Purpose: Short implants are increasingly being used in posterior regions to avoid grafting procedures and their related risks, costs, and morbidity. However, studies focusing on implants measuring less than 6 mm long remain scarce, and the literature does not yet have a definition of the limits inherent with their use. This study attempts to investigate whether extra-short 4-mm implants are capable of receiving a maxillary single crown. Materials and Methods: This study evaluates, through the finite element method, the stress distribution generated at implant lengths of 4 mm and 10 mm caused by different crown heights (10, 12.5, and 15 mm) in the posterior maxilla region when submitted to axial (200 N) and oblique (100 N) loads. Results: The 4-mm implant showed a similar level of performance as that of the 10-mm implant when submitted to the axial load. However, the oblique load proved to be highly detrimental to both implants, inducing stresses of up to three times higher than those achieved in conjunction with the axial load, especially in the surrounding bone and the abutment. Conclusion: The use of 4-mm short implants to support single crowns in the posterior maxilla region may be feasible in habitual conditions; however, the risk associated with significant oblique loads should be mitigated by adopting a mutually protected occlusion approach and using acrylic occlusal devices if necessary. Palabras clave: biomechanics, dental implants, finite element analysis