I removed some speculation regarding Vulcans and tricuspids:
The scan of T'Pol's dentition shows what appears to be a tricuspid in the area of a Human upper bicuspid and molars in the area of the Human lower bicuspid. The most likely probability is that Vulcan dentition originally had no bicuspids and has degenerated some molars (4-cusped) to tricuspids. Leaving their violent history behind (a culture which would evolve dentition with many strong teeth), evolution most likely "degenerated" some of the larger teeth to tricuspids. Their peaceful cultured existence and vegetarian diet of prepared foods (i.e. soft foods) and insistence of the use of flatware for cutting food and placing food in the mouth (instead of biting) has little use of strong teeth in great numbers.
--Jörg 14:32, 17 May 2007 (UTC)