Complete removable appliances cover only the attached mucous membranes of the remaining alveolar crest of the jawbones and the hard palate. If the lower jawbone has atrophy, the non-mobile mucosal surface is reduced, therefore the stability of the prosthesis is compromised. The upper jaw on the palate has a large surface with a tight mucous membrane, so the upper total prosthesis is more stable than the lower denture. Nowadays total lower dentures are made with implant anchorage. Minimum two implants are required.
Partial removable dentures are more stable than the total dentures because they are supported by the remaining few teeth. The denture, in this case, is loading not only the mucous membrane but also the roots of the remaining teeth. Anchorage can be provided by clasps, telescopic crowns or hidden extracoronal attachments or horizontal bars.
If the jaw is edentulous and the patient can not afford fixed appliances, implants may be suitable for supporting and anchoring the denture by ball heads, locators or bars. If four implants are placed in the optimal site connected with metal bars, forming a high-stability unit, it allows the reduction of the palatal surface of the denture, and it is sufficient to extend the prosthesis only to the alveolar ridge. Cleansing this type of removable prosthesis is very important and can be done by special methods.