Purpose: The purpose was to assess and compare self-reported oral health and oral and general health related quality of life (OHRQoL and HRQoL) in two groups of edentulous adults who reported dissatisfaction with their mandibular dentures, and who were treated with a conventional relining of this denture or by having it converted into an implant-retained one. Materials and Methods: Sixty subjects were randomly allocated into two equal groups, a relined conventional denture (RCD) group and an implant-retained overdenture (IOD) group. Data on demographics, oral health, OHRQoL, and HRQoL were recorded by means of a self-administered questionnaire at baseline, 3 months, and 2 years. Results: Fifty-four subjects completed the protocol, 28 in the IOD-group and 26 in the RCD-group. The IOD group reported significant improvement in oral health and Oral Health Impact Profile (OHIP-20) sum score and all its domains after 3 months. The improvements remained stable at the 2-year control. The RCD group reported almost no significant improvements. Neither group reported improved HRQoL. Conclusion: The results of this study support the findings from other RCT studies that to implant-retain the mandibular denture significantly improves self-reported oral health and OHRQoL. This treatment modality should be a minimum standard of care in complete denture wearers dissatisfied with their mandibular denture.