is it possible for it just to get darker thats it and stay alive

to see if its alive hold an ice cube against the tooth in question. if you can feel the cold on the tooth and you have to pull the ice cube away cos it hurts too much, the tooth is still alive. if you can hold the ice cube there for ages, it's probbly dead. if it's dead, you need a dentist!

if you're unsure, see a dentist anyway, i wouldn't wait around, you're obviously concernd or you wouldn't be posting here.

yea, there is a coworker that has a dark tooth. he says its alive and ok. they dont know why it got stained.

the ice cube is a great idea and works. try it on adjacent teeth to get a feel for the response. you can guage how sensitive the tooth is yourself.

if its dead or even just less sensitive, you should see a dentist ASAP. waiting only lets infection grow and reduces the chances for a successful procedure, which would most likely be a root canal.