Objectives: Retention of mandibular complete dentures on two or four interforaminal implants is considered the most reliable procedure in implant therapy. There are different retention elements available for all implant systems. The aim of the present study was to clinically evaluate patients with a mandibular overdenture supported by the Ankylos SynCone system (Dentsply). Method and Materials: Thirty-nine patients were treated with 156 implants. The treatment method was based on immediate loading of four interforaminal implants without the use of a bar retainer. The denture was placed on and retained by prefabricated conical crowns that were inserted into the existing denture base by direct intraoral polymerization immediately after surgery and supported by the corresponding conical primary implant abutments. Results: The cumulative implant survival rate was 98.7% (two failures), while the prosthesis survival rate was 100%. After a total observation of 30.3 months (range 12 to 60 months), all other implants presented healthy peri-implant soft tissue conditions showing low value of clinical parameters. Conclusion: This method facilitates secondary splinting of the inserted complete denture. The conical crowns concept presented here resulted in stable complete denture retention, reduced the denture base, and improved oral hygiene. Keywords: complete dentures, dental implants, edentulous mandible, immediate loading, overdentures, prefabricated telescopic restorations