Apical sealing ability of metal versus plastic carrier Thermafil obturators

Sixty straight maxillary canines, 40 straight mandibular incisors, and 40 curved mesial canals of 27 mandibular molars were instrumented and randomly assigned to one of seven groups of 20 canals. Experimental groups were obturated with metal or plastic carrier Thermafil obturators. Control groups were obturated using the lateral condensation technique. An additional group of 20 unobturated curved molar canals served as positive controls. Kerr Pulp Canal Sealer was used in all obturation groups. The presence or absence of apical extrusion of gutta-percha was recorded. Teeth were suspended in black India ink for 2 wk, cleared, and then examined under a dissecting microscope at x20 magnification. No leakage was found in any of the obturated canals, whereas unobturated controls showed total dye penetration. Plastic carrier Thermafil and metal carrier Thermafil groups produced a significantly greater incidence of apical extrusion of gutta-percha compared with lateral condensation groups (p < 0.001). Extrusion for Thermafil groups occurred significantly more frequently in straight compared with curved canals (p = 0.002). The Thermafil groups showed a higher frequency of filled lateral and accessory canals than in the lateral condensation group; however, this was statistically insignificant (p = 0.48).