Effect of Immediate and Delayed Post Space Preparation on Apical Leakage Using Three Root Canal Obturation Techniques After Rotary Instrumentation

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For teeth that have undergone root canal therapy post fabrication and subsequent crown restoration are often required to increase strength. It is necessary to remove a portion of gutta-percha during post space preparation that may cause displacement of the root canal fillings and affect their sealing ability. This study evaluated the effects of different post space preparation time intervals and root canal obturation techniques on the apical sealing ability of filled root canals. One hundred single-canal teeth were incrementally crown-down enlarged to an apical diameter of 0.40 mm with 0.06 taper by K3 rotary instrumentation, combined with 5.25% NaOCl irrigation. The teeth were randomized into four groups: 30 obturated by lateral compaction technique (Group 1); 30 by vertical compaction technique (Group 2); 30 by injectable thermoplasticized gutta-percha technique (Group 3); and 10 controls with no obturation (Group 4). All specimens were stored in 100% humidity at 37°C. Immediately and 3 days and 7 days after obturation, post space was made utilizing heated pluggers, and leaving a 5.0-mm gutta-percha filling. The teeth were immersed in 2.0% methylene blue solution for 72 hours, and finally cut longitudinally in half. Dye leakage was examined under a stereomicroscope. The results were recorded and statistically analyzed. The mean distance of dye leakage after post space preparation at three different time intervals in Group 1 were greater than those in Groups 2 and 3. One-way analysis of variance indicated that the apical seal or adaptation of vertical compaction technique and injectable thermoplasticized gutta-percha technique were not easy to break during post space preparation. Teeth treated by vertical compaction and injectable thermoplasticized gutta-percha techniques showed less leakage than those treated by lateral compaction. The least amount of dye leakage existed when the post space preparation was made on day 7 after root canal obturation.