I would wait until your mercury fillings and root canals are all out and all cavitations (if you have them) are done before chelating. For just mercury, some Dentists have you do some chelating beforehand. I prefer people wait until immediately after so they don't get ill.
Dental burs are used for several purposes, including the preparation of teeth cavities and, in many cases, preparation of the teeth themselves for crown and bridgework and partial dentures. They are also used to remove dead jawbone in cavitation surgery .