Conventional dentures are fabricated to stay in place because of their intimate fit with your gums.
Dentures are the fastest, easiest, and cheapest way to replace a full arch of missing teeth. They stay in place with a suction cup effect, your anatomy, gravity, and, for many, denture adhesive.
For those looking to add more staying pair to their existing dentures, a new pair can help and adding dental implants almost always helps for those who are good candidates.