How do regular dentures stay in?
The inside of an upper denture covers the roof of the mouth. When the denture is pressed up into the roof of the mouth it pushes some of the gum tissue out of the way creating a vacuum suction effect. This suction keeps the denture in place. The amount of suction depends on how much of the “ridge” is left.
The “ridge” is the area of gums and bone that remains after all of the teeth are removed. Here are examples of a lot of ridge and very little ridge.In the first image the “roof of the mouth part” of the denture will be very tall and convex and can easily be pressed into the roof of the mouth to create suction. In the second image the ridge is almost flat. That means that the inside of the denture is also flat and therefore the denture can not be pushed up into the roof of the mouth as much and will not have any suction.
A lower denture stays on in a different way. Since there is no roof of the mouth on bottom, the lower denture relies on long extensions beyond the ridge to hold it in. These long extensions, flanges in dental speak, extend underneath the tongue so the tongue holds them down. They also extend as far back as possible to increase the amount of “grip” they have. This is also dependent on how much ridge is left. The more ridge the taller the flanges can be and the better the denture will stay put.
What happens to the ridge?
Over time the ridge starts to disappear. Your body was designed for teeth, not dentures, and the pressure of dentures causes the ridge to disappear at a very fast rate. Even without wearing dentures the ridge disappears over time, but dentures greatly accelerate the process. If you wear dentures or talk to a denture wearer, they’ll probably tell you that when the dentures were made they fit perfectly and 5 years later they’re very loose and require denture adhesive to stay in. The dentures haven’t changed, the ridge has shrunk.
How do implant dentures stay in?
There are a few ways that implant dentures can stay in. They can be permanently screwed in (“fixed”) or they can be removable. Whether or not someone can have a “fixed” denture depends on a number of factors, but the most important is how many implants are placed. Since it’s never removed it needs more implants to support it. More implants obviously increases the cost.
Whether with “snaps” or something else, the other option is a removable denture that no longer relies on suction to keep it in. Because of this the upper denture no longer needs to cover the roof of the mouth and the whole denture can feel smaller and more natural. The implants are placed under your gums and they stick out with a button attachment on them. The inside of the denture has the other side of the button and they snap together to stay in.
In the image below the black circles in the denture are one half of the button. The side view shows the other side of the button (the gold cap) sticking through the gums from a side view.
For a fixed option, the buttons are changed to screws and the part that sticks through the gums is a screw hole.
Implants provide a big advantage in and of themselves because they mimic a tooth root. Your body thinks it’s a tooth and the ridge does not disappear in the area around the implant.