Friends: a tiny bit of experience here....horn softens in hot water, bone
does not (at least calcified bone doesn’t but maybe some juvenile bone
tissue might be a bit flexible with heating, but basically bone doesn’t
soften much if at all unless you are chemically destroying its integrity).

You heat up some horn In hot water or steam and then you can shape it/bend
it or whatever, and then hold it in place until it “sets” (its the
‘original thermoplastic material’).

  You can fiddle with it maybe a couple of times (reheat it), but  then it
gets bad and can crack or weaken so that it’s not strong anymore (not sure
of the chemical reaction, but it  basically gets cooked? or whatever), so
you should try to hold it in the shape you want the first time around and
hold it there for at least couple days (or a week to be safe if you don’t
have extra to practice with).  You can cut the horn open and flatten a
section to make a flat part, for example, lots of things used to have horn
parts, and it can take a nice polish when dry and cured...
Cheers
Claudio