Effect of Seating Force, Margin Design, and Cement on Marginal Seal and Retention of Complete Metal Crowns

Purpose: The purpose of this study was to determine the marginal discrepancy and retention of silver-palladium crowns cemented with zinc phosphate (Phosphacap) and glass-ionomer cement (Fuji Cap 1) using different seating forces on preparations with various margin designs. Materials and Methods: Crown preparations with three finish lines-chamfer, shoulder, and shoulder with a 45-degree bevel-were sequentially prepared on a dentoform premolar. A metal die for each of the three finish lines was constructed. Complete metal crowns were fabricated for each metal die using a silverpalladium alloy. Three different seating forces-25, 100, and 300 N-were used to load the crowns until initial set of the cement. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using a digimatic indicator. Retention was determined by measuring the tensile strength using the Lloyd universal testing machine. Results: The higher seating forces produced better crown seating but had no significant effect on crown retention. The shoulder and shoulder with bevel finish lines provided better crown retention than the chamfer. Glass-ionomer cement provided greater crown retention than zinc phosphate cement. No significant correlation between marginal seating and crown retention was revealed using a Pearson analysis. Conclusion: Marginal seal was not influenced by either margin design or type of luting cement, but was improved with higher seating force. Crown retention was affected by the margin finish line and the luting agent.