Full upper dentures cover the roof of the mouth (palate). A very thin layer of saliva between the roof of the mouth and the denture creates suction, which keeps it firmly in position. Your facial muscles and tongue also help to keep it in place.

There are tiny taste buds on your palate so if you wear an upper denture, it can affect how you sense the temperature and taste of food.

Full lower dentures are held in place by the tongue and cheek muscles. As you get older, your cheek muscles may become weaker, so your lower dentures can be slightly more difficult to keep in place than your upper dentures.

However, dentures should fit the mouth exactly so denture adhesive cream (fixative) shouldn't be necessary.
If you have full dentures, you will need to remove them for cleaning and take them out at night.