Study of the Effect of Die Spacing (Cement Space) on Cast Crown Retention

Cement space is necessary for seatabillity and fittness of cast crowns, but can affect crown’s retention. In this study the interrelationship between them was investigated via die spacing.

For evaluating the effect of die spacing (cement space) on crown retention after cementation, 50 similar machined metallic dies were prepared and divided into five groups and coated with 0.2,4,6,8 layers of paint-on standard die spacer, respectively. Cast crowns were fabricated on the dies using base metal alloy’s, and then cemented with zinc phosphate cement under a constant load of 5 kg for 10 minutes. The samples were started in distilled water for 48 hours. Then the force required to remove each crown from the die was measured with instron.

Statistical analysis revealed a significant increase in the force required (crown retention) by adding layers of die spacer (p<0.05).

Because retention didn’t show any significant increase with more than 4 layers of die spacer, so optimum thickness of die spacer (or cement space produced) is suggested to be 4 layers equal to 40 microns.