The thing's not a tooth. A cast of it was identified by a few dentists as a tooth, but none of the paleontologists he showed it to were convinced. It's a simulacrum, a natural object that looks like something we recognize. I wonder if there are any reliable studies of the thing published.
There's a good blog post on it with a really bad picture and some excerpts from the 1926 Literary Digest describes it calling it a tooth.
Somehow the tooth's enamel was replaced by carbonized and the roots by iron. The guy who found the thing was, of course, a creationist who instantly identified it as evidence of the flood.
Just for grins let's say it is evidence for the flood...so now that means the creationists have one piece of evidence to set against something like the 400,000,000 plus fossils in museums and universities around the world.
Oh, the "tooth" is about 1/3 of an inch long...at best a baby tooth. Way to go God.
Bad Archeology: The ‘Beartooth Highway tooth’