Stress distribution surrounding endodontic posts.

This study compared the stress distribution during insertion and function of three prefabricated endodontic posts with different designs using the criteria of post length and diameter. Test blocks of photoelastic material were prepared with simulated endodontic canals. Three posts for each design, diameter, and depth were cemented. Each specimen was examined and photographed without load, with 135 Newton (N) compressive force, and with 90 N and/or 135 N oblique force applied at 26 degrees by use of a circular polariscope. Para-Post and Para-Post Plus posts produced similar, evenly distributed patterns of stress using the criteria of diameter, depth, and load. Flexi-Post posts produced asymmetric stress patterns with concentration of stress at each thread. During compressive loading and after cementation alone, Flexi-Post posts displayed significantly higher shoulder stresses and substantially greater stresses along the coronal surface of the post's length than Para-Post and Para-Post Plus posts. Apical stresses were similar for Flexi-Post, Para-Post, and Para-Post Plus posts during compressive loading.