الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Dowels would be suggested when there are insufficient tooth tissues. An alternate treatment option for conditions requiring a high level of aesthetic performance is tooth-colored post-and-core systems. An alternative material for the construction of attractive posts might be PEEK. The polyaryletherketones family of ultra-high performance thermoplastic polymers includes both polyetherketoneketone (PEKK) and polyetheretherketone (PEEK) (PAEKs). Lithium discilicate glass ceramics was the material of choice of this study due to their chemical resistance, aesthetic appeal, and improved translucency. This sudy was conducted to test the esthetical possibility of color modification of Lithium disilicate glass ceramic crown when used different types of post and core as casted metal post and casted tooth coloured PEEK post and core using spectrophotometric analysis. Thirty recently extracted human maxillary central incisors were included in this study . The crown of the selected teeth was sectioned perpendicular to the long axis from 1.5 to 2 mm coronal to the cementoenamel junction and the root canals were endodontically treated and obturated, then the gutta bercha was mechanically removed to provide post space . A duralay impression of the canals was taken .The samples was devided in to three groups : group 1 (casted Ni Cr post and core ) ,group 2( casted white PEEK post and core )and group 3 ( casted Ivory PEKK post and core) . Lithium discilicate crowns with 1mm thickness were fabricated using press technique then cemented by transparent self adhesive resin cement over three groups of post and core. The color of the Emax crown was examined with the spectophotometer and recorded to be compared with different groups to determine the effect of dowel color on the Emax crown . In the current study we evaluated the color change of lithium discilicate crowns when using three different groups of post and core : group 1 NiCr post and core , group 2 PEEK post and core and group 3 PEKK post and core using spectrophometeric analysis .The numerical data was represented by means ,standard deviation (SD) , Range and P- value which was set the significant level at (P≤ 0.001). The statistical analysis was performed using one way ANOVA test with IBS SPSS Version 20 for Windows . Color measurement ΔE (color change ) of group I (Ni Cr post and core) showed the highest value (14.007) when compared to group II (PEEK post and core) with ΔE value (13.303) and group III (PEKK post and core) with ΔE value (11.831) .There was no significant difference in ΔE color measurement between three variables with ( P-value=0.115).