الفهرس 
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Abstract
Purpose: The purpose of the present study is to determine the marginal accuracy and internal fit of
endocrown constructed from lithium disilicate ceramics and poly ether ether ketone (PEEK).
Methodology: 16 human lower molars were endodontically treated and prepared to receive endocrown
restorations with Butt joint preparation design. Prepared teeth were equally divided into two groups,
group 1 Lithium disilicate ceramics and group 2 Poly ether ether ketone. All restorations were
CAD/CAM milled using five axis milling machine (CORiTEC 250i Series - imes – icore). Marginal
adaptation was measured by photographs using USB Digital microscope with a built-in camera (Leica
microscope) connected with an IBM compatible personal computer using a fixed magnification of 20X.
Internal fit was measured by replica technique.
Results: Lithium Disilicate endocrowns showed superior results, where they had statistically
significant lower marginal discrepancy (28.86 ±12.69 µm) than PEEK (75.24 ± 28.89 µm) (P-value
=0.002, Effect size =2.349) and statistically significant lower internal discrepancy (122.2±21.7 µm)
than PEEK (163.1±25.1 µm) (P-value =0.043, Effect size =2.042). Regardless of the material of
construction lingual side of endocrown showed the least marginal adaption and internal fit.
Conclusions: Lithium disilicate endocrowns showed better marginal adaption and internal fit than
PEEK endocrowns. Both groups exhibited clinically acceptable marginal discrepancies and fit.
Accordingly, PEEK materials could be used as an alternative to Lithium disilicate for endocrown
construction.
Key words: Lithium disilicate, Poly ether ether ketone, endocrown, marginal adaptation, internal fit.