Hydroxyapatite based machinable bioceramic: An in depth investigation on drilling parameters and bioactivity

The use of Hydroxyapatite (HAp) bioceramics as restorative implants is widely known. However, machining processes are still a basic requirement to give a near net shape to those implants for ensuring dimensional and geometrical accuracy. In this context, optimizing the machining parameters is an important factor to understand the machinability of the materials. In the present study a method has been optimized to produce drillable composite of HAp Yttrium Phosphate (YP). The phosphates are used in varying ratio for a comparative study on the effect of phase analysis, flexural strength, hardness, machining (drilling) parameters, bioactivity and biocompatibility. Drilling is done with a conventional radial drilling machine aided with dynamometer with high speed steel (HSS) and solid carbide (SC) drills. The effect of variation in drilling parameters (cutting speed and feed), cutting tool, batch composition on torque and thrust force are studied. It is observed that the thrust force and torque varies greatly with the increase in the speed, feed and YP content in the composite. Bioactivity study is done in simulated body fluid (SBF) up to 28 days. The growth of the bone like apatite has become denser with the increase in the number of days for all the composition of the composites. Biocompatibility study was done using MTT assay technique.