18 Ankylos SynCone conical crowns with 4-degree angle and 18 SynCone conical crowns with 6-degree angle were tested in vitro for a total of 5,000 insertion-separation cycles to investigate their retentive characteristics. Under 20 N insertion force, the retentive force of Ankylos SynCone conical crown system was between 5 and 10 N. The rententive force kept almost constant during the entire testing cycles. It was thus shown that the SynCone conical crown system could potentially provide adequate and constant retentive force to retain implant-supported overdentures. It may be considered to retain implant-supported mandibular overdentures as an alternative to bar attachments.