With complete arch implant prostheses for edentulous patients, the retentive mechanisms for overdentures and the underlying metal frameworks for fixed complete dentures can be visible through the denture base resin, producing an undesirable esthetic result. Ideally, the retentive mechanism for overdentures should be positioned so it cannot be seen through the visible portion of the denture base, does not interfere with proper positioning of prosthetic teeth, and does not excessively enlarge the denture base.
Because of the potential for implant overdentures to fracture under occlusal loading when the bases are relatively thin, metal reinforcing meshworks are sometimes used. These meshworks can discolor the prosthesis, and one study of maxillary implant overdentures noted that three patients did not like the esthetic result achieved in the prosthesis because the base metal reinforcing meshwork cast a gray color through the resin base.10
The same type of discoloration can occur from the metal framework of a fixed complete denture discoloring the overlying pink denture base resin (Figures 25A, 25B). Also, leakage between the denture base resin and metal over time can create staining.
The metal visibility through the resin and the discoloration from leakage can be reduced or eliminated by bonding an opaque resin to the metal framework of a fixed complete denture or the reinforcing meshwork of an overdenture before the denture base resin is processed to the prosthesis.