Deposition of apatitic calcium phosphate coatings by Laser ablation

Abstract

Apatitic calcium phosphates are currently used as coatings to improve fixation of cementless titanium based implant devices. The most commonly used technique to produce these coatings is the plasma spray. This method presents some disadvantages, such as the poor control of the physico-chemical properties of the coatings or their low mechanical performances, affecting the further stability in-vivo of the material.More recently, Laser Ablation (LA), has been successfully applied to produce calcium phosphate coatings of different composition, structure and crystallinity. The purpose of this study is to show the possibilities of the apatitic calcium phosphate coatings produced by LA, as well as their biocompatibility.The LA system consisted basically in a vacuum chamber, evacuated up to 10−6 mbar, then filled with water vapour up to the desired processing pressure. The laser (ArF excimer laser, λ = 193 nm) was focused onto a hydroxyapatite (HA) sintered pellet, and the substrate (c-silicon, corning glass, Ti6Al4V alloy and pure Ti) was placed in front of the target, on a temperature controlled substrate holder.The influence of the deposition parameters on the physico-chemical properties of the coatings has been object of a systematic study. Different analytical techniques were applied to characterize the coated samples, including Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). Also ellipsometry and profilometry were used to evaluate the coatings thickness; and pull test for the tensile strength.The results obtained show that most of the physico-chemical properties of the coatings can be easily tailored by tuning the processing parameters. Moreover, excellent adhesion, combined with a good crystallinity and stoichiometry of calcium phosphate coatings can be achieved at relatively low temperatures.After the systematic study of the influence of the processing parameters on the physico-chemical properties of the coatings, two different types were selected to assess their biocompatibility in-vitro by studying the attachment and proliferation of MG63 osteoblastlike cells on them. The selected materials showed a very good biocompatibility.The results of the complete study reveal that this kind of coatings are suitable to be applied on titanium based implant devices. appearing as a good candidate to solve the drawbacks of the methods actually used for commercial purposes.Apatitic calcium phosphates are currently used as coatings to improve fixation of cementless titanium based implant devices. The most commonly used technique to produce these coatings is the plasma spray. This method presents some disadvantages, such as the poor control of the physico-chemical properties of the coatings or their low mechanical performances, affecting the further stability in-vivo of the material.More recently, Laser Ablation (LA), has been successfully applied to produce calcium phosphate coatings of different composition, structure and crystallinity. The purpose of this study is to show the possibilities of the apatitic calcium phosphate coatings produced by LA, as well as their biocompatibility.The LA system consisted basically in a vacuum chamber, evacuated up to 10−6 mbar, then filled with water vapour up to the desired processing pressure. The laser (ArF excimer laser, λ = 193 nm) was focused onto a hydroxyapatite (HA) sintered pellet, and the substrate (c-silicon, corning glass, Ti6...