الفهرس 
ENGLISH ABSTRACTOnly 14 pages are availabe for public view
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Abstract
Glass-ceramic restorations are widely used due to their strength, aesthetics, and ease of fabrication. Heat-pressed restorations offer better strength than other means of fabrication. Efforts to improve strength and microstructure included the addition of ZrO2 with different concentrations and the use of HDM technology. After heat pressing procedures, leftover buttons are usually discarded. However, these leftover buttons are suggested to be repressed with concerns regarding changes in mechanical properties and microstructure.
The effect of repressing on the BFS and microstructure of three different heat-pressed ceramic materials was evaluated in this study. The three heat-pressed ceramics used in this study were IPS e-max®, GC Initial® LiSi Press, and Celtra® Press. New ceramic ingots were used to fabricate pressed specimens while the leftover buttons were used to fabricate repressed specimens. The BFS was evaluated using a piston-on-three-ball test. Additionally, the XRD was used to identify the crystalline phases. Finally, the SEM photomicrographs were used for microstructure analysis.
Repressing had no significant effect on the BFS of both IPS e-max® and GC Initial® LiSi Press. On the other hand, repressing significantly increased the BFS of Celtra® Press. Microstructural analysis by XRD revealed that LS/LD was the main crystalline phase in pressed and repressed groups. The peak positions of XRD patterns after pressing and repressing were similar while peak intensities were different. Additionally, microstructural analysis by SEM photomicrographs (x5000) showed an increase in the grain size after repressing for all specimens.