Dentist?

A guy and a girl meet at a bar. They're getting along so well that they decide to go to the girl's place. A few drinks later, the guy takes off his shirt and washes his hands. He then takes off his pants and washes his hands. The girl looks at him and says: "You must be a dentist!"

Surprised, the guy says "Yes... how did you figure that out?"

The girl says: "Easy. You keep washing your hands." One thing leads to another... They make love... After they're done, the girl says: "You must be a GREAT dentist!"

The guy is very surprised and flattered, he says: "Well, yes, I am a great dentist, but how did you figure that out?"

The girl says: "Easy. I didn't feel a thing!"