Anyone who has ever squirmed through a dental cleaning can tell you how sensitive teeth can be. This sensitivity gives important feedback about temperature, pressure—and yes, pain—as we bite and chew our food. However, the sensitive parts inside the hard enamel first evolved for something quite different.
For example. Bear in mind that each animal needs to figure that out on its own as it grows up. Have you heard about humans who are unable to feel pain? Very rare congenital condition. Doctors remove their baby teeth or else they will chew up their tongue and mouth. That’s the sort of thing you need to think about.
A number of animals, birds especially, swallow rocks to help them grind up food in their intestine.
I just am not sure what biological purpose it serves, other then to dissuade eating extremely abrasive stuff all the time. It’s not like if their teeth hurts they can go to a dentist and or nutritionist to get them repaired or tell them exactly what is wrong with their diet.