Statement of the problem: Improving the adaptation of fiber reinforced posts through relining may affect the retention of the posts. Purpose: To investigate the effect of post relining, cement type, and thermocycling on the push-out bond strength of fiber reinforced posts. Materials and methods: (48) endodontically treated human teeth were excessively flared using diamond stones. The teeth were divided into two groups; group (1) (n ¼ 24) received glassix glass fiber posts adapted to the flared canals by relining with composite resin and group (2) (n ¼ 24) received non-relined glassix glass fiber post. Samples of each group were divided into three subgroups (n ¼ 8) according to the type of cement used; subgroup (a): luted using Metacem Refill, a total etch resin cement, subgroup (b): luted using Rely X Unicem, a self-adhesive resin cement and subgroup (c): luted using RelyX Luting, a resin modified glass ionomer cement. Half the samples of each subgroup (n ¼ 4) were subjected to thermocycling. The samples were sectioned horizontally into 2 mm thick slices yielding 3 sections for each sample. Retention was evaluated using push out bond strength test using universal testing machine. The maximum failure load was recorded and used to calculate the push-out bond strength. Data was statistically analyzed and mode of failure was assessed using magnifying glass. Results: Relined posts showed statistically significantly higher mean push-out bond strength than non-relined posts. Rely X Unicem showed the statistically significantly highest mean push-out bond strength among tested cements. Metacem showed significantly lower mean push-out bond strength than Rely X Unicem. Rely X Luting showed the statistically significantly lowest mean push-out bond strengths. There was no statistically significant difference between mean push-out bond strength with and without thermocycling. Most failures occurred at the cementedentin interface in the relined group, while adhesive failure occurred at the cement-post interface in non-relined group
