[The stress transmission of prefabricated root canal posts]

Photoelastic stress analyses were done with nine prefabricated endodontic posts under axial and diagonal (26 degrees) burden with 5, 10, 15, 20, 25 kg. Stress presented itself in form of interference fringes, which became visible under polarized light. The tapered, grooved pins (Mooser and Unimetric) caused fringes along the shaft and apical as well. They worked at higher stress like a wedge. Cylindrical pins (Para Post Unity 5, Radix-anchor) showed relative strong fringes predominantly at the top. Cylindrically tapered pins (Tenax, CM, Pivomatic) and a conical pin with flat thread and grooves (Exatec-S) caused a more favourable stress distribution and the fringes at the top were clearly slighter.