EFFECTS OF THERMAL AGEING ON THE MECHANICAL PROPERTIES OF CAD-CAM CERAMIC MATERIALS

This study aimed to evaluate the effect of thermal ageing on the Vickers microhardness, fracture toughness and surface microstructures of four CAD-CAM dental ceramic materials.Specimens of a polymer-infiltrated ceramic network (PICN) (ENA; Vita Enamic), a resin nano-ceramic (CERA; GC Cerasmart), a zirconia-reinforced lithium silicate (ZLS) ceramic (DUO; Celtra Duo), and polycrystalline zirconia (ZIR; IPS e.max ZirCAD) were prepared (n = 10).Each test was subjected to a thermocycling process (5 to 55 C, 20 s, 10,000 cycles).The Vickers microhardness and fracture toughness were measured and re-evaluated after the thermal ageing.Surface microstructures were observed by scanning electron microscopy.Statistical analyses were performed using the paired sample t-test and the Wilcoxon test ( = 0.05).ENA and CERA exhibited a decrease in the microhardness after ageing.The microhardness change of ENA was more significant than DUO.ENA, DUO and ZIR showed a decrease in the fracture toughness.The change in the fracture toughness of ZIR was more significant than ENA, CERA, and DUO.ENA and CERA did not exhibit a stable image on the microscopic evaluation.The microhardness and fracture toughness of the CAD-CAM ceramics were influenced by ageing.Clinicians should consider how well the materials they use can adapt to the oral environment and choose the material accordingly.