Gel Oxidation of Titanium and Effect of UV Irradiation on Precipitation of Hydroxyapatite from Simulated Body Fluid

Abstract

Sodium titanate gels on the surface of titanium metal have been formed using sodium hydroxide solution and oxidised at 400°-800°C. The reaction sequence for these processes with increasing temperature is Ti → sodium titanate gel → crystalline sodium titanate gel → porous (top) and dense (bottom) anatase → porous (top) and dense (bottom) rutile. These samples subsequently were soaked in simulated body fluid in order to study the precipitation of hydroxyapatite in the absence and presence of long UV radiation, which has not been investigated before. One sample showed greatly enhanced hydroxyapatite deposition, this being the one oxidised at 400°C, consisting of small amounts of crystalline sodium titanate and anatase, and subjected to UV irradiation. More generally, enhancement of hydroxyapatite precipitation is observed in the presence of anatase and/or sodium titanate; suppression of hydroxyapatite precipitation is observed in the presence of gels and rutile. However, UV light with anatase enhanced precipitation while UV light with rutile suppressed it. This is attributed to the morphological effect of the larger grain of rutile compared to the smaller anatase.