Influence of Sealer Placement Techniques on Void Formation in Flattened Root Canals Obturated with BC Universal Sealer: A Laboratory Study

This study evaluated the influence of different sealer placement techniques on void formation in flattened root canals obturated with BC Universal Sealer using the single-cone technique. Thirty-six extracted human mandibular premolars with flattened canals were randomly assigned to four groups (n = 9): syringe delivery alone, syringe delivery with indirect ultrasonic activation (IUA), direct sonic agitation (DSA), or Lentulo spiral placement. All canals were prepared to size 35/0.06 and obturated with BC Universal Sealer and a matched gutta-percha cone. Voids were assessed by two blinded examiners using radiographs and cross-sections at 3, 6, and 9 mm from the apex. Lower scores indicated fewer voids. Data were analyzed using the Kruskal–Wallis and Dunn’s post hoc tests (α = 0.05). Radiographic analysis showed significant differences among groups (p < 0.001), with IUA producing higher void scores than DSA and Lentulo placement (p = 0.001). Cross-sectional analysis revealed significant differences in the coronal (p = 0.006) and middle thirds (p = 0.009), but not in the apical third (p = 0.083), with IUA again showing more voids than DSA and Lentulo. No technique differed significantly from syringe delivery alone. Within the study limitations, DSA and Lentulo placement yielded fewer voids than IUA.