As a young lad, Bob was caught reading a girlie magazine by his
mother. He explains that he is interested in girls and wanted to know
more about their private parts. His mother, quite shocked by this,
warns him to stay away from girls private parts, as they have nasty
sharp teeth in them. This seems to do the trick throughout his youth,
but unfortunately he still believes this even into his adulthood.
Anyway, one day (somehow) he gets married and even on his wedding
night, he won't go near his wife. She asks him why....
"Because I know about the teeth you have down there", he replies.
"Heh!", says his wife, "I don't have any teeth down there, where did
you get that idea from?"
"You can't kid me", says Bob, "My mum told me about them."
So, in desperation, his wife takes her clothes off and lies on the bed
with her legs wide open for him to have a good look.
"LOOK!", she says, "NO TEETH!"
"I'm not surprised", replies Bob, "not with gums like that!".