Evaluation of the physical properties and bond strength of short fiber-reinforced resin composites

Objectives: To assess physical properties of the newly developed fiber-reinforced flowable composite everX Flow™ (eXF) and the packable composite everX Posterior™ (eXP), compared to the particulate-filler flowable composite Filtek™ Bulk Fill Flowable Restorative (FBFf) and the packable resin composite Filtek™ One Bulk Fill Restorative (FBF). Methods: Surface roughness, flexural strength, and microtensile bond strength tests were performed (n=10). After the microtensile tests, fracture type was identified with both a stereomicroscope and a scanning electron microscope. The data were statistically analyzed with one-way ANOVA followed by Tukey's post-hoc tests. Results: Statistically significant (p<0.05) differences were found between surface roughness of eXP and both FBF and FBFf, but no other significant (p≥0.05) differences were observed (eXP, 0.78±0.22 μm; eXF, 0.61±0.08 μm; FBF, 0.47±0.18 μm; FBFf, 0.42±0.11 μm). The flexural strength values were: 126.69±14.65 MPa for eXF; 114.08±9.34 MPa for eXP; 94.70±7.06 MPa for FBF; 83.37±7.44 MPa for FBFf. Statistically significant differences were noted between eXF and eXP (p<0.05). For the microtensile bond strength, the results were: 34.37±9.25 MPa for eXF; 28.68±6.50 MPa for eXP; 24.90±4.52 MPa for FBF; 21.10±3.95 MPa for FBFf. eXP showed statistically significant differences (p<0.05) when compared to FBFf, while eXF showed significant (p<0.05) differences compared to both FBF and FBFf. Conclusions: The results indicated that eXF and eXP are suitable for posterior restorations in terms of flexural strength and microtensile bond strength. However, due to their higher surface roughness, it is suggested that these composites may not be appropriate for use as final restorations.