Compromised posterior maxilla may be quite challenging for the placement of dental implants and may lead to significant treatment issues. Therefore, alternative strategies such as short implants placement to support fixed denture is a reasonable approach. Impact of short implant geometry and dimensions on bone stress fields is investigated insufficiently, though these parameters are the key factors of bone strength/failure as well as eventual bone/implant/denture loss. The research focuses on finite element study of stress distributions in the atrophic posterior maxilla due to three-unit fixed bridges supported by two short plateau implants. 3D models of posterior maxillary bone segment and implants-supporting three-unit fixed bridge were designed and analyzed under vertical and oblique forces considering different bone quality (types III/IV) and varying implant dimensions (4.5,6.0 mm diameter and 5.0, 8.0 mm length). The study used Bicon implant systems and examined insufficient bone with 0.5–1.0 mm bone thickness. Results indicated that in type III bone, stresses induced by the implant-supported bridges were within safe limit, suggesting a high potential for successful functioning. However, in type IV bone, 4.5 × 5.0 mm implant-supported bridge demonstrated higher bone stress levels, raising the risk of its overload and lowering the successful restoration outcome. These results emphasize the importance of attentive bone quality evaluation when planning short implant placement in patients with compromised posterior maxilla. The study also enlightens the need for further investigations of dental implant-supported denture biomechanics to offer valuable insights for optimizing implant design and placement in complex clinical scenarios.