Just from visiting my dentist from time to time, I reckon that the patients there might have a neg. perception of dental professionals.

That is to say, it must be hard reassuring someone that the pain "won't take long" and that "it's almost done now" when it takes a long time!!
How can we reassure our patients without exaggerating or being dishonest?

I remember when one dentist asked if their client was "feeling all right" during treatment. He had asked out of courtesy, but the client made a face and shook his head (as much as could with a drill in his mouth, anyway).
What should one do then? Stop the treatment immediately and just wait for the pain to go away and then resume?
Or just apologize and continue?
If it is the latter, I wonder why one would ask to begin with if it would be useless to help alleviate the pain? Or should we inquire purely on a politeness-basis?