Abstract : Vertical root fractures (VRF) are considered one of the most dangerous complications that might occur, due to the difficulty in its diagnosis and prognosis. These fractures happen more frequently, particularly after endodontic treatment. Therefore, this study aimed to evaluate the ability of MTA-based sealers in increasing the fracture resistance of endodontically retreated teeth. The study sample consisted of 45 single-rooted and single-canal premolars. All teeth were decoronated, and instrumented up to Protaper F2 (25/8%). Root canals were then obturated using Zinc-oxide and Eugenol (ZOE) sealer and thermal obturation technique. Then retreatment procedures were done using Protaper F3 (30/9%) and all teeth were divided into three equal groups: Group 1 (Experminteal, n=15): root canal were obturated using MTA-based sealer and single cone technique, Group 2 (Positive Control, n=15): root canal were obturated using ZOE sealer and single cone technique, and Group 3 (Negative Control, n=15): without root canal obturation. All teeth were restored with glass ionomer cement and kept in an incubator at 37°C for a week. All samples were placed within acrylic bases and a vertical force was applied using a Testometric machine and the fracture resistance force was recorded. MTA and positive control groups showed better fracture resistance (485.07, 455.72 N respectively) than the negative control group (492.680 N) with a statistically significant difference (p=0.003, 0.013 respectively). However, no statistically significant difference was found between MTA and positive control groups (p=1.000). Based on this in vitro study, the use of MTA and ZOE enhanced the fracture resistance in retreatment root-filled single-rooted premolar teeth.