Evaluation of Fracture-behavior in Short Fiber-reinforced Direct and Indirect Overlay Restorations

Abstract

<p>Objectives<br>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.</p><p>Materials and methods<br>A total of 120 molars were used to create MOD cavities, with palatal cusps removed. Four different groups of direct overlays were then made (<em>n </em>= 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.<br></p><p>Results<br>There were no statistically significant differences (<em>p</em> > 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) (<em>p</em> < 0.05) when compared to all other groups tested, according to the statistical analysis ANOVA.<br></p><p>Conclusions<br>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.</p><p>Clinical relevance<br>The use of SFC as bulk reinforcing base will significantly improve the loading performance of directly layered restorations.<br></p>