Which is the best product on the market to buy to keep your dentures from coming loose ?

Matter of preference: Check with your dentist to see if there is something that can be done to your dentures to increase the retention. It may be that they are too old and the gums have receeded and need to be rebased or remade if so this may allow you to not need the adhesive.

Denture adhesives: The two most common are poligrip and fixodent. Patients have their own preferences and there is no one "best" product. Have your own dentist evaluate whether your dentures should be relined or remade. You should see a dentist every year, even without teeth to evaluate denture and do cancer screening. Also consider implant retained denture for more stability and retention.