Introduction When dental implants are installed and subjected to functional loads, marginal bone resorption is frequent, also in sites not affected by peri-implantitis, and it can be a critical factor that will affect the aesthetics and longevity of the implant because it is associated with an increased risk of peri-implantitis and soft tissue collapse. Objective To assess the peri-implant marginal bone loss and the survival percentage of implant restorations that present internal and external prosthetic connections. Material and methods A systematic review of the literature was carried out. Various information sources were consulted such as PubMed, Embase, Ovid, Scopus databases. For the search process, the methodology approved by the PRISMA Guide was followed. Results 5 articles were found that met the established criteria. In these articles, 2,866 patients rehabilitated by means of 6,455 implants were registered, of which 3,057 were restored with an external hexagonal prosthetic connection and 3,398 with an internal connection of the hexagonal or conometric type. The 3,057 implants prosthetized by connection to an external hexagon showed a mean peri-implant marginal bone loss of 0.986 ± 0.58mm. The 3,398 implants prosthetized by means of an internal hexagon or conometric type connection highlighted a mean peri-implant marginal bone loss of 0.86 + - 0.43mm. Conclusion Taking into consideration the individual characteristics of each patient and each situation, the literature seems to indicate that on the intensity of the mechanical stress and the tensions emitted to the peri-implant region, the conical connection and the cylindrical design of the implant transmit less stress to the cortical bone. Bone with respect to the external hexagonal connection and the conical design of the implant, which transmit less stress and tension to the trabecular bone and more to the cortical bone.