Thin films of calcium phosphate and titanium dioxide by a sol-gel route: anew method for coating medical implants

Titanium is a commonly used biomaterial for dental and orthopaedic applicat ions. To increase its ability to bond with bone, some attempts were made to coat its surface with calcium phosphate (CaP). This paper describes a new type of coating. Instead of a pure CaP layer, a mixing of titanium dioxide (TiO2) and CaP is fabricated and deposited as a coating. These layers are d eposited by a sol-gel route on pure titanium substrates using various pre-t reatments. The method consists of mixing a solution of tetrabutyl ortho-tit anate or a sol of titanium dioxide with a solution of calcium nitrate and p hosphorous esters. This composite is deposited on to commercially pure tita nium plates, mechanically polished or blasted with pure crystalline aluminu m oxide, using the spin-coating technique. These coatings are then fired at 650 or 850 degrees C for various times. The samples are characterized by X -ray diffraction for their crystallinity, X-ray photoelectron spectroscopy for their surface chemical composition and scanning electron microscopy for their topography. Samples treated at 850 degrees C present a well-pronounc ed crystallinity, and a high chemical purity at the surface. The topography is strongly related to the viscosity of the precursor and the substrate pr e-treatment. Possibilities to structure the outermost layer are presented. (C) 1999 Kluwer Academic Publishers.