Effect of relining, cement type, and thermocycling on push-out bond strength of fiber reinforced posts

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Statement of the problemImproving the adaptation of fiber reinforced posts through relining may affect the retention of the posts. PurposeTo 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 = 24) received glassix glass fiber posts adapted to the flared canals by relining with composite resin and group (2) (n = 24) received non-relined glassix glass fiber post. Samples of each group were divided into three subgroups (n = 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 = 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. ResultsRelined 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 cement–dentin interface in the relined group, while adhesive failure occurred at the cement-post interface in non-relined group. ConclusionsRelining glass fiber posts with composite resin in order to fit wide flared canals instead of using cement for compensating the discrepancy, improves the push out bond strength of glass fiber posts to root canal dentin. Moreover the use of resin cement with high mechanical properties to lute glass fiber post is highly recommended.