Abstract
I n 1956 Jorgensen’ first tested the relationship between retention and convergence angle in cemented complete veneer crowns. He used cones 8 mm in diameter at the base and 8 mm high. The convergence angle varied from 5 to 45 degrees in steps of 5 degrees. Instead of cast crowns, brass caps were used with the same base diameter, cemented with the same brand of zinc phosphate cement. To avoid errors in the cementation pressure, a vent was made in the cylindrical bore of the caps to provide an outlet for entrapped air. The maximum retentive value (81.3 gm/mm2) was obtained with the 5-degree convergence angle. The minimum value (57.4 gm/mm2) was with 45 degrees. At 10 degrees the retentive value was 41.4 gm, just about half that at 5 degrees. The relation between retentive force and convergence angle was found to be a hyperbola (Fig.
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