Biological reactivity of different crystalline forms of titanium dioxide in vitro and in vivo.

The biological reactivity of two crystalline forms of titanium dioxide, rutile and anatase, has been compared in in vitro and in vivo assays. Rutile and anatase induced similar effects, and both had a very low biological activity in comparison to alpha-quartz. Rutile samples containing trace amounts of nickel or chromium had an activity similar to that of pure rutile.