Flexural Performance and Surface Hardness of Filler-Modified PMMA Designed for Denture Base Applications

Polymethyl methacrylate (PMMA) is widely used in denture base fabrication; however, its relatively low flexural strength (FS) and durability limit long-term clinical performance. Reinforcing with nanofillers such as Halloysite nanotubes (HNTs) has emerged as a promising strategy to enhance the material's mechanical properties. This study aimed to evaluate the effect of different HNT loadings on the FS and surface hardness (VH) of PMMA denture base composites. PMMA composites were prepared using a heat-polymerised resin reinforced with treated HNTs at concentrations of 0, 1, 3, 5, 7, and 9 wt.%. To achieve uniform dispersion, the nanofillers were ultrasonically dispersed in methyl methacrylate before conventional polymerisation; the filler distribution and the effectiveness of silane functionalisation were examined through morphological and microchemical characterisation using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX). Mechanical performance was assessed by determining FS via the three-point bending test, while VH was measured using the Vickers hardness method. Statistical analysis one-way Analysis of Variance (ANOVA) followed by Tukey’s post hoc test, with significance set at p < 0.05 was performed, confirming that incorporating silane-treated HNTs significantly affected both tested properties (p < 0.05), with the highest values for FS (98.1 MPa) and hardness (20.20 kg/mm 2 ) observed at 5 wt% HNT loading, representing substantial improvements over unmodified PMMA. At higher concentrations (7-9 wt.%), a decline in properties was observed, attributed to nanoparticle agglomeration and reduced interfacial efficiency. HNT reinforcement effectively enhances the mechanical performance of PMMA denture base materials, with 5 wt.% identified as the optimal concentration. These findings support the potential application of HNT-reinforced PMMA to improve durability and clinical longevity of denture prostheses.