الفهرس 
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Abstract
Aim: The purpose of this study is to evaluate the retention of PEEK-based posterior crowns after different surface treatment protocols (sandblasting using 110 micron alumina particles, acid etching using sulphuric acid and combined sandblasting and acid etching).
Methodology: 24 extracted human natural molars that were mounted in epoxy blocks and they were prepared to receive PEEK copings that were divided into 3 groups. The first group was treated with sandblasting with 110 micron alumina particles under 2 bar, The second group was treated with 98% sulphuric acid for 60 seconds then rinsed with running water for 60 seconds, The third group was treated with sandblasting and acid etching together then all copings were cemented to their corresponding teeth with Relyx Ultimate clicker then after cementation all copings were subjected to a pull out test using a Universal testing machine . After the mesurments the teeth were examined under digital microscope to detect the mode of failure.
Results: For Sandblasted group the mean ± SD values were (80.66± 5.54N) with minimum value (59.31 N) and maximum value (108.27 N), while for Acid etched group the mean ± SD values were (87.45± 5.56 N) with minimum value (81.96 N) and maximum value (101.34 N). Meanwhile the mean ± SD values for Sandblasted and Acid etched group together were (92.43± 5.51 N) with minimum value (79.67 N) and maximum value (106.19 N).
In accordance to the mode of failure In SB and AE treated group, the failure mode pattern was predominantly adhesive while minority was mixed.
In SB + AE treated group samples showed equal % between adhesive and mixed failure mode patterns. There was no record for cohesive failure mode pattern in all groups.
Conclusions: Within the limitation of this study; The surface treatment that was preformed by using sandblasting and sulphuric acid etching togethere showed the highest results in accordance to retention of the copings.The use of different surface treatment protocols gives a reliable results in accordance to retention