Rehabilitation of the edentulous patients with osseointegrated implants often represents a clinical challenge. An accurate anti-rotational implant-abutment connection design is essential to avoid screw loosening. Several investigators recommend Paragonâ and Splineä implant systems for oral rehabilitation due to their abutment connection designs, mechanical properties and clinical success. The Unipostä implant system is also employed for its unique counterclockwise screw and cemented abutment design and lower cost. However, its static compressive strength at the implant-abutment interface has not been studied. AIMS: The aims of this study are 1) Compare the static compressive strength at the implant-abutment interface of three different design systems and 2) Describe the implant abutment connection failure mode. Methods: A holding device of stainless steel was designed to align the implants at 30° with respect to the y coordinate axis. A total of sixty-nine specimens were used, twenty-three (23) for each implants system. A computer-controlled universal testing machine (MTS 810) was used to apply a static compression loading, by a unidirectional vertical piston, until failure was achieved. All specimens were evaluated macroscopically and under a 40x magnification stereomicroscope for longitudinal displacement, abutment looseness and screw fracture. Data was analyzed using ANOVA. Results: The mean for Unipost™ system was 392.5 lbs (SD 40.9), for the Spline™ system 342.7 lbs (SD 25.8), and Paragon® system 269.1 lbs (SD30.7). The Unipostä implant-abutment connection demonstrated a statistically significant superior mechanical stability (p 0.009) than Splineä implant system. The Spline™ implant system showed a statistically significant higher compressive strength than the Paragonâimplant system.(p. value < 0.009). Failure Mode: The Unipost™ system consistently broke at the same site, while the other systems failed at different points of the connection. Conclusion: The Unipost™ implant system established a statistically significant superior compressive strength value than the Spline™ and Paragon® systems.