Influence of Silver Nanoparticle Incorporation on the Flexural Strength and Color Stability of Heat-Polymerized...

Background Polymethyl methacrylate (PMMA) remains the predominant choice for denture base fabrication, primarily due to its superior aesthetic characteristics, excellent biocompatibility with oral tissues, and straightforward processing techniques. However, its relatively low flexural strength and susceptibility to discoloration remain major clinical concerns. Silver nanoparticles (AgNPs), owing to their antimicrobial properties, have been investigated as reinforcing agents, although their influence on the mechanical and optical properties of PMMA remains inconclusive. This study evaluated the effect of different concentrations of AgNPs on the flexural strength and color stability of two heat-polymerized PMMA denture base resins. Methods Two commercially available heat-polymerized denture base resins were utilized to prepare 240 standardized PMMA specimens (DPI Heat Cure Denture Base Resin (Dental Products of India Ltd., Mumbai, India) and Pyrax Heat Cure Denture Base Acrylic Resin (Pyrax Polymars, Roorkee, India)). Each resin was divided into four groups: control, 0.5 wt%, 1 wt%, and 2 wt% AgNP incorporation (n = 30/group). Each subgroup comprised 15 specimens for flexural strength testing and 15 for color stability evaluation. Flexural strength was tested using a three-point bending method, and color stability was evaluated with a spectrophotometer (Commission Internationale de l'Éclairage (CIE) Lab* color system) before and after 30 days in artificial saliva. Data were analyzed with two-way ANOVA and Tukey's post hoc test at p < 0.05. Results AgNP incorporation significantly affected flexural strength and color stability (p < 0.001). Flexural strength decreased with increasing AgNP concentration in both resin systems, with a greater reduction observed in the Pyrax resin. Color stability was also significantly influenced, with the highest color change observed at 1 wt% AgNP concentration. Significant effects of resin type, nanoparticle concentration, and their interaction were identified for both outcome measures. Conclusions AgNP incorporation significantly altered the mechanical and optical properties of heat-polymerized PMMA denture base resins. Optimization of nanoparticle concentration requires careful consideration to maintain acceptable mechanical and aesthetic performance.