STOCKHOLM, Sweden — Viking raids gave Norsemen a reputation in medieval Europe as bloodthirsty marauders. Recent archaeological finds show they may also have been vain - caring as much for the brilliance of their teeth as the bite of their swords.

A study of skeletal remains from 1,000-year-old burial sites in southern Sweden suggests some Norsemen used iron files to carve grooves into their teeth, probably to insert colourful decorations, anthropologist Caroline Arcini said.

She believes the grooves, which she found in the teeth of 10 per cent of male skeletons but none of the women, were either pure decoration or meant to show affiliation to a social class or trade group.

Tooth filing was widespread among Indian tribes in America at the time, but Arcini's discovery is the first indication it was also used among medieval Europeans.

Although researchers believe the Vikings were the first Europeans to reach America in the 11th century, Arcini said her discoveries don't necessarily mean the two cultures exchanged ideas on dentistry.

"It is probably just a coincidence," she said. "Things pop up in different places in the world without there necessarily having been any contact."

The Vikings entered recorded history in the late eighth century, when they set out in their long ships to raid the coasts of northern Europe. Starting out as minor expeditions by adventurous chieftains, the raids eventually escalated into full-scale invasions in England and northern France led by Norwegian and Danish kings and earls.

Swedish Vikings headed east, crossing the Baltic Sea and sailing up the rivers of Russia and reaching as far as Constantinople.

Arcini's study, first published in the American Journal of Physical Anthropology, found horizontal grooves across the upper front teeth of 24 men in 557 skeletal remains of men and women at four grave sites.

The grooves, often in pairs or triplets, were too carefully made to be the result of chance, she said.

Arcini, who works for the Swedish National Heritage Board, said it was unclear what colours were used to fill the grooves, but it was likely black or red.

"I think it was rather pretty," she said. "What they had in common was that they had to laugh pretty hard" for the teeth to be visible because the grooves were quite high up.

Arcini hopes further studies will reveal where the practice arose and how it spread.