Methods: This research was conducted by experimental method in photo-elastic system. Posts used in this research were two types of Fiber posts called Simple Taper and Double Taper with 0.9 mm diameter and 20 mm length and the applied resin was Epoxy. The research was started by making two photo-elastic models with dental dimensions and installing the mentioned posts in them and the core was made up over each post. Then colorful rings developed by loading each model in Plariscope were photographed.
Results: By loading to 100 N with 90 degree angle the simple taper fiber post had fringe order equal to 1.39 and 2.5 in cervical and apical zones respectively, while these figures were 1.39 and 2.35 for the same conditions and same zones for double taper post. 150 N loading with 30 degree inclination, the simple taper post had fringe order magnitudes in cervical and apical zones equal to 4 and 2.65 respectively while double taper showed 4 and 2.5 fringe order at the similar condition.
Conclusions: In vertical forces, the double taper posts have better stress distribution compared to simple taper ones.