Retentive characteristics of an internally threaded post system

Internally threaded, stainless steel posts 10 mm in length and 1.82 mm in diameter or stainless-steel Para-Post dowels 1.7 mm in diameter were cemented in extracted human teeth with zinc phosphate cement. Titanium alloy screws 1.5 mm in diameter were placed in the internally threaded posts and tensile force was applied to the screws or Para-Post dowels until dislodgment of the post or fracture. The retention of the Para-Post system was significantly greater than the experimental posts. Although all screws exhibited deformation, there was no breakage or distortion of the internally threaded posts or Para-Post dowels. Retention for both systems exceeded reported forces generated in humans.