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Stem cells can become potent tools for the treatment of degenerative disorders such as heart failure, eye disease and osteoarthritis. Housing stem cells inside a hydrogel coating, directly deposited around them individually and in groups, may be an important solution to the problem of increasing stem cell viability and protection in cultivation. Such coatings can target regulatory proteins and genes for maintenance, differentiation and development into tissues. Already polymer coatings are being applied directly to protect insulin producing pancreatic islet cells in the hope of treating type I diabetes. Here, we review current emerging developments in adult mesenchymal stem cell nanocoating and microcoating techniques and assess their unique practical engineering, biological and potential clinical advantages. © 2012 Elsevier Ltd.

Objective. The purpose of this paper is to compare the differences in stress between Ti- 6Al- 4V and PS-ZrO 2 dental implant during clenching and whether these changes are clinically significant to limit the use of zirconia in oral implantology. Materials and methods. The model geometry was derived from position measurements taken from 28 diamond blade cut cross-sections of an average size human adult edentulous mandible and generated using a special sequencing method. Data on anatomical, structural, functional aspects and material properties were obtained from measurements and published data. Ti-6Al-4V and PS-ZrO 2 dental implants were modelled as cylindrical structure with a diameter of 3.26 mm and length of 12.00 mm was placed in the first molar region on the right hemimandible. Results. The analysis revealed an increase of 23% in the averaged tensile and compressive stress and an increase of 8% in the averaged Von Mises stress were recorded in the boneimplant interface when PS-ZrO 2 dental implant was used instead of Ti-6Al-4V dental implant. The results also revealed only relatively low levels of stresses were transferred from the implant to the surrounding cortical and cancellous bone, with the majority of the stresses transferred to the cortical bone. Conclusion. Even though high magnitudes of tensile, compressive and Von Mises stresses were recorded on the Ti-6Al-4V and PS-ZrO 2 dental implants and in the surrounding osseous structures, the stresses may not be clinically critical since the mechanical properties of the implant material and the cortical and cancellous bone could withstand stress magnitudes far greater than those recorded in this analysis. © 2012 Informa Healthcare.

The mechanical properties and adhesion behaviour of sol-gel derived hydroxyapatite (HA) nanocoatings on commercially pure (cp) titanium (Ti) and Ti6Al4V alloy have been determined and related to anodising treatment. The surface roughness, wetting and coating characteristics were examined using profilometry, contact angle, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Nano-indentation was used to determine the Young's modulus and hardness of the coatings, while microtensile tests were used to introduce controlled strains in the coatings through the cp Ti and TiAl6V4 alloy substrates, from which the strength, fracture toughness and adhesion behaviour could be ascertained based on multiple cracking and delamination events. The toughness of the HA coatings is found to be slightly lower to that of equivalent bulk pure HA ceramics. The substrate and the anodized layer thickness have the most influence on the interfacial adhesion of HA, with nanocoatings on Ti6Al4V exhibiting superior interfacial bonding in comparison to cp Ti. © 2010 Elsevier B.V.

Nanostructured materials are associated with a diversity of uses within the medical field, for instance, in drug-delivery systems, regenerative medicine, formation of surgical tools, medical devices, and diagnostic systems. It has long been established that porous bulk hydroxyapatite (HAp) cannot be used for load-bearing applications due to its unfavorable mechanical properties. As a result, HAp has been used instead as a coating in orthopedic surgery on metallic alloys, metals giving the support required. Of the metallic alloys used, titanium-based and cobalt chromium alloys are the preferred materials for these HAp coatings for orthopedic and maxillofacial implants (Figure 2.1).

