Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Dental Materials

Aim: Investigate aging effect of three ceramic CAD/CAM block materials: lithium disilicate(LD), translucent zirconia(TZ) and zirconia reinforced lithium silicate(ZLD) on their hydrolytic resistance, microstructure, flexure strength and translucency. Material and methods: Fourteen disc shaped specimens were prepared from each material(12mm diameter and 1.2 mm thickness). Seven specimens per material were subjected to accelerated aging according to ISO standard:6872 which specifies boiling in 4% acetic acid at 800C for 16 hours. While the other seven were considered as control. Weight loss was measured by weighing specimens before and after aging. Crystalline structure was investigated before and after aging by x-ray diffraction(XRD) while microstructure by scanning electron microscope(SEM). All specimens were subjected to translucency parameter testing using spectrophotometry then biaxial flexure strength testing. Statistical analysis performed with IBM®SPSS®Statistics, Windows Version20. Results: No significant percentage loss of weight after aging of the three materials. LD had the highest translucency followed by ZLD and TZ was the least. In addition, LD translucency decreased by aging while translucency of the others was not affected. TZ had the highest flexure strength while there was no difference between the others. Flexure strength of the three materials was not affected by aging and XRD graphs showed no change after aging of the three materials

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