Shear Bond Strength and Failure Mode of a Novel Experimental Short Fiber-Reinforced CAD/CAM Block Material (In Vitro Study)

CAD/CAM block, Resin-based composite, Short-fiber-reinforced composite, Shear-bond strength test, bond strength.

Zakaria Jamal Mohammad1
B.D.S., M.Sc.. College of Dentistry, Hawler
Medical University, Erbil 44001, Iraq . Email:
zakarya.mohammed@den.hmu.edu.krd

Dr. Diyar Khalid Bakir2
B.D.S., M.Sc., Ph.D. College of Dentistry,
Hawler Medical University, Erbil 44001, Iraq.
Email: diyar.bakr@hmu.edu.krd.

Address for correspondence: Zakaria Jamal
Mohammad. B.D.S., M.Sc.. College of
Dentistry, Hawler Medical University, Erbil
44001, Iraq . Email:
zakarya.mohammed@den.hmu.edu.krd

Received:29-06-2026
Revised:02-08-2026
Accepted:08-08-2026

European Journal of Prosthodontics and Restorative Dentistry (2026) 34 (7s), 859–869

Shear Bond Strength and Failure Mode of a Novel Experimental Short Fiber Reinforced CAD/CAM Block Material (In Vitro Study)

Although short fiber-reinforced composites demonstrate favorable mechanical properties, their bonding performance as CAD/CAM materials is not well documented specifically for indirect restoration. This study compared the shear bond strength of a novel experimental SFRC CAD/CAM block with conventional resin-based CAD/CAM materials with different microstructures. Field-emission scanning electron microscopy (FESEM) was used to examine the microstructural features of specimens from each group. For shear bond strength testing, specimens were allocated into three groups: Group 1 (Grandio Blocs), Group 2 (Cerasmart 270), and Group 3 (experimental SFRC CAD/CAM block), with 15 specimens in each group. After surface treatment by air abrasion with aluminum oxide (50 µm particles at 2 bar pressure), the primer was applied, and a dual-cured self-adhesive resin cement was used to bond all specimens. Subsequently, a universal testing machine equipped with a 5 kN load cell was used to debond the specimens. A FESEM analysis revealed that the experimental SFRC CAD/CAM block consisted of a polymeric resin matrix reinforced with randomly oriented and uniformly dispersed short fibers. In contrast, Grandio Blocs exhibited a densely packed nanohybrid microstructure characterized by irregularly shaped inorganic fillers. Cerasmart 270 demonstrated a more homogeneous microstructure, with evenly distributed nanosized spherical fillers within the resin matrix. The Experimental SFRC showed the highest bond strength (17.279 ± 0.711 MPa), surpassing the Grandio blocs (12.607 ± 0.781 MPa) and Cerasmart 270 groups (12.703 ± 0.593 MPA) (p < 0.001) and highlighting its superior resistance to debonding. The Grandio blocs and Cerasmart 270 groups were not statistically different from each other (p = 1.000). The presence and distribution of reinforcing fibers in the experimental block likely account for its higher shear bond strength compared with other groups that provide more microretentive sites for silane coupling.

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