Pilot study comparing the photoelastic stress distribution for four endodontic post systems.

This pilot study compared stress distribution using photoelastic blocks for both vertical loading and oblique loading (26 degrees angle) for four groups of post systems (Flexi-Post, Flexi-Flange, ParaPost and AccessPost dowels). For each group, three test blocks of photoelastic material were prepared with simulated endodontic canals, and the specimens were then photographed. Minimal stresses were observed for all the posts after cementation in the unloaded state. Stress distribution for the Flexi-Post, Flexi-Flange and AccessPost were favourable under vertical loading at 134 N and oblique loadings of 89 N and 134 N. Stress patterns were symmetric over the entire length of these posts. Stress distribution for the ParaPost under vertical loading at 134 N generated stress patterns that were asymmetric with concentration of stresses apically compared to coronally. Stress distribution for the ParaPost during oblique loadings of 89 N and 134 N were asymmetric with stress concentrated apically as compared to coronally. Stress distribution for the Flexi-Post, Flexi-Flange and AccessPost were all favourable under loading conditions studied.