Purpose: This randomized clinical trial tested hypotheses that there are no differences in patient satisfaction, component costs, or treatment and maintenance times when mandibular overdentures are retained by one or two implants. Materials and Methods: Subjects wearing conventional complete dentures were randomized to receive either one midline or two bilateral mandibular implants followed by a mandibular denture reline to incorporate implant retention. They indicated on a visual analog scale satisfaction with their dentures before implants and at 2 months and 1 year after implant retention. Satisfaction outcomes between the two groups were compared using the Wilcoxon/Mann-Whitney nonparametric rank test, while changes within each group were analyzed using signed-rank tests. Component costs and times for surgery, prosthodontic treatment, and maintenance were compared using nonparametric and t tests. Results: Eighty-six subjects enrolled in this study and 85 completed the 1-year follow-up, at which median satisfaction was 93 (maximum 100) in the single-implant group and 94 in the two-implant group (P > .5). Within each group, median improvement in satisfaction was similarly dramatic (~44) and significant (P .001). Prosthodontic maintenance time was similar for both groups (P > .37), but the singleimplant group had significantly lower component costs (P .001) and lower times for surgery (P = .002), postsurgical denture maintenance (P = .021), and denture reline (P .001). Five implants failed in four subjects, all in the two-implant group and all before denture reline. Conclusion: Lower component costs and treatment times, with comparable satisfaction and maintenance time over the first year, indicate that a mandibular overdenture retained by a single midline implant may be an alternative to the customary two-implant overdenture for maladaptive denture patients.