Patrick Lawler went to the dentist because of a persistent toothache on the roof of his mouth. The dentist soon found out the cause: a four-inch nail the construction worker had unknowingly shot into his skull almost a week earlier!
This, and more bizarre X-rays can be found at 2Spare: Link - via Eduyayo
What, don't believe the story above? Here's the full story: Link
*fires off a nail gun into his mouth* "AAAH the roof of my mouth is bleeding! Oh well it probably is just my imagination!"