The greenies thing is a missunderstanding. You have to watch them like any bone or toy. Any signs of gulping it down then take it away if they sit there chewing it then theres no problem.

Umm something else I would recomend hmm there is a chew toy made by nickold or something along those lines and it freshes breath and takes care of teeth there are also tons of greenie imitation that are sometimes better. Have you gone down to your local pet store to look?
I'll try and find what I described.