The impact of abutment- or implant-level fixed partial dentures on marginal bone level around implants in vertically thickened soft tissues: a 1-year follow-up randomized clinical trial.

PURPOSE: This study evaluated phase-specific peri-implant marginal bone level (MBL) changes associated with abutment disconnection and reconnection during prosthetic procedures by comparing implant-level (IL) and abutment-level (AL) restorative protocols over a 1-year period. METHODS: This two-arm randomized controlled clinical trial included patients receiving posterior mandibular fixed partial dentures following soft tissue augmentation. Implants were randomly assigned (1:1) to IL or AL protocols. In the IL group, repeated abutment disconnection and reconnection were performed during prosthetic procedures, whereas in the AL group, a definitive abutment was connected and maintained without disconnection. Standardized periapical radiographs were obtained at implant placement (T0), 2 weeks after second-stage surgery (T1), at definitive prosthesis delivery (T2), and 1 year after loading (T3). MBL changes were analyzed by phase: suprastructure connection (T1-T0), prosthetic (T2-T1), maintenance (T3-T2), and cumulative (T3-T0). Statistical significance was set at P<0.05. RESULTS: Implant success was 100% at 1 year in both groups. In the IL group, MBL changes were Δ(T1-T0)=-0.41±0.43 mm, Δ(T2-T1)=-0.34±0.38 mm, and Δ(T3-T2)=-0.31±0.43 mm, with a cumulative change of Δ(T3-T0)=-1.06±0.49 mm. In the AL group, the corresponding values were -0.81±0.44 mm, -0.14±0.24 mm, -0.12±0.30 mm, and -1.08±0.39 mm, respectively. Phase-specific remodeling differed between protocols, whereas the cumulative 1-year change was comparable. CONCLUSIONS: Under conditions of vertical soft tissue augmentation, abutment disconnection and reconnection were associated with phase-specific MBL remodeling; however, cumulative 1-year MBL changes were similar between IL and AL protocols.