Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.
Ti-6Al-4V alloy is the most commonly used alloy for dental and orthopedic implants. In order to improve osseointegration, different surface modification methods are usually employed, including self-assembled monolayers (SAMs). This study presents an investigation of both active (electroassisted) and passive (adsorption) approaches for the modification of Ti-6Al-4V using alkylphosphonic acid. The monolayers were characterized by cyclic voltammetry, double-layer capacitance, contact angle measurements, X-ray photoelectron spectroscopy, polarization modulation infrared reflection adsorption spectroscopy, electrochemical impedance spectroscopy, and corrosion potentiodynamic polarization measurements. It is shown that the electrochemically assisted monolayers, which are assembled faster, exhibit better control over surface properties, a superior degree of order, and a somewhat higher packing density. The electrosorbed SAMs also exhibit better blockage of electron transfer across the interface and thus have better corrosion resistance.
Calcium phosphates are of great interest for biomedical applications such as bone tissue engineering, bone fillers, drug and gene delivery, and orthopedic and dental implant coating. Here, the first electrochemically driven coating of medical implants using hydroxyapatite (HAp) nanoparticles (NPs) as building blocks is reported. This uncommon combination offers a simple, straightforward, and economic process with well controllable, pure, single‐phase HAp. Crystalline, pure HAp NPs are formed by precipitation reaction. The HAp NPs are dispersed by either citrate or poly(acrylic acid) to form pH sensitive dispersion. Controllable and homogeneous coating of medical implants is accomplished by altering the pH on the surface upon applying either a constant potential or current. The process involves protonation of the carboxylic acid moieties, which causes the irreversible aggregation of the HAp NPs due to diminishing the repulsive forces between the particles. Deposition is further demonstrated on a commercial dental implant. Moreover, the adhesion of the coating satisfies FDA and international standard requirements. A porous interconnected network of bone‐like HAp layer is formed during soaking in a simulated body fluid for 30 d and is similar to bone generation, and it therefore holds promise for further in vivo testing.
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