A while back someone else on here suggested a way to train them to take things gently and for me and Rory, it really worked.
Take a treat and make a fist around it, just allowing a tiny area of it to poke out of the top of your hand.
Show your pup and allow him to try and take it. While they might try and bite it out straight away, they will shortly try and lick it out. Couple this with saying 'gentle, gentle' and after they have been licking for a while, open your hand and let them sort of lick it right up.
Eventually they will get that gentle= no teeth!