Fatigue failure load of immature anterior teeth: influence of different fiber post-core systems

Abstract

The aim was to explore the fracture-behavior, survival and marginal-microgaps within the root-canal of immature anterior teeth restored with different fiber-reinforced post-core composites (FRCs). 180 bovine-incisors were randomly divided into 6 groups (n = 30). One group served as control (group 6). The rest of the teeth were prepared to an internal diameter of 1.6 mm and the apex was sectioned. After application of an MTA-plug, teeth were restored with FRC materials: Group 1: Bioblock technique with short fiber-reinforced composite (SFRC); Group 2: Bioblock technique with flowable SFRC; Group 3: Individually-made FRC post; Group 4: Conventional FRC post; Group 5: dual-cure core build-up composite. After restorations were completed, teeth (n = 5/group) were sectioned and then 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 testing machine in the rest of the specimens. Flowable SFRC application in the root-canal (Group 2) 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 conventional FRC post (Group 4) exhibited a high number of microgaps (38.3%) at the examined interphase in the root-canal. The restoration of immature incisors with the use of flowable SFRC as post-core material displayed promising performance in a matter of fatigue-resistance and survival.

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

“…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 ].…”

Bioblock technique to treat severe internal resorption with subsequent periapical pathology: a case report

“…The operator also had to calculate the thickness of the shallowest layer of SFRC in the canal (4 mm), which left us with an approximately 6-mm-long FRC post for light transfer. As light transfer to the apically placed SFRC is a clinically important part of the Bioblock technique, it has been verified using the microhardness test in previous in vitro studies, which have clearly shown that SFRC can be appropriately cured in the canal with extended light-curing time (80 seconds) [ 15 31 ]. The authors would like to emphasize that in our studies and in this case, the SFRC was placed not more than 6–7 mm deep to the canal orifice, which seems to be a depth at which the setting and curing of SFRC can be controlled.…”

Behavior of the structure of different materials under static force

“…The fracture toughness and flexural strength of new short fiber-reinforced composite materials are similar to that of dentin's, therefore they behave as elastic materials (Lassila et al, 2018). Many studies have shown that better results can be obtained if short fiber-reinforced composite is used rather than conventional composite resin to substitute great amount of missing dentin (Fráter et al, 2019;Fráter et al, 2020;Forster et al, 2016). Furthermore the pattern of fracture is dominantly favorable when using fiber-reinforced composite, meaning the fibers first absorb, then dissipate and redirect the stress in the form of crack and/or fracture towards the surface of the tooth (…”