teeth disappear when jaw is moved too low

Hi this is my 2nd head I modeled and rigged but the first one did not have teeth, when i added teeth to this one and move the jaw too low the teeth and gums move past the inside of the mouth. it does not matter what weight I give them. how can i fix this?


Without a blend I can’t know for sure, but it sounds like a problem I’ve dealt with.
Does your mesh have a sub-surf modifier? If so, even if you have the verts in the bottom jaw 100% influenced by the jaw bone, the final mesh will be pulled by the verts next to them that are not influence by the jaw. The easiest way to fix it is to add more geometry in the mouth influenced 100% by the jaw.