Just a note on a pet peeve: Diamond is (still, possibly) the hardest known natural substance*, but it is brittle. As such, it probably wouldn’t be great for teeth, unless the creature were constantly replacing them like a shark.
* pure Lonsdaleite (“hexagonal diamond”) and certain compressed versions of buckminsterfullerine are harder, but are not known to occur in nature in significant amounts
* pure Lonsdaleite (“hexagonal diamond”) and certain compressed versions of buckminsterfullerine are harder, but are not known to occur in nature in significant amounts
