Have you seen an ENT about this problem? I would recommend seeing an ENT since its more under their realm of expertise or posting in the ENT section.
A cavity, if large, can be a source of infection that can't be cleaned out well by brushing, flossing or mouthwash alone. That may be a source of your halitosis. Also, do you brush your tongue as that's another spot that's prone to harboring bacteria.
I ALWAYS HAVE A VERY BAD TASTE AND SMELL COMING FROM MY THROAT. I AM A DENTURE WEARER AND I HAD MY TONSILS REMOVED WHEN I WAS 18. I BRUSH AND GARGLE REGULARLY AND NEVER GO WITHOUT GUM OR SUGARLESS CANDIES IN MY MOUTH. IT DOES VERY LITTLE TO ALLEVIATE THE PROBLEM. I READ THAT STOMACH BACTERIAS CAN CAUSE THIS PROBLEM. I FREQUENTLY GET SORE THROATS, WHEN THE TASTE AND SMELL GETS WORSE.
ANY SUGGESTIONS ON THE CAUSE OF THIS PROBLEM???