Purpose: This 10-year prospective, randomized, clinical trial investigated the treatment outcome of edentulous patients treated with mandibular overdentures retained by 2 endosseous implants compared with conventional dentures in patients with or without vestibuloplasty. Materials and Methods: One hundred fifty-one edentulous patients (5 groups) with a symphyseal mandibular bone height between 8 and 25 mm participated. Sixty-two patients were treated with an overdenture retained by 2 implants (groups 1 and 3), 59 patients were treated with a conventional denture (groups 2 and 5), and 30 patients were treated with a conventional denture after preprosthetic vestibuloplasty (group 4). Patients who received conventional dentures but preferred implants later on could undergo implant surgery after 1 year of their initial treatment, but were analyzed in their original group. The prosthetic and surgical care and aftercare were scored during a 10-year evaluation period. Results: One hundred thirty-three patients completed the 10-year follow-up evaluations. Forty-four percent of patients treated with conventional dentures switched within 10 years to implant-retained overdentures, versus 16% of the patients who were treated with conventional dentures after vestibuloplasty. On average, a greater time investment and more treatment sessions were needed in patients treated with implant-retained overdentures compared to patients treated with conventional dentures. Conclusion: Patients treated with an implant-retained overdenture need more treatment interventions and treatment time than patients treated with conventional dentures.