Dentist
A guy and a girl meet at a bar. They get along so well that they decide to go to the girl's place.
A few drinks later, the guy takes off his shirt and then washes his hands.
He then takes of his trousers and washes his hands again.
The girl has been watching him and says, "You must be a dentist."
The guy, surprised, says "Yes! How did you figure that out?"
"Easy," she replied, "you keep washing your hands."
One thing led to another and they make love.
After they have done, the girl says, "You must be a good dentist."
The guy, now with a boosted ego says, "Sure, I'm a good dentist, How did you figure that out?"
"Didn't feel a thing!"