OBJECTIVE To compare the sealing ability and fracture resistance of roots endodontically treated with bonded and unbonded filling materials. METHODS One hundred and fifteen straight mandibular premolar teeth with single canal were divided randomly into 6 experimental groups, with 15 samples each, and 3 control groups. The sealing ability was evaluated using a glucose quantitative microleakage mode and fracture resistance was tested by universal testing machine. RESULTS The microleakage results showed that the bonded filling material had the lowest value while the unbonded filling material had the highest value in all groups. There were significant differences in microleakage value among the groups (P < 0.01), but no significant difference was noted in the fracture resistance among the testing groups (P = 0.7016). CONCLUSIONS Bonded filling material enhanced the sealing ability but could not reinforce the fracture resistance of endodontically treated teeth.