Comparing of retention of cast crowns cemented with two kind of permanent cement with and without prier use of temporary cement

摘要

Introduction: This study evaluated the effects of eugenol –free temporary cement remnants on theudretentive strength of casting crowns luted via zinc phosphate and resin cement (Maxcem) to theudtooth structure.udMaterial and methods: 40 extracted human molars ware randomly divided into 2 groups. eachudgroup was then divided into 2 subgroups and the teeth were paired so that the size of each tooth inudeach subgroup was the same as a tooth in the other subgroups. 40 standardized Ni-cr completeudcrowns were made on teeth prepared with a milling machine using conventional laboratoryudtechniques. For each adhesive system, in one subgroups a provisional restoration was cementedudusing an eugenol –free temporary cement. Temporary crown was remained on the tooth structureudfor an hour and then extracted and cement remnant was removed by an excavator. Then the casingudcrowns were adhesively luted via zinc phosphate, adhesive resin(Maxcem) to prepared teeth. Afterud24h storage in distilled water, Retention was evaluated by measuring the tensile force required touddislodge the crowns from tooth preparations with a universal testing machine after thermo cyclingud(1500 cycles between 5c and 55c with 1- minute dwell times). The data were analyzed by means ofudpaired T-test and wilcoxon test in SPSS software version 11.5udResults: The analysis showed the mean retentive strength for 2 subgroups with and without prioruduse of temporary cement in the maxcem group was 176 ± 55 and 274 ± 169 N, there was not audsignificant difference between the 2 subgroups. (p value = 0.174). And the mean retentive strengthudfor 2 subgroups with and without prior use of temporary cement in the zincphosphate group wasud257 ± 125 and 238 ± 135 N, there was not significan t difference between the 2 subgroups (p valueud= 0.782).udDiscussion: The use of an eugenol –free temporary cement does not alter the retentive strength ofudcasting restorations lutted to prepared teeth using the tested adhesive system, when temporaryudcements are removed properly.