Effect of cement space and delayed placement on the seating of crowns luted with Vitremer, Fuji Duet and Dyract Cem

Purpose: To determine the effects of cement space and delayed placement on the post-cementation elevation of crowns luted with two resin-modified glas s ionomer luting cements (Vitremer, Fuji Duet) and a self-curing polyacid-m odified composite resin luting cement (Dyract Gem). Materials and Methods: The investigation was conducted in two parts: (1) A loading apparatus was e mployed to simulate the seating of a crown on a die. Six dies, differing in the amount of cement space allowed from 6-52 mu m, were used. The loading apparatus allowed for a test cement to be placed in the crown, and subseque nt activation of the apparatus lead to seating of the die into the crown. A fter seating, post-cementation crown elevation was measured. The cements Ph osphacap, Vitremer, Dyract Cem and Fuji Duet were used. Each cement was tes ted 10 times at each of the six cement spaces. The post-cementation crown e levation data was analyzed by one- and two-way ANOVA tests, and Tukey's HSD test. (2) The cements Vitremer, Fuji Duet and Dyract Gem, were tested in a similar fashion to Part 1, except activation of the loading apparatus was delayed. Three cement spaces (6, 29 and 52 mu m) and three delay periods (6 0, 120 and 180 seconds) were investigated. Each cement was tested five time s. The post-cementation crown elevation data was analyzed by one- and two-w ay ANOVA tests, and Tukey's HSD test. Results: The amount of cement space p rovided and the cement used significantly affected post-cementation crown e levation (P = 0.001). Where cementation was delayed, post-cementation crown elevation was significantly affected by both the cement used and the amoun t of cement space provided (P = 0.001). Delayed placement of Dyract Cem had no significant effect on post-cementation crown elevation (P = 0.01). Post -cementation crown elevation when Vitremer was used was significantly affec ted by both the amount of cement space and delayed placement (P = 0.01). A 180-second delay in placement of Vitremer resulted in significantly worse p ost-cementation crown elevation (P = 0.01). Seating was not possible 120 se conds after Fuji Duet had been mixed.