It’s hard to predict how much of the upper and lower jaw will remain after 20 years without teeth. When teeth are removed, often the bone that held them in slowly shrinks over time. This doesn’t happen to everyone, but it’s normal after tooth removal. It’s important that dentures are made properly to fit well and keep minimum stress on the bone. It’s not likely that you’ll have all the bone you started with after 20 years of not wearing a denture. Your denturist should annually examine your mouth to assure ideal oral health, including the bone level that would be below your dentures.