Pharmaceutical drugs for the treatment of metabolic bone diseases lead to a number of side effects due to the their uncontrollable dispersion throughout the body.1 Therefore, many groups directed their research to develop devices that are targeted to specific organs or tissues and release the encapsulated drug in a highly regulated way.2-7 The development of completely resorbable bone-filling biomaterials delivering drugs would offer a therapeutic approach of drug release and bone augmentation in a simple one-step process.8-11 The biomaterials selected needs custom designs, to control the quantity and the duration of drug release and at the same time inducing desirable host cell responses and preventing bacterial infection.12-15 Current synthetic biomaterials produced as drug delivery microspheres due to production difficulties contain not very well designed interconnected pores and fail to fill these pertinent requirements. Turning directly to nature such as marine structures for inventive solutions can help to solve these problems due to their structure, chemistry and architecture and their unique designs.16-20 We demonstrate -for the first time- the potential of unique coral shells with specific microspherical structure and highly organised interconnected intra-pore designs to offer a number of desired functions for targeted delivery of Bisphosphonate (BP) (paminodrate) and an antibiotic (Gentamicin) for bone regeneration, repair and preventive antibacterial slow drug delivery. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The major advantage of hip resurfacing is the decreased amount of bone resection compared with a standard total hip replacement. Fracture of the femoral neck is the most common early complication and poor bone quality is a major risk factor. We undertook a prospective consecutive case control study examining the effect of bone mineral density changes in patients undergoing hip resurfacing surgery. A total of 423 patients were recruited with a mean age of 54 years (24 to 87). Recruitment for this study was dependent on pre-operative bilateral femoral bone mineral density results not being osteoporotic. The operated and non-operated hips were assessed. Bone mineral density studies were repeated over a two-year period. The results showed no significant deterioration in the bone mineral density in the superolateral region in the femoral neck, during that period. These findings were in the presence of a markedly increased level of physical activity, as measured by the short-form 36 health survey physical function score. ©2010 British Editorial Society of Bone and Joint Surgery.

Biomimetic approaches to the fabrication of advanced biomaterials and biostructures are used to address the shortcomings of existing scaffold designs that are traditionally biologically un-responsive throughout the regeneration process in situ and lack necessary versatility. Increasing focus is now being placed upon adaptating these advanced biomimetic scaffolds for human stem cells. In this chapter we describe new biomaterial led approaches to immobilization, maintenance, programming and promotion of desirable stem cell responses while regenerating clinically acceptable human tissues. We also describe efforts to enhance survivability of human cell transplantation inside protective devices. Biostructures are being designed into functional scaffolds that can adapt (evolve) to changing in situ environment during regeneration, regulate cell responses at nanostructured surfaces, as modules for self-assembling by the patient's own cells and as smart devices that possess tissue specific homing capabilities. © 2010 by Pan Stanford Publishing Pte. Ltd. All rights reserved.

Bisphosphonate is known to be a very active drug in the treatment of osteoporosis and bone regeneration. A new method has been developed, utilizing nuclear magnetic resonance spectroscopy to identify and measure the amount of bisphosphonate in solution. A standard reference with similar functional group to that of the bisphosphonate was chosen and applied in the experimentation. The results showed that the use of nuclear magnetic resonance spectroscopy ( 1H-NMR) in determining the solvent residues of various pharmaceutical drugs has proved to be effective. Unlike chromatography, it is possible to use a universal reference standard as an internal standard assayed by quantitative NMR. Using the same theory, this method is capable of both identifying and quantifying the bisphosphonate in various solutions. This paper is the first publication showing this unique measurement method, which can be used in a range of pharmaceutical and biomedical applications. © 2008 John Wiley & Sons, Ltd.

The mechanical properties of pure synthetic hydroxyapatite and hydroxyapatite-carbon nanotube composites were examined. Vickers microhardness and nanoindentation using a Berkovich tipped indenter were used to determine the hardness, fracture toughness and Young's modulus of the pure hydroxyapatite matrix and the composite materials. Microscopy showed that for the composites produced the carbon nanotubes were present as discrete clumps. These clumps induced a detrimental effect on the hardness of the materials, while the fracture toughness values were not affected. This would be undesirable in terms of using the material for biomedical implant applications. It should be noted that the carbon nanotubes used contained free graphite. As the properties of the composite materials studied were not greatly improved over the matrix, it is speculated that if the graphite phase were removed from the reagent, this could in-turn enhance the properties of the material. Copyright © 2008 American Scientific Publishers All rights reserved.

