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.
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.