As much as I know, TiO2 is an inert material it does not degrade however there are some reports on formation of  apatite crystals on its surface but this is not related to  its degradation. 

Hi Iman Roohani. Thanks for your response. Yes, so far, many informations I gathered are related to the formation of the apatite bone-like layer on TiO2 surface. I also came across a few manuscripts that saying that this material will decomposed but at a very slow rate. The rate of degradation is what I needed. Anyone?

To my humble opinion degradation rate is a subjective term. It is not only dependent on the chemistry of a material but also its dimension. For example a thin layer of polycaprolactone takes 21 days to dissolve in a aqueous solution but a 1 cm cube of PCL will take more than a year to degrades. It maybe worth making a specimen with similar dimension of the one you expect to use in your study and design a degradation study.

Great! I never thought of the size effect on degradation rate.

Our sintered titania scaffold (uncoated) is 6 x 6 mm in size. I know polymer base coatings (PDLLA, PLGA) will degrade within the intended range of tissue engineering usage, but how the titania scaffold itself will decomposed over time?

Finally I found a dissertation discussing the degradation of sintered titania in SBF. This is a report simply filling the gap of degradation study of sintered titania scaffolds both pure and phase-porous structure. Immersion period was set to 6 weeks.

http://etd.fcla.edu/CF/CFE0002555/Menon_Arun_K_200905_MS.pdf

Cheers,

   Ayub