Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

Aim of the present study was to evaluate the efficacy of post length and post material on the pull-out bond strength of individually formable glass fiber post versus custom made metal post on endodontically treated mandibular premolar teeth. Sixty six extracted human mandibular premolars teeth were endodontically treated, they decoronated 2 mm above the cementoenamel junction and randomly divided into two main groups (Group A and B) based on the post materials to be used. Group A: individually formed glass FRC posts (ever stick post), Group B: custom made metal post (Ni - Cr). Moreover, samples of each group were divided into 3 subgroups (subgroup 1, 2, 3) (n = 22) according to the post length: subgroup I : 14.0mm; subgroup II: 12.0 mm; subgroup III: 10.0 mm. All of the posts were luted with dual - polymerizing self-adhesive universal resin cement (relyX unicem). The samples were subjected to a pull-out bond strength test in a universal testing machine at a crosshead speed of 0.5 mm/min. The results, in newtons, were analyzed with two-way ANOVA and the pair wise Tukey post hoc test (Ü = .05). Two samples from each group were processed for digital microscope observations in order to investigate the mode of failure at the post/cement interface. Two - way ANOVA showed statistically non - significant difference (P > 0.05) between cast metal post group (227.77 ± 42.40 N) and everStick post group (225.15 ± 23.65N). Moreover, post length with 14mm recorded the highest statistically significant difference (p < 0.05) mean value (278.45 ± 33.81 N) followed by post length 12mm (241.37 ± 42.74 N) then post length 10mm recorded the lowest statistically significant difference (p < 0.05) mean value 159.57 ± 17.53 N). It can be concluded that the pull out bond strength (debonding force is directly proportional to post length

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