This paper reviews the past, present, and future of the hydroxyapatite (HAp)-based biomaterials from the point of view of preparation of hard tissue replacement implants. Properties of the hard tissues are also described. The mechanical reliability of the pure HAp ceramics is low, therefore it cannot be used as artificial teeth or bones. For these reasons, various HAp-based composites have been fabricated, but only the HAp-coated titanium alloys have found wide application. Among the others, the microstructurally controlled HAp ceramics such as fibers/whiskers-reinforced HAp, fibrous HAp-reinforced polymers, or biomimetically fabricated HAp/collagen composites seem to be the most suitable ceramic materials for the future hard tissue replacement implants.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400042527

Processing and properties of hydroxyapatite-based biomaterials for use as hard tissue replacement implants

Copper toxicity, oxidative stress, and antioxidant nutrients.

Plasma-surface modification (PSM) is an effective and economical surface treatment technique for many materials and of growing interests in biomedical engineering This article reviews the various common plasma techniques and experimental methods as applied to biomedical materials research, such as plasma sputtering and etching, plasma implantation, plasma deposition, plasma polymerization, laser plasma deposition, plasma spraying, and so on The unique advantage of plasma modification is that the surface properties and biocompatibility can be enhanced selectively while the bulk attributes of the materials remain unchanged Existing materials can, thus, be used and needs for new classes of materials may be obviated thereby shortening the time to develop novel and better biomedical devices Recent work has spurred a number of very interesting applications in the biomedical field This review article concentrates upon the current status of these techniques, new applications, and achievements pertaining to biomedical materials research Examples described include hard tissue replacements, blood contacting prostheses, ophthalmic devices, and other products

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Plasma-surface modification of biomaterials

The clinical use of plasma-sprayed hydroxyapatite (HA) coatings on metal implants has aroused as many controversies as interests over the last decade. Although faster and stronger fixation and more bone growth have been revealed, the performance of HA-coated implants has been doubted. This article will initially address the fundamentals of the material selection, design, and processing of the HA coating and show how the coating microstructure and properties can be a good predictor of the expected behavior in the body. Further discussion will clarify the major concerns with the clinical use of HA coatings and introduce a comprehensive review concerning the outcomes experienced with respect to clinical practice over the past 5 years. A reflection on the results indicates that HA coatings can promote earlier and stronger fixation but exhibit a durability that can be related to the coating quality. Specific relationships between coating quality and clinical performance are being established as characterization methods disclose more information about the coating.

Material fundamentals and clinical performance of plasma-sprayed hydroxyapatite coatings: A review

In situ degradation of metal-alloy implants is undesirable for two reasons: the degradation process may decrease the structural integrity of the implant, and the release of degradation products may elicit an adverse biological reaction in the host Degradation may result from electrochemical dissolution phenomena, wear, or a synergistic combination of the two Electrochemical processes may include generalized corrosion, uniformly affecting the entire surface of the implant, and localized corrosion, affecting either regions of the device that are shielded from the tissue fluids (crevice corrosion) or seemingly random sites on the surface (pitting corrosion) Electrochemical and mechanical processes (for example, stress corrosion cracking, corrosion fatigue, and fretting corrosion) may interact, causing premature structural failure and accelerated release of metal particles and ions

The clinical importance of degradation of metal implants is evidenced by particulate corrosion and wear products in tissue surrounding the implant, which may ultimately result in a cascade of events leading to periprosthetic bone loss Furthermore, many authors have reported increased concentrations of local and systemic trace metal in association with metal implants1,4,5,9-11,14,18,25,26,28,29,47,49-55,58,71,72,75-77,87,90,108-110 There also is a low but finite prevalence of corrosion-related fracture of the implant

This review focuses on electrochemical corrosion phenomena in alloys used for orthopaedic implants A summary of basic electrochemistry is followed by a discussion of retrieval studies of the response of the implant to the host environment and the response of local tissue to implant corrosion products The systemic implications of the release of metal particles also are presented Finally, future directions in biomaterials research and development …

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Corrosion of metal orthopaedic implants.

Structure, solubility and bond strength of thin calcium phosphate coatings produced by ion beam sputter deposition.

Post-deposition heat treatments for ion beam sputter deposited calcium phosphate coatings

Concerns exist over the potential release of elevated levels of metal ions such as Ni and Be from Ni-Cr dental casting alloys, due to their susceptibility to accelerated corrosion. In this investigation, we evaluated the release of metal ions from four commercial Ni-Cr alloys, representing a range of compositions, in three-day cell culture tests. Metal ion release, as measured by atomic absorption spectroscopy, was correlated to changes in cellular morphology, viability, and proliferation. The results showed that the test alloys and their corrosion products did not affect cellular morphology or viabilities, but did decrease cellular proliferation. The types and amounts of metal ions released, which corresponded to the alloys' reported surface and corrosion properties, also correlated to observed decreases in cellular proliferation after 72 h. Neptune, which caused the smallest decrease in cellular proliferation as compared with control cells, released the lowest amount of corrosion products, due to its co...

Cellular Response to Metallic Ions Released from Nickel-Chromium Dental Alloys

Total hip prostheses combining cobalt and titanium alloys in direct physical contact are currently being used. The purpose of this paper was to investigate the possibility of an accelerated corrosion occurring due to the coupling of these alloys. Electrochemical corrosion studies based on mixed potential and protection potential theories were used to study the in vitro effects of coupling the titanium and cobalt alloys. Verification of these studies was made by direct coupling experiments. Macroscopic examination of' surface features of four retrieved total hip prostheses ranging from 0-6 years implantation were conducted. The electrochemical studies predicted coupled corrosion potentials of -0.22 V and low coupled corrosion rates of 0.02 microA/cm2. Direct coupling experiments verified these results. Cobalt-titanium interfaces on the implants were macroscopically examined, and no instances of extensive corrosion were found. Overall, the in vitro corrosion studies and the examination of retrieved prostheses predicted no exaggerated in vivo corrosion due to the coupling of these cobalt and titanium alloys.

Linda C. Lucas

Papers

Structure, solubility and bond strength of thin calcium phosphate coatings produced by ion beam sputter deposition.

Post-deposition heat treatments for ion beam sputter deposited calcium phosphate coatings

Cellular Response to Metallic Ions Released from Nickel-Chromium Dental Alloys

Investigations on the galvanic corrosion of multialloy total hip prostheses

Electrochemical corrosion analyses and characterization of surface-modified titanium