الفهرس 
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Abstract
Aim: to assess the difference in tensile bond strength between (PEEK) and lithium
disilicate endocrowns cemented to natural extracted teeth after thermocycling . .
Methodology: 22 recently extracted human maxillary first molar teeth from diabetic
patients ranging from 20 to 50 years old were collected from the Oral and
Maxillofacial Surgical Department of Faculty of Dentistry, Cairo University. All teeth
were subjected to standard endodontic treatment and mounted into resin pattern.
Cavity preparation with butt joint design was made with copious water cooling using
CNC special milling machine . The specimens were divided into 2 equal groups
(n=11). 11 endocrowns were allocated to be constructed from lithium disilicate and
others were allocated to be constructed from PEEK
All endocrowns were cemented on their corresponding teeth using cementation
loading device. All samples were subjected to thermal cycles(6000cycles,5-55c) .
Tensile load was applied using universal testing machine .Retention was measured
by Materials Testing Machine with a loadcell of 5 kN ) Stereomicroscope was
used to investigate the the mode of failure . Data was statistically analyzed used
Kolmogorov-Smirnov and Shapiro-Wilk tests & Student’s t tests (α = 0.05) and failure
mode (%) by the Fisher exact test & chi2 test (p≤0.05).
Results: The mean ± SD values of tensile bond strength were recorded for lithium
disilicate group (2.683±0.56 MPa) meanwhile the mean ± SD value recorded with
PEEK endocrown group(2.119±0.37 MPa) . It was found that lithium disilicate
group recorded statistically significant higher tensile bond strength mean value than
PEEK group.Conclusions: It was found that lithium disilicate endocrown group
recorded statistically significant higher tensile bond stregth mean value than PEEK
endocrown group after thermal loading .