Degradation potential of plasma-sprayed hydroxyapatite-coated titanium implants

Area of Science:

• Biomaterials Science
• Materials Chemistry
• Orthopedic Research

Background:

• Hydroxyapatite (HAP) coatings are widely used in orthopedic devices for enhanced osseointegration.
• Understanding the dissolution behavior of HAP coatings is crucial for predicting their long-term performance and biocompatibility.
• Variability in HAP coating properties can influence their interaction with physiological environments.

Purpose of the Study:

• To develop and apply an analytical method for assessing the dissolution characteristics of plasma-sprayed hydroxyapatite (HAP) coatings.
• To compare the dissolution behavior of commercially available HAP coatings used in orthopedic applications.

Main Methods:

• Preconditioning of HAP-coated titanium implants in a 0.15 mol L-1 sodium chloride solution at 37°C.
• Dissolution testing using the dual constant composition (DCC) method under controlled undersaturation.
• Analysis of coating crystallinity and composition using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR).

Main Results:

• Significant differences in dissolution rates, up to a factor of 5, were observed among various commercial HAP coatings.
• No changes in crystallinity or chemical composition of the HAP coatings were detected before and after dissolution treatment via XRD and FTIR.
• The aqueous environment elicited distinct dissolution responses from HAP coatings sourced from different manufacturers.

Conclusions:

• Plasma-sprayed HAP coatings from different commercial sources exhibit markedly different dissolution behaviors in aqueous environments.
• Despite similar bulk properties (crystallinity, composition), extrinsic factors influence HAP coating dissolution rates.
• Further research is required to correlate these in vitro dissolution findings with in vivo performance in orthopedic implants.