Adding vampire fangs to base race's/custom race's

[Kaz Aanh]

I'm having a little with adding fangs to the base Breton race ( with ECE ) and I can't figure it out. I'm planning later to make a custom race based on it.

 

I know there is a MouthHumanF.nif  and MouthHumanF.tri but how do they work? 

Or maybe there is a better way to add fangs ?

 

Geezus CK is so unintuitive.

 

Help is really appreciated.