Effect of fiber-reinforced composites on the fracture strength values under different thickness of CAD/CAM systems

To evaluate the effect of fiber-reinforced composites on fracture-strength (FS) values of nanoceramic CAD/CAM restoration materials with different thicknesses.

One-hundred extracted, caries-free human maxillary premolars were divided into two main groups based on the thickness of the nanoceramic CAD/CAM restorative material (2 mm and 3 mm). Within each main group, five subgroups were formed: one control, one non-fiber (G-ænial Universal Flo), and three fiber-reinforced experimental subgroups (Ribbond, EverStick NET, and EverX Flow). Standardized MOD cavities were prepared in all experimental groups, extending 2 mm below the cementoenamel junction and 3 mm wide on the proximal walls. All restorations were fabricated using Cerasmart blocks and cemented with G-CEM Link Force dual-cure resin cement. FS testing was performed, and the data were statistically analysed (p < 0.05).

Ribbond significantly increased fracture resistance compared to the control group (p = 0.047), while other fiber materials showed no significant difference (p > 0.05). An increase in restorative material thickness enhanced fracture resistance in fiber-reinforced groups (p < 0.001). In the control group, variation in the remaining tooth structure height did not significantly affect fracture resistance (p = 0.078). There was also no significant difference in the interaction between the fiber-reinforced composite type and restoration thickness (p>0.05).

Although the thickness of the restorative material may influence FS, the use of fiber-reinforced composites does not appear to significantly affect the fracture resistance of nanoceramic CAD/CAM restorations.