An In Vitro Study Of Root Canal Obturation Of C-Shaped Canals In Mandibular Second Molars By Three Techniques

Objective: To compare the sealing ability and marginal adaptation of three obturation techniques when used in c-shaped canals of mandibular second molars, and to investigate the filling efficiency of three obturation techniques in the c-shaped canals. Methods: Twenty-four extracted mandibular second molars with fused roots were selected. The teeth containing c-shaped canals were randomly divided into three groups, instrumented using Protaper^TM series in crown-down technique, the canals were filled using three different techniques: Obtura II (group A), cold lateral condensation (group B) and Thermafil (group C). Then, voids, obturated lateral canals and reticular apical triangles on the X-ray were counted. After dyeing for 7 days in the ink, dyeing lines were measured to reflect the microleakage. The percentages of gutta-percha, sealer and gaps on the root canal surface were determined by analyzing the images of 3 sections per tooth. Data were analysed using chi square test or LSD-t test or Kruskal wallis test. Results: There is a high prevalence of c-shaped canals in mandibular second molars with fused roots (87.5%). The reticular apical triangles were most frequently observed in Thermafil (P < 0.05). Dyeing lines of cold lateral condensation had an average length of 1.47mm, which was significantly different from that of Obtura II (0.97 mm) and Thermafil (1.07 mm), P <0.01. The percentage of gutta-percha of Thermafil is significantly higher than that of the Obtura II and cold lateral condensation on the root surface of the middle and apical sections, while the percentage of sealer of Thermafil is lower than the other groups on these two sections(P < 0.05). Obtura II have the lowest percentage of gaps on the middle section (P < 0.05).