Aim: To compare the effect of placing the definitive abutment at the time of implant placement versus at a later stage, on the soft and hard tissue changes around dental implants. Materials and methods: Implants were placed in the posterior maxilla or mandible of partial edentulous patients and they were randomized to receive the definitive abutment at the moment of implant placement, or 6-12 weeks later. Radiographic assessment of vertical bone level changes (RBC) (primary outcome), clinical status of peri-implant tissues, changes in soft tissues margin, papilla filling and patient-related outcomes were assessed 6, 12 and 36 months after loading. Results: 60 implants were placed in 40 patients. In test group 9 single unit and 19 multiple unit were restored and in the control group 12 single and 19 multiple unit. 45.8% of the implants were placed in the maxilla and 54.2% in the mandible. Overall survival rate was of 98,3% at 36 months. A tendency of greater bone loss was observed in the control group over time, being only statistically significant at 6 months. However, between 12 months and 36 months, a slight greater bone gain was observed in booth group. At 36 months the bone loss was 0.94mm vs 0.49mm in control and test respectively. Periodontal clinical parameters (probing depth, plaque and bleeding) did not demonstrate significant differences between groups at any time point. A significant increase in papilla height was observed from loading to 36 months in both groups, with no differences between the groups. Regarding patient-related outcomes, no differences were between test and control. Conclusion: The one abutment - one time concept is associated with less marginal bone loss. Furthermore, peri-implant tissues stability seem to endure in the long term (3 years). Palabras clave: Marginal bone level, one-abutment one-time, implants