2.8. Stereomicroscopic Analysis of Dye Penetration
tooth
BLIND
All experimental group samples were evenly coated with two layers of colored nail polish, with the exception of their apical 2 mm. The negative controls were entirely coated with nail polish (including their apical foramen), whereas positive control samples did not receive any nail polish application. Following complete drying of nail polish, the samples were vertically placed in 0.2% rhodamine B (Avonchem, Macclesfield, UK) dye solution for 48 h. They were then rinsed under running tap water and air dried.Nail polish and dye was scraped off the samples using a #15 surgical blade to prevent dye introduction onto the inner root surface at the time of sectioning. The roots were split longitudinally parallel to the long axis of the tooth. To ensure that the sectioning was performed through the center of the root, 2 mm deep longitudinal grooves were made in the middle of the buccal and lingual root surfaces using a diamond disk in a slow-speed handpiece, with caution taken not to invade and damage the canal space. The teeth were then fractured longitudinally with a double-tapered chisel and mallet, preserving the entire obturation space [A random sequence of the samples was generated via computer software (MS Excel) and allocated to subgroups. The samples were viewed under a stereomicroscope (Olympus VM-ILA-2) at 40× magnification. The images were captured and uploaded to IMAGE J software (National Institute of Health, Bethesda, Maryland, USA) and blind analyzed by two examiners. For assessment of apical microleakage, investigators measured the linear depth of dye penetration by recording the maximum distance traveled by the dye from the root apex up to its coronal extent at the sealer–dentinal wall interface. All measurements were calculated in millimeters (mm).