Complete dentures stay in place by suction and muscle control.
Suction is created by the forces that act on saliva between the base of the denture and your gums. Have you ever tried to get a thin sheet of plastic or something similar off a wet surface and the thing just appears glued in placed? Do you know what I mean? The same basic forces that are at work there, are at work in your mouth. But because the mouth is a complicated moving 3D shape and not just a flat surface, it is a little harder to achieve.
Some dentures have remarkable suction, and with just the simple forces of saliva, take some real effort getting out. These patients have a particularly favourable environment for dentures, namely good anatomy (ridges), good saliva and a correctly made set of dentures. I delve into more detail about successful complete dentures
in another article.
When you have a new denture, the worst thing you can do, is coat it copiously with denture adhesives
to hold it in. The acrylic surface of your denture needs to be properly wetted by your saliva before it starts to get some good suction and this can take a good week. There are many other factors involved in making, achieving and keeping this suction and I will go through them in this series.
The reason having a single tooth to hold in a denture is often a bad idea, is that this tooth allows air underneath the denture base, breaking the seal and suction that the saliva is trying to create. Yes the tooth may have a clasp on that stops the denture from falling out but it is also preventing the denture from sticking in. As with the plastic sheet on the wet surface… once you manage to get air underneath, breaking the seal, it no longer grips and comes off easily.