I don't recall there being any indication they do. I reviewed it a couple of weeks ago here.
It is an awesome movie. They mainly attack them with UV light type weapons so they wouldnt have regenerated from it anyway.
Oh that looks very very cool. :D
Wow, that looks like they had a lot of fun making.
They don't regenerate because they are based on actual folklore.A D&D Troll has as much in common with the Vitterfolk and Huldrefolk as a Mars bar has with the red planet. They share a name.
I say again: NUUUUUUUUUUUUUUU! D:
According to Wikipedia (but it's uncited), trolls' ability to regenerate comes from 'Three Hearts and Three Lions'.