Need help with masking objects

See image.

What I’d like to achieve here is to not render the teeth behind the transparent gums material, or find a way to NOT render any part of the teeth that is contained inside the gums model.

Is this possible?

I’m a 3d veteran, but a Unity novice. Sorry if this is a dumb question.

=> Make your transparent gums material write depth.
=> Enable depth test for your teeth material, so it will be blocked by your gums.

Sounds promising, but I have no idea how to do either of those things. Can you explain in a bit more detail, or maybe point me to a tutorial that will get me started down the right road?