Aim To compare the interfacial strength and failure mode of root fillings consisting of different technique-material combinations. Methodology Human mandibular premolars (n = 144) instrumented to apical size 40 and.06 taper were divided into 12 experimental groups. The root canals were filled with either gutta-percha (groups 1-6) or Resilon (groups 7-12) core materials combined with AH Plus (groups 1, 4, 7, 10), Ketac-Endo (groups 2, 5, 8, 11) or Epiphany (groups 3, 6, 9, 12) using cold lateral compaction (groups 1-3, groups 7-9) or System B with Obtura II (groups 4-6, groups 10-12). Three serial 1.00 ± 0.05-mm-thick root slices were prepared and push-out tests on the filling material were performed. Interactions amongst the compaction techniques, core materials and sealers were analysed using a three-way analysis of variance (anova) (P < 0.05). One-way anova and Duncan's Multiple Range tests were used to compare the bond strengths of the 12 groups. Fracture modes of all root slices were evaluated stereomicroscopically at ×40 magnification. Results All the parameters except compaction techniques had significant interactions (P < 0.05). A significant difference was found amongst the groups (P < 0.05). Gutta-percha/Ketac-Endo/cold lateral compaction and gutta-percha/AH Plus/cold lateral compaction groups had the highest micropush-out bond strength values (P < 0.05). The number of overall cohesive failures was significantly more than that of adhesive failures (P < 0.05). Conclusions The push-out bond strengths of Resilon/Epiphany combinations were lower than those of gutta-percha/ conventional root canal sealer combinations. Core materials and sealers may affect the push-out bond strengths of root canal filling materials. © 2007 International Endodontic Journal.