This study was conducted to test the sealing ability of high temperature thermoplasticized gutta percha and evaluate the effect of temperature and gutta percha on sealer permeability to determine sealer penetration into dentinal tubules and apical seal. Ninety extracted human single rooted teeth with straight canals were selected and prepared in a crown down manner utilizing the ProTaper Universal Ni-Ti rotary system. Apical preparation was finished at F3. The irrigation protocol included flushes of 5.25% NaOCl after each file. Smear layer was removed by alternative flushes of 17% EDTA then 5.25% NaOCl. A final rinse of the canal with 17% EDTA and distilled water was done. The 90 teeth were divided into three main groups A, B, and C according to obturation technique used lateral condensation, thermoplastic injectable, or warm vertical condensation (n=26), and a control group (n=12). Each group was further subdivided into 2 groups according to evaluation methods and the control group subdivided into positive and negative control groups.