STABILITY ON YOUR LOWER
The way that a lower denture is retained in the mouth is very different than the way an upper denture fits. The ability to wear a lower denture tends to be more of an acquired skill, rather than a given. Lower dentures have little or no suction, and rely on the musculature in your cheeks, tongue, and the floor of your mouth learning to work with the denture, helping to stabilize and limit movement. This skill takes time to develop and is often where patients express frustration with dentures that tend to be somewhat mobile when speaking and chewing. As time passes this mobility diminishes and most patients have adapted in two to four weeks.
The size of a lower ridge can also make quite a difference. Patients who have worn dentures for many years have often suffered great resorbtion leaving a diminished and flat ridge for the denture to fit to. This in turn allows more movement of the denture when chewing and can lead to more sore spots or bruising of the tissue. It is not uncommon to have patients complain that their ability to function well with lowers declines as they get older. Another significant difference between upper and lower dentures is the amount of ridge covered to distribute your bite force, which for some can be in excess of 400lbs per square inch. An upper will cover the entire palate while a lower must have a large portion cut away to accommodate your tongue. A rather simple analogy my father used to make is the blunt end of a pencil vs. the sharp end. Push it onto your tissue, the side with minimal pressure distribution hurts the side with maximum does not.
The components required in denture design to create good stability, and comfort would be as follows:
- Good impressions that yield an accurate fit spreading the bite load out over the entire ridge.
- Proper denture broader lengths that allow for free movement of musculature and tissue attachments or frenum cords.
- Molars that are placed proximate to the center of the ridge so as not to create a teeter totter action when chewing.
- Proper occlusion between upper and lower denture, meaning that in your normal bite position all molars must strike together evenly creating an uniform application of bite force down on to your ridge.
- Correct vertical placement of teeth. Teeth that are placed too high off a lower ridge will create more leverage to rock the denture.
- Dental implants. Although somewhat costly, these may be the only solution for some patients when the first five components have been met and the patient still struggles with retention.
Beyond good lower denture design there really is no substitute for a solid big lower ridge and the ability of a patient to adapt well.