When producing implant materials, achievement of optimal bioactivity and biocompatibility are essential. Nanocoatings can provide an efficient cost effective way to alter the interactions of the implant material with its destined "host" environment. Nanocoatings of sol-gel derived carbonated hydroxyapatite (HAp) and zirconia were produced in this study. The surfaces were characterised by Fourier transform infrared spectroscopy (FTIR) and light microscopy. Cell adhesion, proliferation and viability, as well as expression of alkaline phosphatase (ALP is an indicator of bone formation) were assessed as indicators of biocompatibility. Our results have shown that sol-gel derived nano crystalline HAp acts as an ideal surface for implant coatings.

This study investigates the effect of specimen volume on the compressive strength of open cell brittle ceramics. A series of unconfined compression tests were carried out on specimens ranging in volume. The crushing strength and apparent stiffness were measured and these results are correlated with the volume of material stressed. It was found that as the volume of material tested decreased the strength decreased. © 2008 Trans Tech Publications.

Over the years, the use of hydroxyapatite as coatings for medical devices and drug-delivery systems has gone through a revolution - from being a rarity to being an absolute necessity. Without these coatings, many medical implants and devices would never reach their true potential in their intended applications, such as in the dental and orthopedic fields. Coatings of hydroxyapatite are often applied to metallic implants to alter their surface properties. The aim of this article is to present an evaluation of the published work regarding current research and applications and to review the methods used for the production of hydroxyapatite nanocoatings. © 2007 Future Medicine Ltd.

Orbital implants have been used for cosmesis following surgical removal of the eyeball, or enucleation, for over a century. Implant design has progressed significantly in recent years with the use of porous devices, with the theoretical advantages of reduced complications and improved cosmesis. However, in some cases the theoretical benefits have not fully translated into clinical results. In this article the use of orbital implants in enucleation, with a particular focus on the newer porous biomaterials that have gained prominence over the last 15 years, is reviewed. Specific factors identified as affecting the performance of porous orbital implants include the material used, pore size, and morphology. Mechanical factors have received little consideration in the past and may form a basis for the use of higher compliance porous materials in the future. Of the porous materials in use, current clinical evidence is not sufficient to suggest either that porous implants are superior to non-porous implants, or that one material is more suited to the application than another. Future developments in this field require randomized controlled clinical trials with extensive follow-up as complications may not become evident until over 5 years post-implantation. © 2007 Elsevier Inc. All rights reserved.

Hip resurfacing is proposed as an alternative to total hip replacement (THR) for treatment of osteoarthritis (OA), especially for younger, heavier and more active sufferers. There is however, concern with regards to the incidence of post operative femoral neck fractures. We have investigated, with finite element models, the changes in stress and strain in the femoral neck following hip resurfacing. We have included several different bone material property values representing normal, elderly, osteoarthritic and osteoporotic bone. We have also modelled two different hip implant orientations. We have shown that hip resurfacing may increase the magnitude of stress and strain in the femoral neck, especially in osteoporotic bone. We have also shown that the superolateral offset associated with the valgus orientation, not the valgus orientation itself, may be what reduces the stress and strain in the neck and leads to lower incidence of fracture.

Zirconia sol-gel-derived ceramic coatings have a variety of uses, due to their ease of production and ability to coat complex shapes. The sol-gel's nanocrystalline grain structure results in improved mechanical properties of the zirconia coating, which further aids their use in a variety of applications from thermal barrier coating to improved tribological properties on titanium substrates. Stabilised zirconia thin films were spin coated on anodised titanium substrates. The titanium was anodised in a dilute H3PO 4ZH2SO4 solution before spin coating with the zirconia sol gel. These films were then studied using secondary ion mass spectrometry (SIMS), to depth profile the elemental species through to the titanium substrate. In conjunction, scanning electron microscopy (SEM) and X-ray microanalysis were used to examine the craters formed by SIMS to gain an understanding of the diffusion gradient existing with the anodised titanium substrate and zirconia thin film. © Institute of Materials Engineering Australasia.

