Evaluation of fracture behavior in short fiber–reinforced direct and indirect overlay restorations

Abstract

Objectives The aim was to assess how incorporating a short-fiber composite (SFC) core would affect the fracture behavior of direct and indirect overlays. Furthermore, to examine the relationship between the thickness ratio of SFC core to particulate-filled composite (PFC) veneering and the fracture-behavior of bilayered-structured restorations. Materials and methods A total of 120 molars were used to create MOD cavities, with palatal cusps removed. Four different groups of direct overlays were then made (n = 15/group), all of which featured a SFC core (everX Flow) with varying thicknesses (0, 1, 4, and 5 mm), as well as a surface layer of PFC (G-aenial Posterior), with the overall thickness of the bilayered-structured restoration set at 5 mm. Additionally, four groups of CAD/CAM restorations were created (Cerasmart 270 and Initial LiSi Block), with or without 2 mm of SFC core reinforcement. Following the fabrication of these restorations, cyclic fatigue aging was carried out for a total of 500,000 cycles, with an applied maximum load (Fmax) of 150 N. Subsequently, each restoration underwent quasi-static loading until fracture. The fracture mode was subsequently evaluated using optical microscopy and SEM. Results There were no statistically significant differences (p > 0.05) observed in the fracture resistance of indirect overlays reinforced with a 2-mm SFC core compared to those made solely from restorative materials. Direct overlays constructed using plain SFC or with a 4-mm layer thickness of SFC core exhibited significantly higher fracture resistance values (2674 ± 465 and 2537 ± 561 N) (p < 0.05) when compared to all other groups tested, according to the statistical analysis ANOVA. Conclusions The most effective method for restoring large MOD cavities was found to be direct restoration using SFC either alone or as a bulk core in combination with PFC composite. Clinical relevance The use of SFC as bulk reinforcing base will significantly improve the loading performance of directly layered restorations.

Mechanical Performance of Extensive Restorations Made with Short Fiber-Reinforced Composites without Coverage: A Systematic Review of In Vitro Studies

“…In accordance with our inclusion criteria, all the selected studies tested restorations solely made with an SFRC material and included a comparison group made with conventional PFC. Ten of the selected studies used an SFRC with a paste consistency (experimental fiber composite, EverX Posterior) [ 23 , 24 , 25 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ], six of them used a flowable SFRC [ 26 , 27 , 28 , 36 , 37 , 38 ], and four of them made restorations using a short-fiber-reinforced CAD-CAM composite material [ 30 , 32 , 36 , 37 ]. All the included studies reported significantly higher load-bearing capacities for the groups restored solely with SFRCs compared to the PFC control groups.…”

“…Furthermore, in those articles where a material analysis was performed, in all cases, significantly higher fracture toughness was measured in the SFRC groups. Fifteen of the included studies examined the fracture pattern in the failed specimens [ 23 , 24 , 25 , 26 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 38 ]. In thirteen cases, a more favorable fracture pattern was reported for the SFRC groups compared to their controls.…”

“…The details of the methodological quality of the publications are shown in Table 3 . Thirteen of the publications had medium risk of bias, while three of the studies had low risk [ 24 , 26 , 38 ].…”

“…In clinical situations, the load-bearing capacity is highly dependent on the quantity and quality of the remaining tooth structure. Four of the included studies used extracted human teeth for these tests [ 23 , 24 , 25 , 26 ]. While these in vitro investigations have a high clinical relevance, the usage of human teeth adds another variable to this equation in terms of mechanical parameters and survival of the restoration–tooth unit.…”

“…Apart from this study, all the other articles reported a significantly higher fracture resistance for the SFRC group compared to the PFC control group. Eight of the included studies compared an uncovered, plain SFRC group to a bi-layered SFRC + PFC group as well [ 25 , 26 , 28 , 31 , 34 , 35 , 38 ]. In all eight publications, the uncovered SFRC performed better than the bi-layered group.…”