A trip to the Dentist

A guy is having problems with his teeth, so he goes to the Dentist. The Dentist takes a look and say "I see the problem, I need to pull 3 of your teeth" and reaches for a syringe. The guy says "No no I'm scared to death of needles"
The Dentist says "Well, what about laughing gas? " The guy says "I can't, I'm too claustrophobic to have that mask over my face".
The Dentist says "What about pills ?"
The guy says "Oh that's fine, I can take pills".
So the Dentist reaches in a drawer, hands the man a pill and he takes it.
The guy says "What did you give me ? "
The Dentist says "Viagra"
He says "Why in hell would you give me Viagra ?"

The Dentist says "Well, in about half an hour when I start pulling them teeth, you're gonna need something to hold on to"