Effect of aging time of sol on structure and in vitro calcium phosphate formation of sol-gel-derived titania films.

Titanium and its alloys have been used successfully in the manufacture of orthopedic and dental implants to replace damaged bone tissue. In this study, different sol-gel-derived TiO(2) coatings were produced on titanium substrates using different aging times (5, 10, 24, or 48 h) of the sol before dipping the coatings and varying numbers (one, three, or five) of coating layers. The influence of the aging time of the sol on the structure of the titania coatings with respect to in vitro bioactivity was investigated. The in vitro bioactivity tests were done in a simulated body fluid (SBF). The sol properties were monitored using a capillary viscometer and dynamic light scattering to determine the viscosity and particle size, respectively. The topography of the films was characterized using atomic force microscopy. The various sol aging times and numbers of layers produced differences in the topography of the titania films. For the coatings with one and three layers, the aging of the sols had an influence on the height of the peaks (lower with longer aging times) although the peak distance was about the same. The number of coating layers had a stronger influence. The distribution of the peak distances became narrower with an increasing number of coating layers. The coating with three layers (top coating prepared after 24 h of sol aging) and the coatings with five layers had a similar distribution of peak distances (15-50 nm), which was favorable for calcium phosphate formation. On these substrates, calcium phosphate formation started within 3-6 days of immersion in SBF. The aging time of the titania sol and the number of coating layers were found to have a strong influence on the surface topography in the nanometer scale of the titania films. The results indicate that the topography of the outermost surface is of importance for in vitro bioactivity.

Influence of sol and surface properties on in vitro bioactivity of sol-gel-derived TiO2 and TiO2-SiO2 films deposited by dip-coating method.

Different sol-gel-derived titania and titania-silica films were prepared and their properties related to in vitro bioactivity. The films were prepared by depositing the sols on the substrate surface using a dip-coating method. The sols were monitored carefully as a function of time, using rheological techniques and dynamic light scattering. The topography of the films was characterized using atomic force microscopy, and thicknesses and refractive indexes of the films were evaluated by fitting transmittance spectra measured in a wave length region of 370-1100 nm with a spectrophotometer. The in vitro bioactivity tests were performed in simulated body fluid. Surface topography was found to be of great importance with respect to the bioactivity of the studied films.

Calcium phosphate induction by sol-gel-derived titania coatings on titanium substrates in vitro.

Titanium and its alloys are used widely in the manufacture of orthopedic and dental implants. Sol-gel-prepared titania is able to stimulate bone-like apatite formation in in vitro and in vivo cultures. These materials can be used, for example, as coatings on dental and orthopedic implants. However, the processes that lead to apatite formation are not fully understood. In this study different kinds of titania coatings on commercially pure titanium (c.p. Ti) were tested for apatite-forming ability. The rate of apatite formation is considered to be descriptive of a material's bioactive (bone-bonding) potential. Apatite-forming tests were done in simulated body fluid (SBF). Apatite-forming ability was highest with the addition of valeric acid to sol (600 degrees C) or with sintering sol-gel coatings at 450 degrees-550 degrees C. At that temperature range calcium phosphate forms on the coatings in 1 week. Calcium phosphate forming is observed in 1 day on standard coatings sintered at 500 degrees C.