Isfahan University of Medical SciencesDental Research Journal1735-33271120080113In vitro Determination of the Least Length of Gutta- percha Necessary for Establishment of Apical Seal After Post-Space Preparation.44SB.Mousavi. drj@dnt.mui.ac.irA.HavaiM.Bolbolian20101106Determination of the least length of gutta-percha that is necessary for apical seal after post space preparation. Introduction: After root canal therapy, restorative treatment is necessary. Therefore pinhole or post space prepara- tion is made by removing the coronal parts of gutta-percha. The aim of this study was to determine the least length of gutta-percha that is necessary for apical seal after post space preparation. Meterials and methods Total of 87 single extracted teeth with no abnormal condi- tion were studied. The samples were pre- pared and their canals were obturated and sealed. AH26 sealer was used. Experimental groups were divided into three groups of 3, 5 and 7 millimeters of remaining gutta-percha. Post space was repared one week later. The whole length of the roots except for the three millimeters of apical was sealed with cyanoacrylate glue and nail polish. The samples were placed in penicillin vial that contained sterilized cultural media (TSB). Human saliva was injected twice a day. Data collection was made by inspection and registration of turbidity in cultural media daily. Dataobtained from this study was subjected to one-way Anova test. Results There was no significant difference between the experimental groups. Conclusion 3 millimeters of remaining guttapercha with AH26 sealer is the least length that is necessary for apical seal after post space preparation. Key words apical seal, post pace,human saliva, and microleakage.