Background: The platform switching (PS) concept refers to the discrepancy between smaller diameter prosthetic abutments related to implant platform diameter and clinically seems to prevent the crestal bone loss and maintain soft tissue levels. However, it is well-known the lack of well-designed prospective randomized clinical trials evaluating the efficacy of platform switching versus platform matching (PM) placed in partially edentulous mandibles. Aim: The purpose of this five-year prospective randomized multicenter study was to assess the differences in bone level changes and success rates between CAMLOG® SCREW-LINE implants supporting single crowns in the posterior mandible restored either with PM abutments or abutments with PS. This paper presents interim results obtained up to two years. Material and methods: Patients ≥18 years old missing two or more adjacent teeth in the posterior mandible and with a natural tooth mesially to the most proximal implant site were enrolled in this study. Free end situations were allowed and opposing dentition must be natural teeth or fixed restorations. Following implant placement patients were randomized either in the group for PS or for PM restorations. 67 patients (8 of them split-mouth) with 160 implants followed-up to two years post-loading were included in this interim report. The distance from implant shoulder to first crestal bone contact, at mesial and distal side, was measured with standardized radiographs and statistical evaluation of significant changes in crestal bone levels between the two abutment types over time was performed with a two-sided t-test of means from the parallel group design. Results: The PS group showed a trend for less bone level change at two years post-loading. Conclusions: At two-years post-loading the implants restored with PS abutments appear to preserve the crestal bone more predictably than the implants restored with PM abutments. Schlagwörter: Dental Implant, Platform switching, Platform matching, bone level