Material removal during the sliding of hydroxyapatite against UHMWPE

Article type: Research Article

Authors: Mazeau, G. | Czernuszka, J.T.^;

Affiliations: La Formation d'Ingenieurs de l'Université Paris‐Sud‐Orsay, Plateau du Mallon, Bat. 620, 91140 Orsay, France | Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK

Note: [] Corresponding author.

Abstract: Hydroxyapatite has been rubbed against ultra‐high‐molecular‐weight‐polyethylene (UHMWPE) under calcium‐containg aqueous solutions. Further, hardness tests were carried out in air and in calcium‐containing solutions whose pH ranged from pH 5 to pH 9. Hardness was found to vary with pH with a peak at around pH 7, i.e. – a chemomechanical effect was observed. Wear tests consisted in sliding hydroxyapatite samples against a UHMWPE disk for eight hours when lubricated by the same solutions as those used for the hardness tests. Volume loss, pH and calcium concentration were measured for up to 8 hours of sliding. Linking wear tests results with hardness results and supersaturation levels, it was concluded that two wear mechanisms occurred. A chemical mechanism depending on supersaturation occurred at the early stages of sliding. The wear rate was essentially independent of hardness during this stage. After a few hours, depending on the supersaturation of the lubricant, the chemical mechanism turned into a chemomechanical mechanism dependant on hardness.

Keywords: Hydroxyapatite, wear, polyethylene, chemomechanical effects, chemical wear

Journal: Bio-Medical Materials and Engineering, vol. 11, no. 4, pp. 283-392, 2001