and knee arthroplasty, dental applications and related fields. This review aims to give a summarizing overview of the latest advances in this recently emerging field, along with thorough introductions of the underlying mechanism of SAMs and surface cell attachment mechanics on the cell side.     

烧结温度对牙科氧化锆增韧氧化铝陶瓷力学性能及微观结构的影响

目的 探讨烧结温度对牙科氧化锆增韧氧化铝（ZTA)陶瓷的力学性能及微观结构的影响。方法 在不同烧结温度下（1100℃、1200℃、1350℃、1450℃、1550℃）制备牙科ZTA陶瓷,在烧结完成后测定不同烧结温度下ZTA陶瓷硬度、脆性、线收缩率,并观察微观结构的变化。〖HTH〗结果 随着烧结温度的升高,ZTA陶瓷的硬度、脆性及线收缩率逐渐升高,且比较各温度间ZTA陶瓷的硬度、脆性及线收缩率,差异均有统计学意义（P＜0.05）。 结论 不同烧结温度对ZTA陶瓷脆性、硬度、线收缩率及微观结构的影响不同,当烧结温度在1350℃的条件下时,ZTA陶瓷的上述性能处于最佳状态。     

Ceramic Biomaterial Pores Stereology Analysis by the Use of Microtomography

The main aim of this study was to analyze microtomographic data to determine the geometric dimensions of a ceramic porous material’s internal structure. Samples of a porous corundum biomaterial were the research material. The samples were prepared by chemical foaming and were measured using an X-ray scanner. In the next stage, 3D images of the samples were generated and analyzed using Thermo Scientific Avizo software. The analysis enabled the isolation of individual pores. Then, the parameters characterizing the pore geometry and the porosity of the samples were calculated. The last part of the research consisted of verifying the developed method by comparing the obtained results with the parameters obtained from the microscopic examinations of the biomaterial. The comparison of the results confirmed the correctness of the developed method. The developed methodology can be used to analyze biomaterial samples to assess the geometric dimensions of biomaterial pores.     

Zirconia–Alumina Composites Obtained by Centrifugal Slip Casting as Attractive Sustainable Material for Application in Construction

This paper focuses on the possibility of adapting the centrifugal slip casting method to obtain zirconia–alumina composite materials in the form of finished tube-shaped products. These types of products, due to their unique properties, can be utilised, for example, in the transport of aggressive substances, even in extreme temperatures or corrosive conditions. The study reports on the two series of zirconia–alumina composites differing in the content of ZrO₂—2.5 and 25 vol%. The fabricated and sintered materials were characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD) and stereological analysis. Moreover, a life cycle assessment (LCA) was provided in accordance with the requirements of the ISO 14044 and EN 15805 standards. The obtained data clearly show that the centrifugal slip casting method allows obtaining samples with high density and extremely uniform distribution of the ZrO₂ phase in the alumina matrix. The stereological analysis results proved also that the addition of ZrO₂ is effective in reducing the growth of Al₂O₃ grains during the sintering process. The phase analysis carried out by means of XRD showed that during the sintering process, in the case of composites with a lower ZrO₂ content (2.5 vol%), the monoclinic to tetragonal transformation of ZrO₂ was total, while for samples containing 25 vol% ZrO₂, the monoclinic phase remained in a small amount in the final product.     

True Strength of Ceramic Fiber Bundles: Experiments and Simulations

A study on the strength of ceramic fiber bundles based on experimental and computational procedures is presented. Tests were performed on single filaments and bundles composed of two fibers with different nominal fiber counts. A method based on fiber rupture signals was developed to estimate the amount of filament rupture during the test. Through this method, the fiber bundle true strength was determined and its variation with the initial fiber count observed. By using different load-sharing models and the single filament data as input parameter, simulations were also developed to verify this behavior. Through different approaches between experiments and simulations, it was noted that the fiber bundle true strength increased with the fiber count. Moreover, a variation of the fibers’ final proportion in the bundles relative to the initial amount was verified in both approaches. Finally, discussions on the influence of different load-sharing models on the results are presented.     

Simulation of clinical fractures for three different all‐ceramic crowns

Comparison of fracture strength and fracture modes of different all‐ceramic crown systems is not straightforward. Established methods for reliable testing of all‐ceramic crowns are not currently available. Published in‐vitro tests rarely simulate clinical failure modes and are therefore unsuited to distinguish between the materials. The in‐vivo trials usually lack assessment of failure modes. Fractographic analyses show that clinical crowns usually fail from cracks initiating in the cervical margins, whereas in‐vitro specimens fail from contact damage at the occlusal loading point. The aim of this study was to compare three all‐ceramic systems using a clinically relevant test method that is able to simulate clinical failure modes. Ten incisor crowns of three types of all‐ceramic systems were exposed to soft loading until fracture. The initiation and propagation of cracks in these crowns were compared with those of a reference group of crowns that failed during clinical use. All crowns fractured in a manner similar to fracture of the clinical reference crowns. The zirconia crowns fractured at statistically significantly higher loads than alumina and glass‐ceramic crowns. Fracture initiation was in the core material, cervically in the approximal areas.