Comparison of Retention Forces of Different Fabrication Methods of Co-Cr Crowns: Pre-sintered and Milled, Cast and Electroforming Secondary Crowns with Different Taper Angles

To investigate the retention forces of differently fabricated secondary crowns made of Co-Cr alloy and electroforming secondary crowns considering different taper angles. Cobalt-chromium primary crowns with 0°, 1° and 2° taper angles
were fabricated. Secondary crowns were made either by i.) a milling and sintering, ii.) casting or iii.) electro-forming process. Pull-off tests were performed and data were analyzed by parametric statistics (p<0.05). With regard to the different taper angles, Co-Cr milled and cast groups, no impact on retention force was observed. Within the electroforming group, primary crowns with a taper angle of 1° showed a higher retention force than crowns with angles of 0° or 2°. With respect to the secondary crowns, primary crowns with a taper angle of 1° showed no impact on the results. Within the taper angles of 0° and 2°, the electroforming group exhibited lower retention forces than cast or milled ones. In the 0° taper angle group, milled secondary crowns displayed higher values than cast ones.