Introduction: Multi-stranded wires are superior to conventional wires in the fixed lingual retention after orthodontic treatment. The impact of the cross-section of those wires on its efficacy was not studied before. Aim: The aim of the study was to measure forces generated by multi-stranded lingual fixed retainers and comparing rectangular to round wires. Materials and Methods: A simulation model of the Orthodontic Measurement and Simulation System (OMSS) was used to measure the force generate in 15 rectangular and 15 round soft dead fixed lingual retainer wires on orthodontic stone models. The resistance was recorded after subjecting wires to gradual displacement in both load and unload directions, and horizontal and vertical axes. The movements were in 0.02 mm increments to simulate the normal physiological tooth movement. Results: In the load direction and horizontal axis, resistance increased proportionally with displacement in the rectangular and round wires from 0.58-5.62 N and 0.32-1.65 N, respectively. In the vertical axis, resistance increased proportionally with displacement in the rectangular and round wires from 0.82-7.68 N and 0.24-1.72 N, respectively. Through the whole range of the studied displacement, the recorded resistance was significantly higher in the rectangular wire. The resistance generated in both axes was significantly (P<0.0001) dependent on the type of the wire followed by the displacement then the interaction between them. Those findings were confirmed in the unload direction. Conclusion: In addition to the superiority of the rectangular wire to the round type in fixed retention, it allows teeth movement in the physiological range.