Which chemical reduces exposed silver halide crystals during the developing process?

During the developing process in dental radiography, hydroquinone plays a crucial role as a reducing agent. When the film is exposed to radiation, silver halide crystals are formed, which are sensitive to light. The purpose of the developing solution is to convert these exposed silver halide crystals into metallic silver, resulting in a visible image on the film.

Hydroquinone specifically reduces the exposed silver halide crystals by donating electrons, which leads to the reduction of the silver ions present in the crystals to form solid metallic silver. This is critical in developing a clear and detailed radiographic image. The choice of hydroquinone as the reducing agent is due to its ability to provide a high contrast image while enhancing the overall quality of the film.

The other chemicals mentioned have different roles in the developing process. For instance, acetic acid is used in films as a component of the stop bath to halt the developing process, sodium carbonate acts as an alkaline agent to assist in the development, and potassium bromide serves as a restrainer to prevent fogging of the radiograph. However, it is hydroquinone that specifically reduces the exposed silver halide crystals during development.