A new approach to partial denture design for unilaterally remaining lower teeth

Abstract

The usual types of removable partial dentures do not function adequately in mouths where one or a few lower teeth remain on only one side and where there are edentulous regions anterior and posterior to the teeth. The amount of rotation around framework fulcrums of sections of the denture base varies greatly. This uneven movement may cause excessive resorption of the ridge on the side opposite the remaining teeth. Fulcrum points or areas of the framework on a horizontal plane must be eliminated to permit a uniform vertical movement of the base. This objective can be accomplished by eliminating occlusal rests and the engaging points of stress-breaking devices. The natural tooth contours are modified by crowns to allow continuing contact of the framework and abutment teeth during function and following ridge resorption. Crowns placed on abutment teeth are contoured to have surfaces 4 to 5 mm. long that are parallel to each other in a vertical direction. These surfaces are contacted by metal bands that encircle the crowns. The contacts are 0.5 mm. in diameter, and they are made at the center of the 2.5 mm. wide metal bands. Space is established 1 mm. occlusal to and gingival to the area of contact. This space permits rotation without causing excessive torque on the abutment teeth. Contact is established after the initial rotation. The amount of space is determined by such clinical factors as the condition of ridges, crown heights, root lengths, and periodontal evaluation of the remaining teeth. The crowns may be constructed of gold or porcelain on metal. No attempt is made to attain primary retention. Occlusal displacement is counteracted by the stabilizing effect of the framework and patient training in proper tongue position. Since this type of prosthesis functions similar to a complete denture, it should be constructed only in conjunction with a complete upper denture. Acrylic resin teeth are used on the upper denture and porcelain teeth on the lower one. The teeth of the upper denture that oppose the crowns are set out of contact. Dentures of this type were constructed for 19 patients over a 2 year period. Observations on the patients were made at 6 month intervals. The observations were on patient reaction, tissue condition, stability, periodontal condition and mobility of abutment teeth, retention, maintenance of occlusion, and ridge resorption. The results were generally favorable with good patient acceptance and satisfaction. The long-term potential of the procedure requires further clinical study and observation. Information on length of time that abutment teeth can be retained, the magnitude of ridge resorption, and the relationship of ridge resorption to tooth extrusion must be secured before a final evaluation of the procedure can be made.