They did! Atleast in some population, but not to the same extend as we do. There were teeths that had sign of abrasion that were not due to food or foreign particle, but most likely from tooth pick. There are even dental procedure that were perform to remove cavities. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4504065/

Makeshift tooth brush from twig are used in a variety of place and, while there are not evidence, it would not be surprising if people in the past did use those.

At last, people were less prone to dental cavities, maybe 3% to 15% of teeths had cavities. Their overall dental health was just much better than ours.