Particle attrition of alpha-tricalcium phosphate: effect on mechanical, handling, and injectability properties of calcium phosphate cements.

Calcium phosphate bone cements are currently used in a range of applications; however, their low compressive strength and brittle failure mechanics have limited their widespread application. The aim of this study was to improve the mechanical performance of the calcium phosphate cement by means of particle reduction of the powder components involved. alpha-Tricalcium phosphate (alpha-TCP) powder was produced and subsequently reacted with water to form a calcium-deficient hydroxyapatite in the form of a biocompatible and resorbable cement. It was postulated that the reduction of the alpha-TCP particle size would result in a faster-setting reaction and stronger cement. Three milling techniques were explored and their methods optimized. The techniques included the traditional ball-milling technique and two newer techniques, namely cryogenic and planetary milling. Particle size analysis through laser diffraction and scanning electron microscopy was conducted. Compressive strength, setting times and injectability characteristics of the curing cement were determined. It was observed that all three techniques were efficient methods of particle reduction and the mechanical, setting and injectability properties were significantly improved by the reduction in particle size of the alpha-TCP powder. However, agglomerations of alpha-tricalcium phosphate resulted in a reduction in compressive strength and injectability after prolonged milling periods, irrespective of milling technique.