A couple of minutes ago a piece of my tooth just fell out. I don't know why, I don't know how. I noticed that there was something sticking out on one of my teeth so I started picking at it with my tounge, it didn't take much force to remove. I got the boney fragment from my mouth and it was a piece of a tooth.

My questions are:

What could cause this seemingly random occurance?

and

What might a dentist do to fix this?

(i.e. cast a mold of my tooth or something, crown it?)

I didn't chew on anything hard, or chip my tooth before this.

I think I had a filling on this tooth, not sure.

I'm not underminding you but are you sure it's a piece of tooth? Did it come from your lower front teeth? The reason I'm asking is because a lot of ppl who have formed a lot of tarter on the lower front teeth, on the tongue side so you can't really see it but you can usually feel with your tongue. Some ppl think a piece of tooth fell out when actually it's a piece of tarter. I hope that is your case and not a piece of tooth. Here's what you can do to be sure. If you still have that piece of tooth/tarter try to smash it and see if it will smash to some smaller pieces. If so its tarter. Teeth are the hardest substance in the human body and will not smash like that. And if it is a piece of tooth then your dentist prob will put a bonding or some kind of filling to restore it. It depends on what tooth it is. If it's a big chunk that is missing then you may need a crown or vaneer. If you had a bonding on that tooth already then it might be the bonding that chipped. If in doubt you may want to see your dentist.

No, I actually have the piece of tooth in my hand

Edit: oh! sorry...ill see, also...if its tarter...how come i have a gigantic hole in my tooth, its not just a small thing. I would assume tarter would just be like a small piece, this piece was substantial enough that I assume I am close to the root. It hurts when I try to brush it too.

I think your post answered all my questions in any circumstance anyways, thanks.