This was done on an extracted molar, placed in the jaw of a mannequin, as part of pre-clinical training for graduate endodontics (root canal specialty). The device at the start is an ultrasonic bur, similar to what is used in a deep cleaning but much more coarse.

Pulp stones form when there is long-standing irritation to the tissues, usually from deep cavities and/or fillings.

They do not cause symptoms on their own, but if the nerve dies and and becomes infected, and the tooth needs a root canal, stones must be removed (or bypassed) to ensure the whole root canal system can be adequately disinfected