Abstract: Objective To measure the fatigue test system designed by ourselves, and evaluate the fatigue strength of root filled by cold lateral condensation and warm vertical condensation. Methods 20 lower premolars were made by access cavity and root canal preparation, and then divided into 2 groups randomly. Group A was cold lateral condensation, and group B was warm vertical condensation. After condensation the teeth were cut down the crown along the cemento-enamel junction. Specimens were subsequently submitted to an axial compression cycle test with 50 N, 2 Hz in fatigue test system, until fractured. The cycle time was recorded. Total values were analysis by t-test. Results The average load frequency of cold lateral condensation was 16 402.00±4 632.57, and warm vertical condensation was 16 500.00±4 558.37. The results from t-test revealed that there was no difference between two groups（t=0.96, P＞0.05）. Conclusion The fatigue test system designed by ourselves
could imitate the bite cycle. And it could be concluded that the fatigue resistance between cold lateral condensation and warm vertical condensation had no difference.

Key words: vertical root fracture, fatigue strength, root canal therapy