Mobile Prosthesis (Combined or Complete Denture) can be an alternative to fixed prosthesis on implants in cases when there is a need to replace a group of missing teeth and it is not possible to replace them with a bridge (the teeth around are not steady enough to hold a bridge). This solution is much less difficult to implement and also is more economical.
The partial denture is used to replace a group of missing teeth (even if they are not in a row). It is hooked onto existing teeth and takes advantage of edentulous gum using it as a cushion for the “fake” gum and teeth of the prosthesis. Most of the mastication force is amortized (absorbed) by this cushion thus avoiding the overload of the remaining teeth.
The dimensions of the mobile prosthesis depend on the structure. The prosthesis entirely of acrylic are quite voluminous and “steal” more space in the mouth, but are cheaper and allow you to easily add more teeth if necessary. The prosthesis with internal metal structure , “with skeleton”, have much smaller dimensions (often it is a very thin bar lying on the palate in case of upper prosthesis, or a curved bar that runs behind the incisors in case of lower prosthesis).
Complete dentures are used when all teeth are missing.
Complete upper denture is retained in place due to a so-called “suction effect”: covers the whole palate and the gums covering the bone ridge of the upper jaw, making an air-tight zone (vacuum). The larger is the air-tight surface the better is retention. However, in some cases the back border of the denture needs to be shortened (when a patient has a high gagging reflex).
Complete lower denture is more difficult to retain in place as there is no possibility to create a large air-tight zone and the lower jaw is the mobile bone (we move it constantly when speaking, eating, swallowing). It is retained mainly by the muscles of the lips, cheeks and the tongue.
However, unfortunately, after many years the edentulous bone reabsorbs and the ridge provides always less retention. For this reason it is advised to adjust the mobile prosthesis once in two or three years.
Today there is another modern solution to retention of mobile prosthesis – retention on implants. In this case two or four implants (in case of lower jaw) are placed in the bone ringe. These implants are further used as “hooks” to hold the denture in place.