["To evaluate the clinical performance as well as patients' and clinicians' satisfaction on two different prosthodontic retention systems for implant-overdentures in the mandible.", "In this retrospective study, patients provided with four intraforaminal implants with at least 12\xa0months of follow-up since overdenture delivery were evaluated. A total of 39 patients were treated either with Locator(®) attachment or with cad-cam milled bar. Clinical parameters such as Peri-implant Probing Depth (PPD), Plaque Index (PI), and Bleeding on Probing (BOP) were evaluated. Patients' and clinicians' perceptions regarding the outcome were assessed on visual analog scales (VAS).", "The mean follow-up was 13\xa0months in the Locator(®) group and 18\xa0months in the Bar group and no implants were lost. The Locator group showed better results for PPD, PI, and BOP values. Patients' satisfaction was high in both groups, whereas the clinicians found better hygienic conditions and soft tissue health in the Locator group."] Do single unit attachments improve peri-implant soft tissue conditions in mandibular overdentures supported by four implants?