Hydroxyapatite Waterjet Treatment of Implants

Author:  Alade, Weber, Sadasivam, Arola, Milidantri
Source:  The Shot Peener magazine, Vol 20 / Issue 3, Summer 2006
Doc ID:  2006021
Year of Publication:  2006
Abstract:  
INTRODUCTION Hydroxyapatite (HA) coatings are applied to the surface of dental and orthopaedic implants to enhance the development of a surface topography and surface chemistry that supports early osseointegration and mechanical interlock. Deposition of HA coatings is most often achieved via thermal plasma spray, which results in a porous coating of embedded HA particles. While porous coatings are considered essential for stable primary fixation, the fatigue strength of these coated devices is often less than that of the metal in wrought form [1]. Additional complications arise due to delamination and fracture of the coating from the substrate. The reduction in fatigue strength is attributed to stress concentrations posed by the porous surface topography and through microstructural changes that result from the deposition process. Abrasive Waterjet Peening (AWJ) is a newly developed method of surface treatment that has been proposed for orthopedic applications [2]. Studies on AWJ peening of metals have shown that the process is capable of introducing a surface texture that supports mechanical interlock, results in compressive residual stress and that particles can be impregnated within a substrate to provide the desired surface chemistry [3-5]. While promising, treatments had not been performed using HA particles. Based on the difference in hardness of HA with respect to other more common mineral and ceramic abrasives, the ability to impart residual stresses and surface characteristics favorable to orthopedic applications has remained unknown. Thus a small exploratory study was performed to confirm that the waterjet treatment with HA particles is feasible. The primary objectives of the investigation were to confirm that HA particles can be introduced within the treated surfaces and that an increase in fatigue strength can be achieved.