The effectiveness of pins with complete cast metal crowns

Abstract

T he basic retentive elements in complete cast metal crown preparations are height, convergence, and surface area. Surface roughness of the casting and the cavity walls also contributes to retention, but to a lesser degree. Adhesive strength of the cementing medium aids retention, but this depends on the choice of product. Adequate retention form is difficult to attain for short, malpositioned, and malformed crowns. Auxiliary retention with cement keys for such crowns is effective.’ Cement keys are not widely used, probably because of lack of familiarity with the technique. Nevertheless, short, malpositioned, and malformed crowns are a fairly common problem in dental practice. An effective, common, and convenient technique is needed to increase the retentive strength of abnormal crowns. The purpose of this study was to examine the effectiveness of the use of pins to increase the retention of crowns. testing machine. After thoroughly cleaning the crowns and teeth, the crowns were cemented to the preparations with zinc phosphate cement (Mizzy, Inc., Clifton Forge, Va.) according to the manufacturer’s directions. After initial setting of the cement (5 minutes), all samples were stored in 100% humidity at 37” C for 24 hours. Retentive strength was tested with the Instron Universal Testing Machine (Instron Corp., Canton, Mass.) at a crosshead speed of 0.5 cm/min.