Our purpose was to evaluate the occurrence of complications and the degree of bone loss in a cohort of patients treated with fixed prostheses supported by immediately loaded dental implants. The primary aim was to compare partial versus full-arch fixed dental prostheses. We then tested the effect of sinus lifting. In the present retrospective cohort study, the patients had their implants restored with fixed dental prostheses supported by dental implants positioned in the posterior maxilla and mandible. When necessary, the maxillary sinuses were grafted with particulate autogenous bone. Patients were then ranked according to the following predictors: length of prosthesis, crown-to-implant ratio, number of crowns to number of implants ratio, and presence of sinus lifting. Outcomes were evaluated for up to 2 years regarding the peri-implant marginal bone loss and implant/prosthesis survival rates. Fifty-eight subjects (209 implants) were rehabilitated with 25 fixed full-arch prostheses and 33 partial fixed dental implant bridges (16 supported by implants placed in grafted sinus). The mean marginal bone loss for implants supporting partial fixed dental prostheses amounted to 0.81 mm, whereas that for implants within the group of full-arch fixed dental prostheses was 1.21 mm; the comparison of the levels in the 2 groups showed a significant difference ( P = .0055). A statistically significant difference ( P = .0006) was found between the bone loss around maxillary implants (1.53 mm) and the bone loss around mandibular implants (1.10 mm). Two implants and 4 prostheses failed; 2-year survival rates of partial and of full-arch fixed dental prostheses, respectively, were 94.1% and 96%. Bone loss in full-arch prostheses appeared to be higher than in that of partial prosthesis. Implant-supported prostheses in the maxillae exhibited a bone loss higher than that registered in mandibles.