New methods for manufacturing alloy composites have been used to produce a number of wear parts for the mining industry. The use of composites incorporating white cast iron and steel permit brittle and wear resistant materials tobe used in applications where moderate impact conditions are encountered. Analysis of the alloy composite interfaces has provided an enhanced undertsnading of the bonding mechanisms between the white cast iron and the steel and has also permitted further improvements in the manufacturing techniques. Analysis methods used to examine the interfacial features include quantative x-ray mapping (QXRM) and electron beam backscattered diffraction (EMSD) mapping. Examples of successful field trials include mineral sands and wear parts for heavy earthmoving equipment.

This paper reports development of a production method to create a composite material that is biocompatible, which will have high mechanical strength and resilience, and be able to withstand exposure to the physiological environment. The chemical precipitation conditions necessary for the production of single-phase synthetic hydroxyapatite (HAp) and a HAp and carbon nanotube (CNT) composite material have been optimised. Neutron diffraction patterns collected before and after sintering show that the nanotubes have remained intact within the structure, while most of the remaining soot has burnt off. Small-angle neutron scattering, in conjunction with scanning electron microscopy (SEM), also shows preservation of the CNTs. Hot isostatically pressed samples showed excellent densification. Neutron diffraction data has enabled the positions of the hydroxide bonds to be determined, and shown that the addition of the CNTs has had no effect on the structural parameters of the HAp phase, with the exception of a slight reduction in the unit cell parameter a. © 2006 Elsevier B.V. All rights reserved.

Coatings offer the possibility of modifying the surface properties of surgical-grade materials to achieve improvements in performance, reliability and biocompatibility. Sol-gel-derived coatings demonstrate promise owing to their relative ease of production, ability to form a physically and chemically pure and uniform coating over complex geometric shapes and potential to deliver exceptional mechanical properties owing to their nanocrystalline structure. Other advantages unique to sol-gel include the production of a homogeneous material, since mixing takes place on the atomic scale, and its relatively low processing temperature avoids decomposition of the coating materials and limits the damage to metallic substrate materials as a result of exposure to elevated temperatures. A range of materials can be adapted easily for a number of biomedical and engineering applications. © 2006 Future Medicine Ltd.

This paper reports neutron diffraction data and its analysis that characterise a biocompatible hydroxyapatite composite material. The neutron data has elucidated the crystal structure, and enabled the positions of the hydrogen atoms to be determined. The data also shows the improvement of crystallinity during the heat treatment process. An extension of the work involved looking at a hydroxyapatite - carbon nanotube composite material, and neutron diffraction has shown that the retention of the carbon nanotubes in the composite material has been successful. The nanotubes have had no affect on the hydroxyapatite structure.

Titanium alloy has been used as a material for orthopaedic implants, however drawbacks still exist. Considerable efforts have been taken to modify the surface structure of the implant material and improve the biological performance. Previously we have demonstrated that biomaterials surface modification has a significant effect on the regulation of osteogenesis. We have investigated the behaviour of human osteoclasts on sol-gel coated carbonated hydroxyapatite on anodized titanium alloy. Osteoclasts cultured on the modified surface were able to attach and spread, exhibiting the characteristic peripheral brush border. Successful differentiation of the monocytes into osteoclasts and their attachment to the coated surface and the formation of resorption-like imprints indicated that carbonate hydroxyapatite (CHAP) coated titanium alloy play a significant role in regulating the functional activity of osteoclasts.

