Final answer:
The most valuable interdental aid for passing floss under the Pontic of a fixed bridge is the dental floss threader. It is specifically designed to navigate dental floss into tight spaces under bridges and between crowns where other interdental aids may not reach effectively.
Step-by-step explanation:
The interdental aid of the greatest value in passing floss under the Pontic of a fixed bridge is a dental floss threader. This simple yet effective tool is designed to help guide dental floss under prosthetics, such as bridges, and between connected crowns where regular floss cannot easily reach. While interdental brushes, water flossers, and wooden interdental cleaners have their own benefits, the dental floss threader is specifically useful for bridgework because it allows the user to precisely maneuver floss for thorough cleaning underneath the Pontic.