Methods: 3 disc-specimens were prepared (12mm x 2.5mm) of each of the following materials: X-tra base, Venus Bulk Fill, SureFil SDR, (bulk-fill composites), and GrandioSO, Venus Diamond and Spectrum TPH3 (conventional resin-composites). Specimens for each material were incubated for 24 hrs at 37 °C before testing. All specimens were tested at an edge distance of ) 0.5 mm using an edge strength measurement device (CK10, N Engineering Systems, Nottingham, UK) with a diamond Vickers indenter and the force-to-fracture was recorded. Failure modes were examined under the integral CK10microscope. One-way ANOVA and Tukey post-hoc tests were used to detect statistical differences (P<0.01) in edge strength among the materials.
Results: The force (N)-to-fracture at a distance of 0.5 mm from the edge was defined as the Edge Strength. Mean (SD) values of edge strength (N) ranged from 114.0 (7.1) for SDR to 157.8 (6.4) for GrandioSO. These values were significantly different (P<0.01). There was no difference between bulk-fill composites. Chipping was the predominant mode of failure for all materials.
Conclusions: GrandioSO showed the highest edge strength. Bulk-fill composites had comparable edge strength with conventional resin-composites.