Comparison of stress distribution in two type of metal and non metal posts by photo elastic method

Intrapulpal posts are used as retention for reconstructing of missed crown. Today fiber posts eliminated most of disadvantages of metal posts. The purpose of this study is a comparison of stress distribution in these types of posts (casting and Quartz fiber post) on root canals of teeth with photo elastic method. In this experimental study Quartz fiber and casting posts with length of 15mm and diameter of 0.9mm were used. Four epoxy resin models (10×20×40mm) were made that two of them include casting posts and two other include Quartz fiber posts. Then, cores were prepared for each model. Vertical force of 100N and oblique force with 30' and 150 N were applied on cores and isochromatic fringe patterns around post were recorded in the field of Polariscope. In the vertical loads the minimum cervical stress was observed in casting post that was 1.22 (in Quartz fiber post it was 2.65) But in apical region maximum stress was recorded in casting post that was 1.63(in Quartz fiber post it was 1.38). In the oblique load, casting post showd 1.39 stress in cervical that was the minimum (in Quartz fiber post it was 2.35) and in the apical region, casting post showed the maximum stress that was 1.68 (in Quarts fiber post it was 1) display more critical stress pattern (1.63). In the vertical and oblique loads casting posts shows the maximum stress in the apical region that makes the worse fracture in tooth that couldn’t be prepared but in Quartz fiber post maximum stress was in cervical region so it is more repairable.