The purpose of this study is to compare mainly mucosa-supported and combined mucosa-implant-supported complete mandibular overdentures. Ten completely edentulous patients received 20 press-fit dental implants at the canine regions of the mandible. Each patient received 2 implants, which were left submerged and unloaded for 4 months. The patients were divided into 2 groups: group I patients received mandibular overdentures retained by a magnet attachment (mainly mucosa-supported overdenture). Group II patients received mandibular overdentures retained by a bar attachment (combined mucosa-implant-supported overdenture). The patients were evaluated clinically and radiographically immediately after overdenture delivery and after 6 months, 12 months, and 18 months. The results showed that the mainly mucosa-supported overdentures had less bone resorption distal to the implant in comparison to the combined mucosa-implant-supported overdentures. Plaque index score was significantly high in the group treated with magnet-retained overdentures. After 18 months follow up, the group treated with combined mucosa-implant-supported overdentures showed a significant increase in gingival inflammation when compared with the other group. The type of attachment or support may affect gingival inflammation or plaque accumulation. Increased functional load may affect bone density and resorption.