In vitro comparative evaluation of the flexural strength of acrylic denture bases reinforced with nano-PEEK and PEEK–zirconia composites

Abstract Poly(methyl methacrylate) (PMMA) is the most widely used denture base material but exhibits limited fracture resistance under functional loads. This study investigates the effect of incorporating zirconia (ZrO₂) and polyether ether ketone (PEEK) nanoparticles on the structural and mechanical properties of PMMA. Thirty rectangular heat-cured PMMA specimens (65 × 10 × 2.5 mm) were divided into three groups: Group C (control): unmodified PMMA; Group P: PMMA with 5% PEEK nanoparticles; and Group ZP: PMMA with a hybrid of 2.5% ZrO₂ and 2.5% PEEK nanoparticles. Nanoparticle morphology was analyzed by field emission scanning electron microscopy (FESEM), showing PEEK sizes between 26–100 nm and spherical ZrO₂ with a mean diameter of 47 nm. Energy-dispersive X-ray spectrometry (EDXS) was performed on ZrO₂ only. FTIR analysis confirmed interfacial bonding in the hybrid composite. Flexural strength was measured via a three-point bending test. The ZP group exhibited the highest flexural strength (mean: 139.78 MPa), significantly outperforming both P and C groups (p < 0.05), with no significant difference between P and C. The synergistic addition of ZrO₂ and PEEK nanoparticles significantly improved the mechanical and structural behavior of PMMA, offering a promising strategy to enhance durability and clinical performance of denture base materials in prosthodontics.