The aim of this study was to investigate whether endodontically retreated teeth filled with Resilon are more resistant to fracture than those filled with guttapercha following hand or rotary removal techniques. Seventy-two upper anterior human teeth were selected, decoronated and reduced to 12 mm. The canals were shaped using rotary ProTaper files and randomly assigned into two groups (n=36). Obturation was performed using guttapercha/AH-Plus in Group 1 and Resilon/RealSeal in Group 2. The roots were stored for one week at 37°C. The roots were then randomly allocated into three subgroups: A (n=10), no further treatment was performed. In B (n=13), the filling was removed using hand K-files and in C (n=13) using ProTaper retreatment files. Subgroups B and C were refilled using the same materials as used in the primary treatment and stored for one week. Three roots from each of the four subgroups were left unfilled to act as a control (n=12). All the roots were embedded in resin and subjected to fracture in a universal testing machine. Data were analysed using Kruskal-Wallis with multiple pairwise comparisons. Resilon-refilled roots showed no significance difference in fracture resistance compared with guttapercha-refilled roots regardless of the retreatment technique. There was no significant difference in fracture resistance between the two retreatment techniques. When used as a root filling material, Resilon was found not to increase the fracture resistance of primarily and previously root filled teeth regardless of the retreatment technique.