AFM Observations and Composition Analyses of the Top Surfaces of HA Implants

抄録

From the perspective of excellent biocompatibility and osteoconductivity of hydroxyapatite (HA), the frequency of use of HA implants has been steadily increasing in recent years. But the coating layer of certain commercialized HA implants may not be primarily composed of HA, and it may be assumed that the coating layers, contained some HA components, are automatically categorized to the HA implant. The characteristics of the implant to vital tissues are attributable to the properties of the surface components of the implant. Scanning electron microscope (SEM) observations and X-ray diffraction (XRD) analyses of the HA coating have been performed previously, but SEM has some difficulties in showing clear images of the HA crystal due to the influence of coating conditions etc., and the results obtained from XRD are not limited to the surface where contact with vital tissues, but also exhibit the inner components of the coating layer. Therefore, it might be assumed that reports limited to the top surface of the HA coating have still not been published. In this study, AFM observations, and XPS and micro-XRD analyses were performed on the top surface of five commercially available HA implants. AFM results showed that HA crystals were clearly observed on the surface of two samples. XPS and micro-XRD analyses exhibited that HA was detected in all the samples, but other substances including Ti, TiO₂, CaTiO₃, etc., were also confirmed in several samples. These results showed that HA was present on the top surface of all HA implants, and also indicated that all implants might exhibit some sort of biocompatibility and osteoconductivity due to their bioactive natures caused by HA.