some tips on carving the mouth

hey i have made a few but i want the mouth to look better. so far they are mostly squarish. i want to know how to make some of those curvy ones with neat teeth and real detail in them. so any tips on that would be fantastic. thanks.

Carve deep! I use 2 chainsaws, fire, anything that cuts. Take your time, go slow, but go deep
Good luck and post pics!