Mystery drilling: ancient teeth endured dental procedures.

Welcome to a time so long ago that people with no dental insurance still could get their teeth drilled, and perhaps filled. Flint-wielding specialists performed the work between 9,000 and 7,500 years ago. A total of 11 teeth from nine adults who lived during that period contain holes drilled with sharpened flint points, according to a new report.

The teeth came from residents of a prehistoric farming village called Mehrgarh in what is now Pakistan.

These discoveries represent the earliest known examples of dental work, say Roberto Macchiarelli of the University of Poitiers in France and his colleagues. Drilling occurred in cheek teeth, indicating that the dental alterations weren't intended for display or decoration, the scientists contend.

Four teeth exhibit decay near drilled holes, Macchiarelli's team says in the April 6 Nature. Three drilled teeth came from the same individual, and another tooth was drilled twice. Intriguingly, no instance of drilling has been found in teeth from a 6,500-year-old cemetery at the same site.

"We have no idea why the practice [of tooth drilling] disappeared at that time," says anthropologist and study coauthor David W. Frayer of the University of Kansas in Lawrence. "In fact, we're not sure why it was done in the first place, since less than half of the drilled teeth had [decay]."

Drilled holes in the Mehrgarh teeth were 1.3 to 3.2 millimeters in diameter with a depth of 0.5 to 3.5 mm. Edge smoothing indicates that drilling was performed on living individuals whose continued chewing caused further dental wear.

Some type of filling may have been placed in drilled holes, which would have exposed sensitive tooth areas, the researchers suggest. The researchers haven't yet identified filling traces on any of the teeth.

Analyses with a scanning electron microscope and a computerized-tomography scanner identified concentric ridges on the inside wails of the holes in the teeth. Macchiarelli's group regards these marks as products of prehistoric drilling tools.

Ancient inhabitants of Mehrgarh attached sharpened flint to wooden rods and used the instruments to fashion beads out of shell, turquoise, and other materials. "Presumably, know-how developed by skilled artisans for bead production was transferred to drilling teeth in a form of [early] dentistry," Macchiarelli says.

Wielding a flint-tipped model of the prehistoric tools, members of Macchiarelli's team drilled holes in cheek teeth on a modern human jawbone at a rate of about one per minute.

Since some of the drilled teeth also had cavities, "it's not a stretch to suggest it might have been early dentistry," remarks anthropologist David DeGusta of Stanford University. DeGusta and his colleagues have examined a 1,000-year-old Native American jawbone that contains a tooth with a hole drilled at the site of gum disease.

Anthropologist John R. Lukacs of the University of Oregon in Eugene calls the relatively small holes in the Mehrgarh teeth "unusual and somewhat enigmatic." He awaits further analysis to confirm the existence of ancient dentistry.