I Have Had a Bridge for 40 Years - What is Best to Do in Replacing Bridge Please?

Your options depend on how long of a span your current bridge is and whether replacing it with an even longer bridge is wise.  If there is decay under one of the anchor teeth, you are better off opting for a removable partial or individual implants which allow you to keep everything clean easier than with a bridge.

Your dentist is following the right path, the first thing to assess is if the teeth that are holding the bridge are still restorable, and from what I understand the only way to find out is by removing the bridge and getting all the decay out.

If the teeth can be restored you can get a new fixed bridge, if they are not implants would be the first option to give you again  a fixed restoration.

 

Your dentist is right.  If the bad tooth has to go, you will need 2 implants (assuming the bridge replaces a missing tooth).  A less expensive alternative is a removable partial appliance.  If the tooth can be saved, then a new bridge can be made.