Had mine taken out at 18. Was not having any problems with them, just had it done then as a precaution.
They put me to sleep. It was fairly fast. My appointment was at 8am, I got there 7:45am, filled out paperwork, went back at 8am. They explained a little what they were going to do, and I remember looking at the clock and seeing it was 8:17am when they put me to sleep. Next thing I know they were shaking me and telling me to get up and walk around. I got out of the chair and the clock was at 8:50am. I thought something had gone wrong, but no... they took out all 4 that fast. They gave me pain pills which I never used. I went home, slept some, and was at work at 7pm that night.
No pain really. But if you let them get infected or crack and they have to start cutting them and extracting pieces, it could be worse.