Traditionally grinding things with stone ended up with people eating stone which ground their teeth down[1]:
> "A. When soft stone like sandstone was used for milling grain, as the ancient Egyptians often did, residue from millstones could cause a serious problem over a lifetime, said Dr. Robert K. Ritner, associate professor of Egyptology at the Oriental Institute of the University of Chicago. Egyptian teeth have been well studied in mummies, and only the rare mummy had good teeth, said Dr. Ritner, who lectures on Egyptian medicine. ''They usually had heavy abrasion, and were sometimes so worn down at the crown that the pulp or even the root was exposed, which must have been horribly painful,'' he said. The Egyptians were obsessive about cleanliness, using a natural soda compound called natron for cleaning the mouth and sometimes a chewing reed to massage the teeth. They had few cavities, and the damage seen in studies pioneered by the English researcher F. Filce Leek almost certainly resulted from the residue of disintegrating millstones."
> "A. When soft stone like sandstone was used for milling grain, as the ancient Egyptians often did, residue from millstones could cause a serious problem over a lifetime, said Dr. Robert K. Ritner, associate professor of Egyptology at the Oriental Institute of the University of Chicago. Egyptian teeth have been well studied in mummies, and only the rare mummy had good teeth, said Dr. Ritner, who lectures on Egyptian medicine. ''They usually had heavy abrasion, and were sometimes so worn down at the crown that the pulp or even the root was exposed, which must have been horribly painful,'' he said. The Egyptians were obsessive about cleanliness, using a natural soda compound called natron for cleaning the mouth and sometimes a chewing reed to massage the teeth. They had few cavities, and the damage seen in studies pioneered by the English researcher F. Filce Leek almost certainly resulted from the residue of disintegrating millstones."
[1] https://www.nytimes.com/2002/08/06/science/q-a-teeth-and-mil...
[2] https://boards.straightdope.com/t/do-whole-grains-damage-you...