Fatigue behavior of endodontically treated premolars restored with different fiber-reinforced designs

The aim was to investigate the fatigue survival and marginal-gap inside root-canal of endodontically treated (ET) premolars reinforced by various fiber-reinforced post-core composites (FRCs). Moreover, composite-curing at different depths in canal evaluated. 170 intact upper-premolars were collected randomly divided into ten groups (n = 15). One group served as control (intact-teeth). After endodontic procedure standard MO cavities prepared restored with materials designs. Three-group (A1-A3) either packable flowable short composite (SFRC) core or conventional composite-core. Two-group (B1-B2) SFRCs post (3 mm) core. Four-group (C1-C4) (6 without unidirectional FRC posts (individually-made conventional). completing restorations, teeth from Group C1-C4 5/group) sectioned stained. Specimens viewed under a stereo-microscope percentage microgaps within calculated. Fatigue-survival measured using cyclic-loading machine rest specimens. Application SFRC luting-core material individually-made (Group C3) did not differ intact-teeth regarding fatigue-survival (p > 0.05). produced significantly lower < 0.05) compared intact-teeth. Post/core restorations made C1) had microgap (19.1%) examined interphase than other groups. restoration ET use showed promising achievement fatigue-resistance survival.