This study aims to characterize the structure and properties of crocodile bone to assess the potential for use in biomedical applications. Crocodile bone samples obtained from Thailand (Crocodylus siamensis) and Australia (Crocodylus porosus), being the tail and the tibia respectively, were treated to remove organic material and the inner spongy (trabecular) material. The dense cortical bone was used for comparative instrumental analyses. Specific comparisons were made against bovine cortical bone and pure synthetic hydroxyapatite. The material was then analyzed using simultaneous differential thermal analysis/thermogravimetric analysis (DTA/TGA), Fourier-Transform infrared spectroscopy (FTIR), and X-ray diffraction analysis (XRD). Imaging of full bone samples was also conducted using an environmental scanning electron microscopy (ESEM). The SEM provided valuable information through the imaging of samples, showing a marked increase in bone porosity for crocodile material when compared to bovine samples. The crystallinity and/or crystallite size of carbonated hydroxyapatite has been found to be lower than synthetic apatite, with the tibia being the least crystalline of the bone types studied. The crystallinity index (CI) is used as a measure of crystallite size and internal strain. The strain is affected by substitutions in the structure and these results provide a starting point for comparison of the resulting mechanical properties. There is a need for any biomaterial chosen for bone replacement to allow adequate osteointegration. Thus the study this far shows that crocodile bone is a very promising source of carbonated apatite for biomedical applications.

This paper reports development of a production method to create a composite material that is biocompatible, which will have high mechanical strength and resilience, and be able to withstand exposure to the physiological environment. The chemical precipitation conditions necessary for the production of single-phase synthetic hydroxyapatite (HAp) and a HAp and carbon nanotube (CNT)composite material have been optimised. Neutron diffraction patterns collected before and after sintering show that the nanotubes have remained intact within the structure, while most of the remaining soot has burnt off. Small-angle neutron scattering, in conjunction with scanning electron microscopy (SEM), also shows preservation of the CNTs. Hot isostatically pressed samples showed excellent densification. Neutron diffraction data has enabled the positions of the hydroxide bonds to be determined, and shown that the addition of the CNTs has had no effect on the structural parameters of the HAp phase, with the exception of a slight reduction in the unit cell parameter a.

Poor cell adhesion to orthopaedic and dental implants results in implant failure. Establishing and maintaining mature bone at the bone/device interface is critical to the long-term success of the prostheses. Considerable effort has been devoted to alter the surface characteristics of these biomaterials in order to improve the initial interlocking of device and skeleton in the non-cemented joint prosthesis. Previously we demonstrated that surface chemistry modification of bioceramics induced osteogenesis. In the present work, we investigate the effect of surface chemistry modification of titanium alloy (Ti-6Al-4V) with alkoxide-derived carbonate hydroxyapatite (CHAp) using sol-gel coating methods on human bone derived cell (HBDC) behaviour. Western blotting demonstrated that sol gel coating of Ti-6Al-4V with CHAp upregulated the expression of key signalling protein Shc isoforms (p46, p52, p66) and phosphorylated Erk1/2. CHAp-modification of Ti-6Al-4V is associated with signal transduction pathways involving the key signalling protein She and ERK1/2 which may lead to enhanced gene expression of extracellular matrix proteins at the skeletal tissue/device interface.

The distribution of about twenty inorganic elements was traced in the skeletons of black corals of the Antipathes sallx species. Electron microprobe and PIXE mappings revealed the peculiar structure of this material, composed of the large cells (arranged in annual rings), surrounded by thin layers with an elevated level of iodine (up to 5%). Our current knowledge of the chemical composition of these corals' skeleton is not complete. Essentially the organic skeleton is saturated with inorganic elements and several of these could be commercially important. In fact, they have never been investigated for biomedical applications. In this preliminary current work, black corals from the Antipathes salix species were studied with the aim of detecting the inorganic components of their matrix and their suitability as biomedical materials.

There have been a number f new processes developed that allow the joining of very dissimilar materials such as titanium alloys, wear resistant white irons, cast irons and ceramic materials to ferrous (mild steel) and non-ferrous (aluminium) alloys. These new processes have allowed the development of more complex composite shapes to be produced. However, with any new process development, an undertsnating of the mechanism of bonding is required. through the use of x-ray mapping (XRM), chemical phase imaging as well as electron back scattered diffraction (EBSD) analsysis, very useful information on the mass transport across the interface as well as phase segregation, texture variations and phase distribution within the bond interface can be obtained. results from this investigation on a number of bonded materials are presented and the importance of XRM and EBSD in providing a better understanding of the physical and chemical processes involved in metallurgical bonding/welding of dissimilar materials discussed.

