Introduction: problem statement: different alternatives as fixed and removable rehabilitation exist. However, there are few studies available that analyze the behavior of these prostheses with control of the biological variables such as bone type, location, and type of implants. The objective of this study was to analyze the biomechanical behavior of two mandibular prosthesis designs supported on four implants and the adjacent biological zones. Materials and methods: two mandibular prosthetic designs were modeled on 4 Zimmer TSV implants (Zimmer Biomet) in a bone with type D2 characteristics (Misch) assuming a 75% osseointegration. The first design was an overdenture (OD) with an internal CrCoreinforcing bar, retained with Locator adjustments (Zest Anchors), the second design was a metal-acrylic hybrid (HP) prosthesis in which instead of using the CAD bar / CAM splinting the implants, an internal reinforcing bar was designed in CrCo, the load applied in each model was 400N distributed throughout the prosthesis. Results: the efforts were concentrated mainly in the crestal portion of the peri-implant bone in both designs, the efforts in the trabecular portion were minimal, in the peri-implant bone the greatest effort was presented in OD 20,643 MPa, in the HP design was 11,823 MPa, the efforts in implants were  67.8 MPa, greater in HP than in OD 52,613 and in the prosthesis the greatest effort was presented in HP; (56,046 MPa compared to 41,518 MPa in OD). Conclusions: the functioning of the designs is not the same and they transmit different stresses, but neither of them compromises the biological or prosthetic structures evaluated.