I would tackle it by making the material group-teeth for the toon teeth invisible. Then i would grab the teeth from Hiro and make them a morphing prop, parented to the head. a simple open, close morph is all you need. 

It may be posible in Lightwave to slave the teeth morph to the head morph through motion-mixer but I am not sure. It wont add a lot to animation time if you cant.

That should leave all the head morphs intact.  

AS has been said , remove the teeth and you are likely to mess up the head vertex order.

It MAY be possible to identify and replace the vertices from the teeth but I would not try it myself , unless I was REALLY bored .