Dentist

Dentist: "Would you help me out? I'd like you to give a few of your loudest screams."
Patient: "Why, Doc? It isn't all that bad this time."
Dentist: "Well, there are about 20 people in the waiting room right now, and I don't want to miss the five o'clock Braves game on Channel 4."

Physics Rx

One day our professor was discussing a particularly complicated concept. A pre-med student rudely interrupted to ask, "Why do we have to learn this stuff?"
"To save lives," the professor responded quickly and continued the lecture.
A few minutes later, the same student spoke up again. "So how does physics save lives?" he persisted.
"It keeps the ignoramuses out of medical school," replied the professor.

The Careful Dentist

There's this woman who goes to the dentist.  As he leans over to begin working on her, she grabs his balls.  
The dentist says, "Madam, I believe you've got a hold of my privates."
The woman replies, "Yes...  And we're going to be careful not to hurt each other, aren't we!"