How Retention Works
Of all the things that may concern denture wearers, retention probably tops the list. Retention broadly refers to the ability of your denture to remain stable and snug to your ridges while speaking and eating. Understanding how denture retention works and the way dentures are designed will give you better insight when discussing these issues with your practitioner.
Capillary retention and suction principally hold in upper dentures. For most patients this provides ample retention. If however you are finding less than adequate suction there are a number of potential problems you need to be aware of.
Size of Ridge
If your ridge is very small compared to the size of your denture. The smaller surface area being covered may not be adequate to counter the leverage force of a large denture when chewing.
Dry Mouth
In order for capillary retention to work a reasonable volume of saliva must be present. Many of today's medications have unfortunate side affects that can reduce salivation leaving patients with dry mouths and subsequently loose dentures. Fortunately there are products available that can maintain oral lubrication and if you suffer this condition you should discuss this option with your dental provider.
Shape of palate
No two mouths are exactly alike in this regard. As a general rule palates that are broad and shallow will provide greater retention than those that are narrow and vaulted. If you have ever tried to pick up a sheet of glass off a moist counter top this aspect of capillary retention will be more clear. Pulling the glass straight up is very difficult. However sliding it sideways provides much less resistance. Now imagine your denture as the plate of glass and your counter top your palate.
Post Dam
This is the technical term used to describe the small raised bead on the posterior edge of your denture. The positioning of this bead is crucial to maintaining a seal. If you remove your upper denture, lift your tongue to the roof of your mouth and curl it back. You will note your palate is quite firm to a certain point and then suddenly becomes soft and supple. It is at this junction of firm and soft tissue the post dam needs to be placed. If it is placed too far forward of this point the bead will not press well into the firm tissue and your seal can be compromised. If it is too far back into the soft tissue you will have a tendency to gag, and a gag reflex will most certainly dislodge your upper denture.
Malocclusion
Incorrect positioning of upper to lower teeth can cause dentures to rock particularly when chewing causing suction to be compromised.
Resorption of ridges
Given the fact your ridges will slowly shrink over time and your dentures do not shrink with them. Greater discrepancies will develop between the shape of your denture and the shape of your ridge. This will result in a slow weakening of capillary seals and greater ability for dentures to rock and become unseated.
These are a few of the factors that affect how your upper denture performs. In my next article we will be exploring the very different workings of a lower denture.