T. rex was lippy rather than toothy.

For instance, the crocodile monitor lizard (Varanus salvadorii) has bigger teeth relative to its skull size than T. rex. News THE scary teeth of Tyrannosaurus rex and other killer dinosaurs would have been hidden by lips, contrary to film and TV depictions. "I suspect they are right, and that tyrannosaurs had more soft tissue covering their teeth than crocodiles, but I'm still on the fence as to whether they had as much stuff covering their teeth as monitor lizards", says Steve Brusatte at the University of Edinburgh, UK. [Extracted from the article]