The Bureau of Identification was a Cardassian government agency that collected personal information on all inhabitants of the Cardassian Union.
All Cardassians were required to give the Bureau their first molar, usually by the age of ten. Non-Cardassian persons taken into custody for crimes within Cardassian space were also compelled to have a molar removed. This happened to Miles O'Brien when he was arrested by Cardassian authorities in 2370. It had also happened to a Cardassian spy posing as Raymond Boone sometime prior to that year, a fact which was instrumental in uncovering his true identity. (DS9: "Tribunal")