Evaluation of the fracture strength of CAD/CAM milled custom polyetheretherketone dental post-cores

Objective: In this study, it was aimed to compare the fracture strength and fracture types of custom made post-cores prepared from PEEK materials produced with CAD-CAM of different composition. Method: In our study, 60 human mandibular first premolar teeth with equal root length were divided into 6 groups (n=10), root canal treatments were performed and the teeth were separated from their roots 2 mm above the enamel cement border. As a result of the decoration process, a 1 mm wide shoulder step was created for the teeth and a 2 mm high ferrule was obtained. For the fracture strength test, 10 mm deep post cavities were created with 1.6 mm diameter drills on the teeth. In our study, post core groups was formed from these 6 groups; Everstick Glass Fiber Post Core(Group GF), Zirconia Post Core(Group Z), Metal(Cr-Co) Post Core (Group M), Unfilled pure PEEK Post Core(GroupUP), 80% PEEK and 20% TiO2 Filled Post Core (Group TP), 80% PEEK and 20% Ceramic Filled Post Core (Group CP). Everstick glass fiber, zirconia, chromium-cobalt (Cr-Co) metal, pure PEEK, PEEK with 20% titanium dioxide (TiO2) and PEEK posts with 20% nanoceramic content were applied to the post slots. Coping was created and cemented for the samples. Static loading was applied to the long axis of the tooth with an inclination of 135o with a universal tester. The mean fracture strength between the groups was statistically evaluated with One-Way Analysis of Variance (One-Way ANOVA) and the conditions causing the difference were determined using the post hoc Tukey HSD test. Results: According to the statistical analysis results, a significant difference was found between the groups in terms of mean fracture strength (F=7,830 and p<0.05). Z group (409.34 N) was significantly higher than UP group 286.64 N), CP group (298.00N) and TP group (280.08 N). M group (376.17 N) was significantly higher than UP group (286.64 N) and TP group (280.08 N). There was no statistically significant difference between the means of the other groups (p>0.05). While repairable fracture types are in the majority in the Z group; fracture types that cannot be repaired were found in the majority in all other groups. Conclusion: In our study, zirconia posts were the most durable group in terms of fracture strength among all groups, while the PEEK group with TiO2 content was the group with the lowest fracture strength. More studies are needed to use pure PEEK and PEEK composite materials as post material in the clinic. Key Words: Polietereterketon, fracture strength, PEEK post, post-core