The difference is that sharks continually replace their teeth.
“New teeth are continually grown in a groove in the shark’s mouth and the skin acts as a “conveyor belt” to move the teeth forward into new positions. Sharks’ specialized teeth have allowed sharks to develop a very strong jaw. Without the ability to quickly replace teeth, a shark’s jaw could not have developed as powerful of a bite. The number of teeth they routinely lose while catching prey would outweigh the quick-kill benefits of their crushing jaw strength.”
The difference is that sharks continually replace their teeth.
“New teeth are continually grown in a groove in the shark’s mouth and the skin acts as a “conveyor belt” to move the teeth forward into new positions. Sharks’ specialized teeth have allowed sharks to develop a very strong jaw. Without the ability to quickly replace teeth, a shark’s jaw could not have developed as powerful of a bite. The number of teeth they routinely lose while catching prey would outweigh the quick-kill benefits of their crushing jaw strength.”
http://www.sharksavers.org/en/education/biology/shark-teeth1/