Researchers studied hominid jaws from the Dmanisi Republic of Georgia - the earliest evidence of primitive humans outside Africa.
They found evidence of gum disease caused by repeated use of what must have been a basic toothpick.
The findings shed light on why the Georgian hominid mandibles, or jaws varied widely in shape from each other.
Ani Margvelashvili, lead author of the study at the University of Zurich, Switzerland, said that scientists dealing with fossil hominid mandibles should pay close attention to tooth wear and the fossil individual's age.
"Progressive tooth wear triggers bone remodelling processes that substantially modify the shape of the jaw during an individual's lifetime. These effects are typically underestimated when attributing fossil hominid jaws to different species," she told 'BBC News'.
"The individual who was using a toothpick was young, as his or her teeth were not worn down. We also discovered a damaged area between the tooth area and the gum. There was a small cylinder-shaped lesion - in this area, if you place a toothpick it goes through," she said.
One of the jaws examined had lost all the teeth except for one canine. The mandibles that showed the least wear were from younger individuals, researchers found.
The study analysed four mandibles from one of the biggest collections of well-preserved early human remnants known anywhere in the world. The Dmanisi site has been valued as an important place to look at how hominids migrated from Africa.
It is not yet known what species the Dmanisi hominids were. They were once believed to be Homo erectus who first ventured out of Africa.
The Dmanisi individuals were short, long-armed and small-brained. The fossils are therefore now sometimes referred to as Homo georgicus.