Hi Judo3052,
if you read this in a research paper, would you mind posting it here? Not every research is a good one and there is a lot of BS around. As you mentioned, companies trying to scare people and sell products.
From my own interest in longevity and health, the things that play a role in how long you live are nutrition, fitness, good sleep, the amount of toxins in your environment, and the quality of your relationships. And even those are rather suggestions than "confirmed" because you can't really do this kind of research on humans.
Anyway, hard as I try, I can't figure out how dentures could affect any of it. On the contrary I know many happy people who now, with dentures, have a much better life than before.