Influence of short-fiber composite base on fracture behavior of direct and indirect restorations

Abstract

Objectives The aim was to examine the influence of short-fiber composite (SFC) core on the fracture-behavior of different types of indirect posterior restorations. In addition, the effect of thickness ratio of SFC-core to the thickness of the veneering conventional composite (PFC) on fracture-behavior of bi-structured composite restorations was evaluated. Materials and methods MOD cavities with removed palatal cusps were prepared on 90 intact molars. Five groups of direct overlay restorations (n = 10/group) were fabricated having a SFC-core (everX Flow) with various thicknesses (0, 1, 2, 3, 4 mm) and layer of surface PFC (G-aenial Anterior), remaining the thickness of the bi-structure restoration to be 5 mm. Four groups of CAD/CAM-made restorations (Cerasmart 270 and e-max CAD) were fabricated either with 2-mm layer of SFC-core or without fiber reinforcement. Intact teeth (n = 10) were used as control group. Restorations were statically loaded until fracture. Fracture patterns were evaluated visually. Data were analyzed using ANOVA (p = 0.05). Results With indirect overlay restorations, no statistically significant differences (p > 0.05) were observed in the load-bearing capacities between restorations reinforced by 2-mm SFC-core (bi-structured) and those fabricated from plain restorative materials. ANOVA displayed that direct overlay restorations made from 4-mm layer thickness of SFC-core had significantly higher load-bearing capacities (3050 ± 574 N) (p < 0.05) among all the groups tested. Conclusions Restorations (direct/indirect) combining SFC-core and a surface layer of conventional material demonstrated encouraging achievement in reference to fracture behavior. Clinical relevance The use of flowable short-fiber composite as reinforcing base with large direct and indirect restorations may result in more repairable failure.

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

“…Our results show the superiority of bi-structured direct restorations over conventional composite fillings when tested with extremely high forces. This is in line with other studies [ 26 , 28 ]. Our results also suggest that the consistency (highly filled flowable or conventional packable) of the occlusally placed composite is not a significant factor in the fracture resistance of a direct restoration utilizing flowable SFRC.…”

“…In the static load-to-fracture test, all bi-structured restorations (SFRC + conventional composite coverage), irrespective of the application mode of flowable SFRC or the consistency of the occlusal composite material, showed significantly higher fracture toughness in comparison to the control group (conventional composite filling). This is in accordance with the findings of Garoushi et al, where flowable SFRC covered with a minimal amount of composite showed significantly higher fracture resistance compared to conventional composite filling [28]. However, in that study the cavities were larger than those seen in this study.…”

“…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 ].…”

Fatigue performance of endodontically treated premolars restored with direct and indirect cuspal coverage restorations utilizing fiber-reinforced cores

“…Short fiber-reinforced core composites, on the other hand, showed the ability to re-direct and stop crack propagation within the materials [31]. The presence of such energyabsorbing and stress-distributing fibers allows crack propagation to be deflected away from the bulk of the material and toward the peripheries [62][63][64].…”

“…Therefore, the second null hypothesis was accepted. It is clearly shown in the literature that the brittleness of the conventional PFC materials generates bulk fracture propagating easily through the whole thickness of the restoration, reaching the tooth substance to be propagated further [62,63]. Thus, the basic characteristics of the PFC materials do not offer significant protection against fatigue crack propagation.…”