The distribution of stress under implants is affected by several factors. Among others, the implant design affect directly the biomechanical behavior of the implant- prosthesis system. To analyze the effect of implants design on the biomechanical behavior of mandibular ISCP using finite element analysis (FEA). It is a 3-D finite element study using Abaqus software. 2 models were simulated: the first one represents a 4-smooth cylindrical implant-supported prosthesis, the second one is a 4- smooth cylindro-conical implant-supported prosthesis The highest stress value found in the 4CISP model was 545.6MPa. The 4CCISP model showed a very close maximum stress value (561.9MPa). In all models, the highest stress concentration was observed in the dental implants, precisely in the most anterior ones. The flexion of the anterior prosthesis part was observed in the two models. Almost the same stress distribution pattern was observed. Cylindrical implants are more advantageous than the tapered implants, since they offer a better stress distribution and a superior biomechanical behaviour.