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

Abstract

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

Fracture Behavior of Short Fiber-Reinforced Direct Restorations in Large MOD Cavities

“…This is due to the obvious difference in fracture toughness between reinforced and non-reinforced composites. Previous studies have shown that fiber-reinforced composites have the ability to re-direct and stop crack propagation within the materials [ 13 , 17 , 27 ].…”

“…Another major difference between the packable and flowable SFRC is that the flowable one contains 25 wt% of fibers, while in the packable variant this ratio is only 9 wt%. So far, flowable SFRC has yielded promising results when utilized in direct restorations in different clinical situations [ 16 , 17 , 28 ].…”

“…Mechanical testing was carried out in two phases. In the first phase, all restored specimens were submitted to an accelerated fatigue-testing protocol [ 16 , 17 ] by a hydraulic testing machine (Instron ElektroPlus E3000, Norwood, MA, USA) placed parallel to the long axis of the tooth. This phase served the purpose of simulating normal biting forces.…”

“…In 2019, the flowable version of SFRC was introduced with the promise of easy adaptability in both large cavities and limited spaces (such as root canals). So far, flowable SFRC has yielded remarkably favorable results when applied either alone in the root canal (Bioblock technique) [ 16 ] or as a luting material for post luting [ 17 ].…”

Characterization of Experimental Short-Fiber-Reinforced Dual-Cure Core Build-Up Resin Composites

“…This approach, also called the individual fiber post concept, has been used successfully with continuous long glass fibers [ 23 , 24 ]. On the other hand, fiber-reinforced core composites showed the ability to re-direct and stop crack propagation within the materials [ 25 ]. The presence of such energy-absorbing and stress-distributing fibers allows crack propagation to be deflected away from the bulk of the material and toward the peripheries [ 22 , 26 , 27 ].…”