Repair of newly condensed amalgam restorations

This study investigated the tensile strength of the newly condensed amalgam repaired with newly triturated amalgam in different times. A separable plexiglass mold with a dumbbell shape "cavity" was prepared. Amalgam was condensed in the "cavity" and allowed to set for one hour before it was removed from the mold and used for control. Five controls were prepared. Five groups with five samples in each group were prepared. Amalgam was condensed in the first half of the "cavity" and 5, 15, 30, 60 minutes and 24 hours later newly triturated amalgam was condensed in the second half of the "cavity" for the 5, 15, 60 minutes and 24 hour group samples. All samples were allowed to set in the mold for one hour then removed and stored in 100% humidity condition at room temperature for 24 hours. Tensile strength was tested on the Instron testing machine. It was found that when the newly condensed amalgam was repaired in five minutes, it has 84% of the tensile strength and was not significantly different from the controls. When it was repaired in 15, 30, 60 minutes and 24 hours, the tensile strength was significantly lower than the controls and significantly different from the controls.