John went to the Dentist with a bad toothache and the Dentist told him he need an extraction.

Dentist said" I'll give you novocaine"

"No, said John, it never works on me"

"I'll give you some gas"

"No, said John, I get very sick from that"

"Well, said the dentist, the only thing left is viagra"

"What will that do"

" It will give you something to hold on to, when I pull the tooth"