I tried teflon tape first for an italian BB that I must have slightly cross threaded - the new sealed unit would work it's way out after 20 miles or so. I ended up going with blue loctite and that's held for about 1000 miles so far (retired for winter.)
When I unthreaded the BB instead of just re-tightening, I saw that the teflon tape had pretty much disintegrated, getting pushed back by the threads... There were a few clumps, but not an even coverage like you'd expect.
Not sure if that helps or not...