Background: Until recently, very few papers have been published concerning the development, analysis and experimental verification of three-dimensional, finite element modelling of the human adult edentulous mandible. The purpose of this study was to improve the method of modelling by using computer-aided engineering (CAE) and computer-aided design (CAD) methods and to utilize the model in analyzing maxillofacial problems. Methods: The model geometry was derived from position measurements taken from 28 diamond blade cut cross-sections of an average size human adult edentulous mandible and generated using a special sequencing method. Data on anatomical, structural, functional aspects and material properties were obtained from measurements and published data. The materials were idealized as transversely isotropic. The complete model consisted of 258 solid elements and 1635 nodes. Results: The model was solved for displacements and stresses during clenching. In general, the observed displacement and stresses (tensile and compressive) were highest around the condylar region. Compressive stress was also observed around the premolar and molar bite points. Conclusion: This investigation has shown that the use of computer-aided modelling in conjunction with the finite element analysis could be effectively utilized in biomechanical analysis of the mandible. It could help to investigate many functional problems and could reduce the time of extensive experimentations.

The morphology, adhesion and tribological properties of the zirconia sol-gel coatings on phosphate treated, anodized and un-treated titanium surfaces were investigated. The anodization of titanium involves the formation of a thin, compact, oxide layer, which improves the wettability for further coating. This process involves the conversion of the rutile structure of the original titanium oxide into a mostly crystalline anatase structure. The samples were anodized in sulphuric and phosphoric acid at varying concentrations. The samples were anodized at differing currents and differing time periods ranging from 10 to 30 minutes. Phosphate adsorption treatment involves soaking samples in 10% H3PO4 solution for 10 minutes. These samples were spin coated with zirconia, yielding 100 nm thick films. The nanocoatings were prepared by alkoxide sol-gel chemistry, using techniques and protocols developed in an earlier work and were examined with x-ray diffraction, and scanning electron microscopy. Interfacial and adhesion properties were measured using a micromechanical tensile test. The tribological properties were investigated using an Orthopod machine, with commercial grade ultra-high molecular weight polyethylene (UHMWPE) pins (3/8 inch diameter) that can articulate in number of different combinations against opposing coated and control specimens. The UHMWPE pins were used in a bovine serum environment. The amount of the wear was measured gravimetrically and wear features were observed using SEM.

Overall, the benefits of advanced ceramic materials in biomedical applications have been universally appreciated, specifically, in terms of their strength, biocompatibility and wear resistance. However, the amount of supporting data is not large and the continuous development of new methods is pertinent for better understanding of the microstructureproperties relationship and, in general, for obtaining new directives for their further improvement. This paper gives an overview of some of the more innovative applications of bioceramics in medicine.

An improved understanding of the interactions at the anoscale level between the bioceramics in medical implants and the hard or soft tissues in the human body could contribute significantly to the design of new-generation prostheses and postoperative patient management strategies. Overall the benefits of advanced ceramic materials in biomedical applications have been universally accepted, specifically in terms of their strength, biocompatibility, hydrophilicity and wear resistance in articulating joints. The continuous development of new-generation impalnts untilising nanocoatings with novel nanosensors and devices is leaf=ding to better compatibility with human tissue and improved well-being and longevity for patients. This article gives a short oevrview odf bioceramics and reexamines key issues of concern for processing and applying nanosensors as biomaterials.

