In this study, seven fiber post materials (Reforpost, D.T. Light-Post, RelyX Fiber Post, Carbopost, Glassix Radiopaque, Dentolic Glass Fiber Post, and Easypost) were evaluated in terms of photon interaction parameters. Fiber post samples were assayed by SEM (Quanta 250 FEG; FEI Ltd., Brno, Czech Republic) and EDS (EDAX Team Software) analysis for basic analysis of material compositions. Using EDAX Team Software, The EDS analysis was performed in areas equal to the center of each fiber post material. Moreover, fiber post materials have been surveyed in terms of photon attenuation characteristics. For this aim, the mass attenuation coefficients (mu/rho) of investigated fiber post materials have been calculated using MCNPX (2.6.0) general-purpose Monte Carlo code. Afterwards, some shielding quantities such as half-value layer (HVL), mean free path (MFP), effective atomic number (Z(eff)) and effective electron density (N-el) have been calculated. The obtained MCNPX results of all fiber post materials have been compared and approved with those of WinXcom program. Also, their gamma ray buildup factors have been determined in a wide energy range of 0.02-20 MeV for penetration depths up to 15 mfp. The results showed that N1 (Carbopost) followed by N2 (Reforpost) sample had superior radiation absorption ability compared to other samples. The outcomes indicate that as the Z(eq) values of the materials increased, the EBF values decreased and the metals (Zr, Ti, Ba), in the samples prevented the buildup of the photons. It was concluded that the percentage of Ba for N1 sample and the increasing percentage of Zr in the other samples increased the radiopacity of samples. It can be concluded that, obtained results can be very useful in diagnostic radiology applications especially in oral diagnosis and dental radiology applications.