The Effect of Thermal Cycling and Cyclic Loading on The Flexural Strength of Milled PMMA Versus 3D Printed PEEK as a Provisional Restorative Restoration

Background: Temporary restorations play a crucial role in oral rehabilitation. The development of CAD/CAM technology and 3D printing has expanded the use of polymethyl methacrylate (PMMA) and polyetheretherketone (PEEK) in the fabrication of provisional restorations. While both materials are widely used, their mechanical behavior under simulated long-term clinical conditions remains largely ununderstood. Aim: This study aims to compare the flexural strength of CAD/CAM milled PMMA and CAD/CAM 3D-printed PEEK provisional crowns that were subjected to thermocycling and cyclic loading, simulating the aging protocols designed to replicate long-term clinical use. Materials and Methods: A total of 54 provisional crowns (n = 27 per group) were fabricated from PMMA and PEEK. All specimens underwent an aging protocol consisting of 2500 thermal cycles (5°C– 55°C) and 600,000 mechanical loading cycles (50 N, 1.6 Hz). Flexural strength was assessed using a universal testing machine. Fracture load values were analyzed using descriptive statistics and compared using the Mann–Whitney U -test (p < 0.05). Results: PEEK crowns exhibited significantly higher mean fracture load values (2.441 ± 0.573 kN) than PMMA (1.860 ± 0.517 kN), with a statistically significant difference (p = 0.0004). PEEK specimens demonstrated consistent mechanical performance and ductile failure patterns, while PMMA crowns showed brittle fractures and greater variability. Conclusion: 3D printing PEEK provisional crowns demonstrated superior flexural strength compared to milled PMMA under simulated aging conditions. PEEK represents a promising material for long-term provisional use, particularly in high-load clinical scenarios. Keywords: PEEK, PMMA, flexural strength, thermocycling, CAD/CAM, 3D printing, fracture resistance