what if he didn't breathe through his mouth though, or didn't breathe at all? how could he have had breath? besides, he might have the things that some animals have where their teeth rub against each other where their mouth opens and closes so that they can clean their teeth.
The Imprisoned got out of Jail, and tried to make a new friend. Then the person he was trying to meet started cutting off his toes and jamming a spike in his head.
He knew something must be wrong, so inside his little prison he thought about it.
Then he realized- he hadn't brushed his teeth in a millenia. He grew arms, and brushed his teeth, and tryed to make friends again.
But they wouldn't stop slashing at his toes.
The Impisioned is just a poor, misunderstood creature.
... I can't decide if I should be serious here or not. xD
Anyway, if I'm not wrong, having multiple rows of teeth might increase the amount of bacteria they produce. Also, when you sleep, the amount of germs in your mouth multiplies, which is why you always have bad breath when you wake up.
I think it's a safe guess that the imprisioned sleeps a lot, so... yeah, it doesn't add up to a flowerfield when you put all that together, that we can be sure of.