Two words that don't go together...?

This is sort of a riddle.  Think of one of those things you have to do, that isn't necessarily any fun, you spend money, but your smile is always better for it?  Think of two words you wouldn't use in the same sentence, most of the time.  Any guesses?

Yeah, dentist and fun.  Well, Dylan proved that theory wrong today.  She went to the dentist and actually had fun, learned some new things, got her teeth polished and saw the dentist plus came home with a treasure trove of princess tooth brushes, stickers and goodies.  Now that is seeing the dentist in style.  She cracked us up:  as the hyegenist finished up with a little learning and a little poking around in D's mouth, Dylan said:  "I wanna see the boy dentist."  Meaning she wanted to see the doctor today.  Luckily, he just came in for the morning (we were there early at 8am) and Dr. Naden came in and gave Dylan a clean bill of teeth health, told her about when she'd get her adult teeth and to keep brushing.  Not a bad second visit to one of those places most of us don't like.