Background: The platform switching concept refers to the discrepancy between smaller diameter prosthetic abutments related to implant platform diameter. Clinically, the application of such components seems to reduce marginal bone resorption and to maintain soft tissue levels improving treatment outcomes and patient satisfaction. Up to this date the literature is sparse on long-term results deriving from well-designed randomized controlled trials evaluating the efficacy of platform switching versus platform matching. Aim: The purpose of this five-year prospective randomized multicenter study was to compare the clinical performance and peri-implants marginal bone levels of implants restored with platform switching (PS) or platform matching (PM) abutments. Materials and methods: The study enrolled adult patients missing two or more adjacent teeth in the posterior mandible mesially bounded by a natural tooth. Patients underwent open flap implant insertion and were randomly allocated to the PM or PS group, receiving the corresponding healing abutments. Loading was carried out after a healing period of 6-12 weeks (and for bone quality IV 12-18 weeks) with cemented crowns. Patients were followed annually for 5 years. Outcome measures were marginal bone level changes, implant survival and clinical parameters plaque index, sulcus bleeding index and pocket probing depth. Results: Thirty-three patients received 72 implants in the PM group and thirty-five patients received 74 implants in the PS group. Sixty patients attended the final appointment of the study, 31 had received PS components and 29 had received PM components with 65 and 63 implants respectively. Estimated mean difference in marginal bone levels of PS and PM restored implants was 0.28mm (95% CI: [0.06, 0.49], p=0.011), favouring the switching components. After 5 years the overall survival rate was 96.6% with no differences between groups (p=0.647). Conclusion: Patients requiring implant supported restorations in healed bounded or free end edentulous gaps of the mandible benefit from the use of PS prosthetic components from the surgical procedure onwards. Schlagwörter: Dental Implant, platform switching, platform matching, bone level, marginal bone loss