Periodontal disease is a toughy. It's a problem where bacteria attack the bone surrounding the teeth and dissolves it. The bacteria travels along the periodontal ligament. Because of this, teeth can, as I'm sure you have found, fall like dominoes.
Have you considered implant supported dentures? I don't think a toothpaste is going to help as the bacteria is well below the gumline where toothpaste could reach.
If you still have sufficient bone, perhaps LANAP surgery would help. It's laser gum flap surgery to remove areas that can hold the bacteria.
Other than surgical remedies, there's not much you can do if you reached the stage where you are considering pan extractions.
Good luck, but IMO, do put your $ where it can really help.
Best to you,