Effect of Different Fillers and Concentrations on the Flexural Strength of Heat-Polymerized PMMA Denture Base Resin

Abstract

Objective: The aim of the current study was to evaluate the effect of different nanofillers and their corresponding concentrations on the flexural strength of heat-polymerized PMMA denture base resin. Methods: A total of 110 PMMA specimens were produced according to ISO standards and divided into 11 groups (n = 10). PMMA was reinforced with titanium-dioxide (TiO₂), silicon-dioxide (SiO₂), graphitic carbon nitride (g-C₃N₄), multiwalled carbon nanotubes (MWCNTs), and cellulose nanofibrils (CNFs) at concentrations of 1 wt% and 2 wt%, while unreinforced PMMA served as the control group. A three-point bending assessment was utilized to measure the flexural strength. The results were put through analysis employing one-way ANOVA alongside Tukey's HSD post-hoc evaluations (α=.05). Results: Significant differences in flexural strength were observed among the groups (p<.05). The lowest mean flexural strength values were recorded for g-C₃N₄ (2%) (68.54 MPa) and MWCNTs (2%) (68.99 MPa). Within the TiO₂ groups, the 1% concentration (83.21 MPa) showed higher flexural strength than the 2% concentration (78.72 MPa), while CNF-reinforced PMMA demonstrated the highest flexural strength overall, with CNF (1%) demonstrating the maximum value (134.66 MPa), followed by CNF (2%) (129.94 MPa). Each experimental cohort surpassed the critical flexural strength standard specified by ISO 20795-1. Conclusions: The integration of nanofillers significantly affected the flexural strength of PMMA denture base resin. The reinforcing effect was strongly dependent on filler type and concentration. Among the tested materials, cellulose nanofibrils at 1 wt% provided the most effective reinforcement, whereas higher concentrations of several nanofillers adversely affected flexural strength.