Comparison of the mechanical properties of polyetheretherketone and polyphenylene sulfone produced by fused filament fabrication and conventional manufacturing methods for dental applications: an in vitro study

Additive manufacturing of thermoplastic polymers via fused filament fabrication (FFF) is gaining popularity because of its time and cost efficiency. Semicrystalline polyetheretherketone (PEEK) requires extensive postprocessing, whereas amorphous polyphenylene sulfone (PPSU) offers greater predictability and reliability. The purpose of this study was to compare the mechanical properties of PPSU, which is a new material for dental applications, and PEEK to evaluate the effects of different manufacturing methods on the mechanical properties of these materials. This study used a PEEK disc (Juvora Dental Disc, Juvora, UK) for subtractive CAD-CAM method-fabricated samples (PEEK-CG), a pure PEEK filament (Vestakeep i4 3DF filament, Evonik Industries AG, Germany) for FFF-fabricated samples (PEEK-3D), a pure PPSU filament (FIL-A GEHR, Gehr Plastics Inc., Germany) for FFF-fabricated PPSU samples (PPSU-3D), and a bulk PPSU material (Radel R-5000 NT, Solvay, France) for injection-molded samples (PPSU-INJ). A total of 80 samples (n = 20 per group) were tested. Half were evaluated for three-point bending (n = 10 per material), and the rest were evaluated for Vickers hardness (n = 10 per material). The Kruskal‒Wallis H test was used for between-group comparisons, and the Mann‒Whitney U test was used for pairwise comparisons (α = 0.05). PEEK-CG, with a flexural strength of 299.69 ± 12.26 MPa, a Young’s modulus of 8.92 ± 0.28 GPa, a flexural stress at 3.5% strain of 6.97 ± 0.65 MPa, and a Vickers hardness of 40.02 ± 10.38 kg/mm², significantly outperformed PEEK-3D (P < 0.05). PPSU-INJ outperformed PPSU-3D in all tests, with significant differences only in Young’s modulus (P = 0.013), with other differences not significant (P > 0.05). PEEK-3D outperformed PPSU-3D with a flexural strength of 220.75 ± 12.07 MPa, a Young’s modulus of 7.05 ± 0.94 GPa, a flexural stress at 3.5% strain of 3.94 ± 0.42 MPa, and a Vickers hardness of 21.48 ± 2.69 kg/mm² (P < 0.05). PPSU, with mechanical properties analogous to those of PEEK, meets the standards established for use in dental applications. These applications include its use as a fixed denture infrastructure, implant material, and removable denture clasps. The mechanical properties of 3D-printed PEEK and PPSU were found to be inferior to those of other methods, highlighting the need for improved additive manufacturing parameters.