Purpose. to compare the stress distribution induced by PEEK versus zirconium employed in extra coronal attachment of partial denture in kennedy class II.
Material and methods.
A virtual mandibular kennedy class II model was designed having canine and first premolar teeth as terminal abutments. Two strain gauge slots were designed on the software to receive the strain gauge rosettes. The first one was placed 1mm distal to the socket of the first premolar and the second slot 1 cm distance away from the first one. Two models were 3D printed. The attachment design was selected from software library. Crowns and attachment were milled out of PEEK and zirconia materials in the first and second models respectively. Five RPDs were constructed for each model. Bilateral load of 100N was applied. For each removable partial denture, five measurements were made. The data obtained were statistically analyzed by using unpaired t test to study the difference between group mean values (p< 0.01).

Results.
Unpaired t test showed statistical significance between both materials in both slots during bilateral loading. The microstrain values recorded distal to the loaded abutment were less for PEEK compared to zirconia .The microstrain values recorded on the residual ridge were higher for PEEK compared to zirconia.

Conclusions. Within the limitations of this study, it was concluded that the use of PEEK as an extracoronal attachment material in attachment retained removable partial denture induced led stresses compared to zirconia.