The serrated parallel post provides the greatest retention due to its increased surface area and mechanical interlocking within the root canal. Unlike tapered posts, parallel posts maintain uniform thickness, preventing stress concentration and maximizing frictional resistance. The serrations further enhance retention by creating micro-retentions without excessive dentin removal. This combination optimizes post stability and minimizes risk of post dislodgement in endodontically treated teeth.

Reference: Stewart’s Clinical Removable Partial Prosthodontics, Stewart, 4th Edition.