Effect of mechanical reinforcement using nano-clay and acrylic impact modifiers on PMMA denture base: Evaluating...

Denture base fractures are a common clinical problem due to the inherent brittleness and low fracture toughness of polymethyl methacrylate (PMMA). This study assessed whether incorporating nanoscale clay particles and acrylic impact modifiers (AIM) could improve the mechanical properties (fracture toughness, flexural strength, elastic modulus) of PMMA denture base resin.

PMMA specimens were prepared with varying weight percentages of nanoclay and AIM, individually and in combination. Fracture toughness, flexural strength, and elastic modulus were measured using standard mechanical tests (notched-beam and three-point bending). Microstructural features were examined by scanning electron microscopy (SEM). Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's post-hoc test (α = 0.05).

AIM alone (2% by weight) increased fracture toughness by 39% (to approximately 2.07 MPa·m^1/2, p ≤ 0.05) compared to unmodified PMMA. Nanoclay at 0.25 wt% (0.25% by weight) also improved fracture toughness; higher nanoclay contents reduced it. Hybrid reinforcements yielded modest fracture toughness gains at optimal combinations but did not improve flexural strength. All reinforced samples showed slightly lower flexural strength than unmodified PMMA. SEM revealed uniform dispersion of additives and toughening interactions at the polymer-additive interfaces.

The marked increase in fracture toughness suggests to enhance the resistance of PMMA against the crack propagation and impact failure in reinforced PMMA. In clinical use, this enhanced fracture toughness may improve resistance to accidental impacts or high-load fractures. These modifications could extend the service life and improve the clinical durability of acrylic denture bases, despite a minor trade-off in flexural strength.