Current bone graft materials are mainly produced from coralline hydroxyapatite (HAp). Due to the nature of conversion process, commercial coralline HAp has retained coral or CaCO3 and the structure possesses nanopores within the inter pore trabeculae resulting in high dissolution rates. Under certain conditions these features reduce durability and strength respectively and are not utilised where high structural strength is required. To overcome these limitations, a new-patented coral double-conversion technique has been developed. The current technique involves two-stage application route where in the first stage complete conversion of coral to pure HAp is achieved. In the second stage a sol-gel derived HAp nanocoating is directly applied to cover the micro and nano-pores within the intra pore material, whilst maintaining the large pores. Biaxial strength was improved due to this unique double treatment. This application is expected to result in enhanced durability and longevity due to monophasic hydroxyapatite structure and strength in the physiological environment. It is anticipated that this new material can be applied to load bearing bone graft applications where high strength requirements are pertinent.

Hydroxyapatite powders [Ca10(PO4)6(OH)2] (HAp) were produced via sol-gel method. The thermal crystallization behavior was studied by means of differential thermal analysis, differential scanning calorimetry (DSC), mass spectrometry (MS) and scanning electron microscopy. A variable heating rate approach was used to calculate the activation energy of crystallization of hydroxyapatite from amorphous precursor (235 kJ/mol). The plate-like morphology observed in the hydroxyapatite precursor at 150 °C resulted in plate-like hydroxyapatite. © 2002 Published by Elsevier Science B.V.

Recent advances in the production and use of natural bioceramics for applications in hard and soft tissue replacement are discussed. The synthesis of complex inorganic forms, which are based on natural structures that can mimic natural scaffold, upon which the cells are seeded, offers an exciting range of avenues for the construction of a new generation bone analogs for tissue engineering. The use of natural and synthetic calcium phosphate bioceramics as bone grafts in orthopaedics and dentistry is considered. Issues affecting the use of different materials in vivo are outlined, of particular importance are osteoconductivity (ability to support tissue ingrowth and bone formation) and osteogenicity (formation of bone from cells within a bone graft). A variety of other natural alternatives including sol-gel coated coralline apatite are evaluated, and other key success factors (strength, longevity and stability) are reviewed. Several treatments for improving performance are outlined, and speculation on future advances, including combination of traditional bioceramic implants with more recent advances in stem cell research is made. © 2003 Elsevier Ltd. All rights reserved.

Little is known about the wear of zirconia-zirconia bearing systems for total joint replacements. In this study zirconia-zirconia specimens were run on a simulator with water lubrication. After catastrophic failure of the bearings, the lubricating fluid was filtered and the wear debris examined. The debris particles were larger than would be expected and exhibited a monoclinic structure. The wear surface showed signs of extensive delamination consistent with failure of the bearing surfaces. Water lubrication under hip simulator conditions results in rapid failure of zirconia surfaces. However, wear studies of zirconia-zirconia hip designs with serum lubrication to over twenty million cycles demonstrated little if any wear change of the bearing surfaces.

A new species, which was found and cloned under field and laboratory condition at the Red Sea, was used in the present study. Specific high density Red Sea coral was used for analysis. A modified and improved hydrothermal conversion process was used to convert the hydrocorals from calcium carbonate to HAp. The effects of the hydrothermal conversion on the pore size and the surface morphology of HAp structure have been studied using scanning electron microscopy (SEM) and atomic force microscopy (AFM). After the hydrothermal conversions the samples were further dip-coated via a new alkoxide sol-gel method and were examined to determine the surface parameters and morphology. It is anticipated that following the hydrothermal conversion and processing this new high density calcium phosphate coralline material can be used as a new bioceramic material in medical applications.

In hip simulation studies, zirconia fails in water and saline but survive in calf serum environments at specific protein concentrations. Until now there has not been a theoretical basis for explaining this behaviour. Here we present for the first time a body of microstructural evidences based on Raman microprobe spectroscopy, which clarify the origin of this different behaviour. Microscopic maps of residual stresses and localised phase transformation from tetragonal to monoclinic are presented. These findings provide the theoretical basis for better understanding wear phenomena in zirconia and to establish the structural and micromechanical reasons for their superior behavior in physiologic environments.