Background: The purpose of this clinical study was to evaluate the complications associated with the different attachments used in implant-supported overdentures, including prosthetic problems and implant failures. A comparison of ball, bar and Locator (Zest Anchors, Inc, homepage, Escondido, CA, USA) attachments, in completely edentulous patients with two, three or four implants, was conducted. Material and methods: A total of 36 edentulous patients (20 female, 16 male) with a mean age of 66.3 years, were enrolled in the study. The patients were treated with 95 implants, for the prosthetic restoration of the maxilla or the mandible. The mean follow-up time was 41.17 months. Prosthetic complications including, fractured overdentures, replacements of O-ring attachment and retention clips, implant failures, hygiene problems, mucosal enlargements, attachment fractures, retention loss and dislodgement of the attachments were recorded and evaluated. The recall visits at 3, 6, 12 months and, annually thereafter. Results: Fourteen complications in the ball attachment group and 7 complications in the bar group were observed. No complications were observed in the locator group. The difference was found to be as statistically significant (p=0,009). Six of the 95 implants had failed. Totally 39 implant overdentures were applied. Three prostheses were renewed because of fractures. Conclusion: Within the limits of the present study, it was concluded that the locator system showed superior clinical results than the ball and the bar attachments, with regard to the rate of prosthodontic complications and the maintenance of the oral function. © Medicina Oral S. L.