Purpose: To compare the clinical and radiological outcomes of identical implants with conical or internal hex connections. Methods: A total of 90 patients with partial edentulism requiring one implant-supported prosthesis were randomly allocated in two equal groups (n = 45) to receive either implants with a conical connection or implants of the same type, but with an internal hex connection at three centres. Patients were followed for 1 year after loading. Outcome measures were implant failures, any complication and marginal bone level changes. Results: One patient (2.2%) belonging to the internal hex group dropped out. One implant (2.2%) failed in the conical group. There were no statistically significant differences in implant failures between the two groups (2.2% vs. 0%, difference 2.2; 95% CI: -1.3; 5.7; P = 0.315). Two complications occurred in the conical group and two in the internal hex group (P = 1.000, difference 0.00, 95% CI: -3.1; 3.1). The 12-month peri-implant bone resorption was similar in both groups: 0.56 ± 0.53 mm (95% CI 0.03; 1.09) in the conical group and 0.60 ± 0.62 mm (95% CI 0.02; 1.22) in the internal hex group (difference = 0.04 ± 0.55, 95% CI: -0.51; 0.59, P = 0.745). Conclusions: Within the limitation of this study, preliminary short-term data (1 year post-loading) did not show any statistical differences between the two internal connection types, therefore clinicians could choose whichever connection they prefer.