THE EFFECT OF REPEATED HEAT-PRESSING ON THE BIAXIAL FLEXURAL STRENGTH AND SURFACE ROUGHNESS OF LITHIUM DISLILICATE GLASS-CERAMICS
EL-Etreby, Amr S.
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Statement of problem: During heat-pressing of lithium dislilicate glass-ceramics, It is more economical to press several restorations from one ingot at the same time. However, this is often not possible and may result in a considerable amount of leftover material. It has been reported that the leftover materials after heat-pressing are reused in some dental laboratories. Sufficient knowledge about the consequences of such procedure is not available. The issue is thereby raised whether the leftover material should be discarded or reused. Purpose: The aim of the present study was to evaluate the effect of repeated heat-pressing on biaxial flexural strength and surface roughness of lithium dislilicate pressable glass-ceramics (IPS e.max Press). As well as to describe the microstructural features present in fresh-pressed, and repressed material using Xray diffraction, EDAX and SEM Materials and methods: Twenty pressed and repressed samples were prepared following the manufacturers’ recommendations measuring 15 mm × 1 mm per material. Biaxial flexure (piston on 3-ball method) was used to assess strength. X-ray diffraction was performed to identify the crystalline phases, and a scanning electron microscope was used to disclose microstructural features. Also surface roughness was evaluated
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