The Tyrannosaurus rex primarily used its teeth to defend itself. The T-rex was a predator, and the structure of its teeth and skull allowed it to defend itself well.
The Tyrannosaurus rex had very large teeth. These teeth were conical and serrated, which allowed it to bite into flesh and grip it strongly. This dinosaur's strong neck muscles also contributed to its biting ability. Scientists estimate that the Tyrannosaurus rex could eat up to 500 pounds of meat in one bite. The dinosaur probably crushed and broke the bones of its prey as it ate. The Tyrannosaurus rex had a jawbone that was, on average, at least 4 feet long, which was extremely large for a dinosaur.
Each adult Tyrannosaurus rex had 50 to 60 teeth in its mouth. Some teeth were small, while others were more than 9 inches long. If a tooth broke, a new tooth would grow in to replace it. For this reason, an adult Tyrannosaurus rex could have had many different sizes of teeth at any given time.
The Tyrannosaurus rex probably did not use its arms as a primary defense. While it could grab prey with its forearms, these arms were too short to reach its mouth. The dinosaur also had eyes that aided it in predation. It had proper depth perception and eyes that faced forward in its skull, which gave it the advantage of enhanced visual acuity to spot prey.