Effect of repeated heat pressing on fracture resistance and mode of failure of Polyetherether ketone (PEEK) three-unit fixed dental prosthesis (FDP).

Objectives: to evaluate the effect of repeated heat pressing on fracture resistance and mode of failure of new and reprocessed PEEK either partially or totally 3-unit FDPs.
Methods: A total of 15 PEEK (Bredent Gmbh & Co.KG, Germany) FDPs were manufactured on stainless-steel abutments and divided to three groups (n=5). Group I was pressed using new PEEK, Group II; 50% new PEEK and 50% reprocessed PEEK, and Group III; 100% reprocessed PEEK. The FDPs were vertically loaded till failure in a universal testing machine. One-way Analysis of Variance (ANOVA) was used to compare between different PEEK conditions. The significance level was set at P ≤ 0.05. Failed specimens were examined for mode of failure and microstructural analysis with Scanning electron microscope SEM and X-ray diffraction analysis (XRD).
Results: There was a statistically significant difference between mean fracture resistance values of different PEEK conditions (P-value = 0.006, Effect size = 0.577). Pair-wise comparisons between conditions revealed that there was no statistically significant difference between new and partially reprocessed PEEK; both showed statistically significant higher mean fracture resistance than totally reprocessed PEEK.
Conclusions: Totally reprocessed PEEK three-unit FDPs had the lowest fracture resistance compared to New and partially reprocessed PEEK although all exceeded maximum occlusal forces recorded in the molar area. Incorporating reprocessed PEEK material in three-unit FDPs increased brittleness and decreased their ability to deform and absorb stresses created during force application.