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

S Garoushi; A Ö Akbaşak-Sungur; S Erkut; P K Vallittu; S Uctasli; L Lassila

doi:10.1007/s00784-023-05164-2

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

Clin Oral Investig. 2023 Sep;27(9):5449-5458. doi: 10.1007/s00784-023-05164-2. Epub 2023 Jul 21.

Authors

S Garoushi¹, A Ö Akbaşak-Sungur², S Erkut², P K Vallittu^{3

4}, S Uctasli⁵, L Lassila³

Affiliations

¹ Department of Biomaterials Science and Turku Clinical Biomaterial Center -TCBC, Institute of Dentistry, University of Turku, Turku, Finland. sufgar@utu.fi.
² Department of Prosthetic Dentistry, Faculty of Dentistry, Baskent University, Ankara, Turkey.
³ Department of Biomaterials Science and Turku Clinical Biomaterial Center -TCBC, Institute of Dentistry, University of Turku, Turku, Finland.
⁴ Wellbeing Services County of Southwest Finland, Turku, Finland.
⁵ Department of Prosthodontics, Faculty of Dentistry, University of Ankara, Ankara, Turkey.

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 (F_max) 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.

Keywords: Bilayered restoration; CAD/CAM; Fracture resistance; MOD; Overlays; Short-fiber composite.

MeSH terms

Composite Resins
Dental Caries*
Dental Materials
Dental Stress Analysis
Fractures, Bone*
Humans
Materials Testing
Molar
Tooth, Nonvital*

Substances

Composite Resins
Dental Materials