"Pain Killer" for Root Canal?

A man went to the dentist because his tooth was hurting. The dentist told him after the examination that he needed a root canal. The man replied, "O.K. lets do it."

The dentist told him he will feel a pinch when he gives him the shot of the numbing agent.

The man says, "No, Doc, I am allergic to that."

The doctor tells him, "O.K., then, we'll give you nitrous oxide."

The man says, "I am allergic to the gas."

So, then the doctor gives him two pills with a glass of water and the man takes it. The doctor comes back in 10 minutes and the man says, "Doc, will those two blue pills kill the pain?"

The doctor replies, "No, that was Viagra."

The man says, "Viagra? I don't need that! What's that going to do for me?"

The doctor replies, "Well, it'll give you something to hang onto."