LITTLETON, Colo. — A dentist found the source of the toothache Patrick Lawler was complaining about on the roof of his mouth: a 10-centimetre nail the construction worker had unknowingly embedded in his skull six days earlier.

A nail gun backfired on Lawler, 23, on Jan. 6 while working in Breckenridge, a ski resort town in the central Colorado mountains. The tool sent a nail into a piece of wood nearby, but Lawler didn't realize a second nail had shot through his mouth, said his sister, Lisa Metcalse.

Following the accident, Lawler had what he thought was a minor toothache and blurry vision. On Wednesday, after painkillers and ice didn't ease the pain, he went to a dental office where his wife, Katerina, works.

"We all are friends, so I thought the (dentists) were joking ... then the doctor came out and said `There's really a nail,' '' Katerina Lawler said. "Patrick just broke down. I mean, he had been eating ice cream to help the swelling.''

He was taken to a suburban Denver hospital, where he underwent a four-hour surgery. The nail had plunged about four centimetres into his brain, barely missing his right eye, Metcalse said.

"This is the second one we've seen in this hospital where the person was injured by the nail gun and didn't actually realize the nail had been imbedded in their skull,'' neurosurgeon Sean Markey told KUSA-TV in Denver. "But it's a pretty rare injury.''

Lawler was recovering Sunday in the hospital, where he was expected to spend several more days.

Despite his lack of medical insurance and hospital bills between $80,000 and $100,000 US, Katerina Lawler said her husband is in good spirits.

"The doctors said, `If you're going to have a nail in the brain, that's the way you want it to be,' '' she said. "He's the luckiest guy, ever.''