It had to do with Eddie needing parts of the people to be able to enter our world. He could visit our world for brief periods of time this way. Why he took the teeth specifically instead of something else, I'm not sure.

Thanks for the explanation

No problem! That tooth monster was one of the creepiest things I've seen in a horror movie/TV in a while. I wonder if the writers thought the monster would be creepy cool to create but didn't really think of a great reason why the teeth were taken.

I get the same feeling. That was a great monster. I wish they'd written in a better idea for why he became a tooth monster. It was a great little series. Well written, acted, filmed and produced. I feel like i'm being a bit picky. But the reason for him to focus on the teeth seemed like an after thought and glossed over. I completely missed the bit about him needing the body parts. I was probably tired and missed it. But i'm still looking forward to the next series. Hopefully they can keep up the good storytelling. It had a real creepy vibe to it.

I don't think they really spent much time explaining it. It might have just been a slight mention in the final episode. Over all, great season! I'm also looking forward to the next one. This is the kind of show that I've been wanting American Horror Story to be.