Objectives: Biomechanical load-fatigue performance data on single-tooth implant systems with different implant-abutment interface designs is lacking in the literature. This study evaluated the load fatigue performance of 4 implant-abutment interface designs [Brånemark-CeraOne (BR) – external hexagon; Replace Select-Easy abutment(RP) – cam tube; 3i Osseotite-STA abutment(3i) – external hexagon; and Lifecore Stage-1 –COC abutment system(LC) – cone screw]. The number of load cycles to fatigue failure of 4 implant-abutment designs was tested with a custom rotational load fatigue machine. The effect of increasing and decreasing the tightening torque by 20% respectively on the load fatigue performance was also investigated. Methods: 3 different tightening torque levels (recommended torque, -20% recommended torque, +20% recommended torque) were applied to the 4 implant systems. There were 12 test groups with 5 samples in each group. The rotational load fatigue machine subjected specimens to a sinusoidally applied 35Ncm bending moment at a test frequency of 14Hz. The number of cycles to failure was recorded. A cut-off of 5 x 106 cycles was applied as an upper limit. Results: There were 2 implant failures and 1 abutment screw failure and in the BR group. 5 abutment screw failures and 4 implant failures was recorded for the 3i system. The RP system had 1 implant failure. 5 cone screw failures were noted for the LF system. ANOVA revealed no statistically significant difference in load cycles to failure for the 4 different implant-abutment systems torqued at recommended torque level. Statistically significant difference was found between the –20% torque group and the +20% torque group (p<0.05) for the 3i system. Conclusions: We conclude that there was no statistically significant difference between the 4 implant-abutment systems torqued at the manufacturers' recommended torque level. The manufacturers' recommended torque level should be adhered to the 4 implant-abutment systems for predictable results. Supported by NUS Research Grant R-224-000-012-112