Purpose: Evaluate the effect of food simulating liquids and thermocycling on miniflexural strength and surface micro-hardness of a resin nano-ceramic material (Lava Ultimate) compared to indirect laboratory composite resin material (Nexco Paste) and direct composite resin material (Filtek Z350 XT).
Material and Methods: A total number of 180 samples were fabricated. The samples were divided equally into 3 groups (n=60). Group 1 (M1) samples were fabricated from the resin nano ceramic CAD/CAM blocks (Lava Ultimate), group 2 (M2) samples were farbricated form indirect micro-hybrid resin composite (Nexco Paste), while group 3 (M3) samples were fabricated from direct resin composite (Filtek Z350 XT). Thirty bars (12X2X2mm) from each material were fabricated to evaluate the mini flexural strength. Thirty disks (8X2mm) were fabricated from each material to evaluate the
surface micro-hardness. The samples of M1 groups were fabricated by cutting from the CAD/CAM block using low speed diamond disk while samples of M2 and M3 samples were fabricated using teflon mold. Each material samples were further subdivided into 6 subgroups; the first subgroup was not immersed into food simulating liquids nor thermocycled,
4 subgroups samples were immersed into food simulating liquids (water, ethanol, heptane and citric acid) and the last subgroup samples were thermocycled. Mini flexural strength test was done using universal testing machine and surface hardness was done using Vickers hardness tester.Results: Lava Ultimate showed the significantly highest mini flexural strength and surface micro-hardness values before and after immersion into food simulating liquids and thermocycling compared to the two other tested materials. Conclusion: According to the results of the present study, Lava Ultimate showed better mini flexural strength and surface micro-hardness compared to the two other
tested materials.