Final answer:
Hydrogen peroxide is used to bleach a discolored, endodontically treated tooth. It is a common bleaching agent in dental products and can safely break down into water and oxygen gas.
Step-by-step explanation:
The chemical used to bleach a discolored, endodontically treated tooth is Hydrogen peroxide (C). Hydrogen peroxide is a well-known bleaching agent that is used in various dental whitening products, including whitening toothpastes. It has the ability to break down into water and oxygen gas, which provides the bleaching effect on teeth. Hydrogen peroxide is a common household disinfectant as well, and when used in dilute concentrations, it can be safe for use in oral applications. Other substances mentioned, like sodium hypochlorite, are more commonly used as disinfectants and bleaching agents for non-dental purposes.