The effect of multiple layers of die-spacer on crown retention.

: The application of die-spacer to crown preparation dies prior to the fabrication of the cast crown is an acceptable procedure to improve the fit of the restoration. Previous studies have shown that the retention of the restoration will be improved, unchanged, or reduced when an appropriate thickness of die-spacer is used. No studies have determined the effect on retention if excessive die-spacer is used. This study evaluated the effect of increasing die-spacer thickness on the retention of cast full crowns. Cast copings were fabricated on dies coated with either 0, 4, 8, 12, or 16 coats of die-spacer, cemented on the respective teeth, and removed using an Instron Universal Testing Machine. There were no statistically significant differences (P < or = 0.05) between the mean force required to remove the cemented copings. It appears that increasing the application of die-spacer up to 16 coats (151 micrometers) does not adversely affect the retention of cemented cast copings.