Presentation Information
[P-42（E）]Fatigue Behavior of PEEK and Zirconia Occlusal Rests: Experimental and Finite Element Analysis
*Shi Qi Zou1, Natsuko Murakami1, Mana Onda1, Toshiki Yamazaki1, Kohei Komine1, Masaomi Ikeda2, Hidekazu Takahashi3,4, Noriyuki Wakabayashi1 (1. Advanced Prosthodontics, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, 2. Department of Oral Biomedical Engineering, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo, 3. Institute of Science Tokyo, 4. Department of Dental Materials and Engineering, Division of Life Dentistry, The Nippon Dental University)
[Objective]
Occlusal rests require high fatigue resistance to withstand functional loading. While rigid CoCr alloys are traditionally used, PEEK and zirconia have gained attention as metal-free, esthetic alternatives. However, the mechanical durability of PEEK as an occlusal rest remains insufficiently investigated, and zirconia may be vulnerable to brittle fracture under cyclic stress. This study evaluated the fatigue behavior of CAD/CAM fabricated PEEK and zirconia occlusal rests.
[Method]
Occlusal rests were designed using dental CAD software (EXOCAD, EXOCAD GmbH), and twelve specimens were fabricated for each material: CoCr alloy, zirconia, and PEEK. Fatigue testing was conducted with an electromagnetic micromechanical tester (MMT250N, Shimadzu Corp.) under a 100 N load at 2 Hz for up to 500,000 cycles. Load–deflection data were continuously recorded. A mixed design ANOVA was performed to evaluate the effects of material (between subjects) and cycle number (within subjects), followed by Bonferroni-adjusted post hoc comparisons (α = 0.05). Finite element analysis (ANSYS Workbench 2024R2, ANSYS) was conducted to examine stress distribution patterns.
[Results and Discussion]
All specimens withstood cyclic loading without visible damage. Zirconia and CoCr showed elastic behavior with small initial deflections (24.8±0.91 μm and 23.1±0.81 μm), indicating high rigidity (Fig. 1). PEEK exhibited viscoelastic behavior with greater flexibility (119.5±14.5 μm). Significant differences were found between CoCr and PEEK and between PEEK and zirconia. In PEEK, all cycle pairs up to 1k differed significantly, whereas from 2k onward, significant differences appeared only in selected intervals. In contrast, CoCr and zirconia showed no significant differences between cycle intervals except between the initial cycle and subsequent cycles. Finite element analysis revealed stress concentration at the base of the internal surface of the occlusal rest across all materials, indicating a common mechanical vulnerability regardless of material stiffness. Within the limitations of this study, both PEEK and zirconia occlusal rests exhibited sufficient fatigue resistance to withstand simulated long term functional loading. However, because PEEK demonstrated greater flexibility and progressive deflection during cyclic loading, further studies are required to determine whether this flexibility is clinically acceptable in long term use.
Occlusal rests require high fatigue resistance to withstand functional loading. While rigid CoCr alloys are traditionally used, PEEK and zirconia have gained attention as metal-free, esthetic alternatives. However, the mechanical durability of PEEK as an occlusal rest remains insufficiently investigated, and zirconia may be vulnerable to brittle fracture under cyclic stress. This study evaluated the fatigue behavior of CAD/CAM fabricated PEEK and zirconia occlusal rests.
[Method]
Occlusal rests were designed using dental CAD software (EXOCAD, EXOCAD GmbH), and twelve specimens were fabricated for each material: CoCr alloy, zirconia, and PEEK. Fatigue testing was conducted with an electromagnetic micromechanical tester (MMT250N, Shimadzu Corp.) under a 100 N load at 2 Hz for up to 500,000 cycles. Load–deflection data were continuously recorded. A mixed design ANOVA was performed to evaluate the effects of material (between subjects) and cycle number (within subjects), followed by Bonferroni-adjusted post hoc comparisons (α = 0.05). Finite element analysis (ANSYS Workbench 2024R2, ANSYS) was conducted to examine stress distribution patterns.
[Results and Discussion]
All specimens withstood cyclic loading without visible damage. Zirconia and CoCr showed elastic behavior with small initial deflections (24.8±0.91 μm and 23.1±0.81 μm), indicating high rigidity (Fig. 1). PEEK exhibited viscoelastic behavior with greater flexibility (119.5±14.5 μm). Significant differences were found between CoCr and PEEK and between PEEK and zirconia. In PEEK, all cycle pairs up to 1k differed significantly, whereas from 2k onward, significant differences appeared only in selected intervals. In contrast, CoCr and zirconia showed no significant differences between cycle intervals except between the initial cycle and subsequent cycles. Finite element analysis revealed stress concentration at the base of the internal surface of the occlusal rest across all materials, indicating a common mechanical vulnerability regardless of material stiffness. Within the limitations of this study, both PEEK and zirconia occlusal rests exhibited sufficient fatigue resistance to withstand simulated long term functional loading. However, because PEEK demonstrated greater flexibility and progressive deflection during cyclic loading, further studies are required to determine whether this flexibility is clinically acceptable in long term use.
