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A comparative study between hydroxyapatite coatings produced by two different techniques, plasma spray (PS) and pulsed-laser deposition (PLD) was carried out. Plasma spray is currently commercially used for coating dental and orthopaedical implant devices, and pulsed-laser deposition (or laser-ablation deposition) gave good results in the field of high critical temperature superconductive thin films, and is being applied to produce calcium phosphate coatings for biomedical purposes. X-ray diffraction was used to control the crystallinity of the coatings, scanning electron microscopy for the surface and cross-sectional morphology, and the pull test to determine the tensile strength of the coatings. This study reveals that the pulsed-laser deposition technique appears to be a very good candidate to replace the plasma spray in many biomedical applications, because it overcomes most of the drawbacks of the plasma spray.

Calcium phosphate coatings have been produced by pulsed laser deposition (PLD) at different water-vapour pressures. Rietveld refinement of X-ray diffraction (XRD) data allows us to determine that the structure of these coatings is apatitic with carbonate substitution for phosphate. The carbonate substitution decreases when the chamber pressure is raised, a fact that has been corroborated by Fourier transform-infrared (FT-IR) spectroscopy. Carbonate concentrations between 5 and 17 wt% have been calculated for the crystalline samples. Amorphous coatings are produced at the lowest and highest pressures due to the high carbonate concentration in the first case, and possibly to another type of substitution (Mg(2+), HPO(2-)4, P2O(4-)7) or the inherent kinetics of the PLD process, in the second case.

Resumen Los fosfatos calcicos apatíticos se utilizan como recubrimientos para mejorar la fijación de implantes ortopédicos y dentales. La técnica comercial para la producción de estos recubrimientos (plasmaspray) presenta problemas de adherencia y control de propiedades físico-químicas. En esta comunicación, se presenta la ablación láser como alternativa para solventar estos problemas. El sistema de ablación consiste en una cámara de vacío llena de vapor de agua hasta la presión deseada. El haz de un láser excímero de ArF se focaliza en un blanco de hidroxiapatito, depositándose el recubrimiento en un substrato paralelo al blanco mantenido a una cierta temperatura. Las propiedades físico-quími-cas del material se analizaron por espectroscopia infrarroja por transformada de Fourier (FT-IR), difracción de rayos X (XRD), microscopía electrónica de barrido (SEM) y espectroscopia de rayos X por dispersión de energías (EDX). Basándose en estos resultados, se escogieron dos tipos de recubrimientos para determinar su biocompatibilidad in vitro.Palabras clave: Ablación láser. Recubrimiento. Fosfato calcico. Implante. Production of calcium phosphate coatings by láser ablation for biomedical applications AbstractApatitic calcium phosphates are used as coatings to improve the fixation of orthopaedic and dental implants. The commercial technique to produce these coatings (plasm-spray) shows some problems of adherence and control of their physicochemical properties. In this communication láser ablation is presented as a solution to overeóme these problems. The ablation system consists in a vacuum chamber filled with water vapour up to the desired pressure. The láser beam of an ArF excimer láser is focused on a hydroxyapatite target, and the coating is deposited on a substrate parallel to the target maintained at certain temperature. The physicochemical properties of the material were analysed by Fourier transformed infrared spectroscopy (FT-IR) X ray diffraction (XRD), scanning electrón microscopy (SEM), and energy dispersive X ray spectroscopy (EDX). Taking into account these results, two types of coatings were choosen to asses their biocompatibility in vitro.

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