Dimensional accuracy and retentive strength of a retrievable cement-retained implant-supported prosthesis

The purpose of this research project was to compare the fit of a retrievable cement-retained implant-supported framework to that of a traditional wax and cast, screw-retained framework and to test the strength of the cemented restoration. Ten telescopic frameworks were luted to gold cylinders with a bis-GMA resin cement. The control group consisted of 10 frameworks fabricated with traditional wax and casting techniques directly to the gold cylinders. Frameworks were analyzed for distortion in the z-axis using scanning electron microscopy and a single screw test. Results demonstrated that the retrievable cement-retained group had a decreased gap distance and improved angular distortion (statistical significance P < .01) compared to the control group. Retentive strength measurements for the cement-retained group with a direct pull-out test revealed a mean pull-out force of 65.7 kg. Three of the 5 samples surpassed the tensile strength of the gold retaining screws (76 kg). Cement-retained restorations demonstrated superior fit in the z-axis and angular distortion compared to traditional wax and cast screw-retained frameworks. Retentive tests support a simplified technique of clinically luting telescopic implant-supported frameworks with adequate retentive strength.