الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 111 |  |  |
| | | from | 111 | | |
Abstract
This study was designed to evaluate the effect of the multiple firings on color, translucency and biaxial flexure strength of pressable and machinable lithium disilicate ceramic.
The most common technique to build a restoration is to form a core then cut back the incisal area to create mamelons and characteristics by the application of various incisal porcelains then fired to attain a full contoured restoration. To produce a natural appearance with correct form and color the all ceramic restoration is fired several times. There it is crucial evaluate the effect of these firings on the restoration
Twenty-one specimens were prepared into discs of 10mm diameter and 1mm thickness of Rosetta SP and Rosetta SM each were tested for color stability, translucency and biaxial flexural strength after 1st,3rd and 5th firings.
The color and translucency were tested using an in-lab spectrophotometer then color stability and translucency parameter were calculated. Biaxial flexure strength was measured with a universal testing machine using piston on three ball test.
The results revealed that there is statistical significance in the translucency due to the firing cycles, but Rosetta SM showed significantly higher translucency than Rosetta SP. This difference in the types of ceramics maybe due to the smaller crystal size of the Rosetta SM, which lead to a more translucent restoration.
The color change (ΔE) was significant between the firing cycles especially between the 1st and 5th firing cycle. Also, Rosetta SM color change (ΔE) was higher than Rosetta SP. The cause of the color change is due to the instability of the metal oxide during repeated firings.
The Biaxial flexural strength of the Rosetta SM was significantly higher than Rosetta SP which may be due to the larger crystal sizes of the of the Rosetta SP which leads to residual stresses which counteract the interlocking effect of long crystals.