How are craze lines on teeth fixed?
Doctor Answers 1
Crazed lines are common
The most common treatment is NO treatment. These lines are signs of normal wear and tear, and thermal changes. Imagine hot coffee followed by ice cream. The rapid temperature change can cause internal cracks. They may do nothing at all, so treatment is usually not indicated. I highly doubt the drill did it, especially since composite removal/polish is common.
It is likely that the lines were there already, you just weren't looking with much scrutiny before.