Fig. 1

Schematic diagram showing the flow of specimens’ preparation and the tests employed. One hundred bard from each CAD-CAM material type were sectioned. Zirconia and lithium disilicate bars underwent sintering and crystallisation firing cycles, respectively, while nanohybrid resin composite and polymer-infiltrated glass network ceramic did not receive any firing treatment. All bars were embedded in 4 erosive media and artificial saliva for 24 h at 37℃. Half of the bars were then tested for microhardness and the other was tested for fracture toughness through quantitative fractographic method