EFFECT OF METAL OXIDE NANOPARTICLE REINFORCEMENT ON SURFACE ROUGHNESS AND MECHANICAL PROPERTIES OF HEAT CURE ACRYLIC RESINS

Abstract

1.Introduction: Poly(methyl methacrylate) (PMMA) remains the most widely used denture base resin due to its costeffectiveness and tissue-mimicking properties. PMMA is prone to fractures resulting from fatigue or accidental impact. Enhancing the properties of surface roughness, flexural strength, and impact strength are critical in improving clinical performance and longevity of the resin. Surface roughness influences plaque retention and infection risk, while flexural and impact strength determine resistance to masticatory and accidental stresses. Incorporating nanoparticles like silver (AgNP), copper oxide (CuO), and zinc oxide (ZnO) can improve these properties, though challenges remain regarding dispersion and concentration effects. 2.Objective: The aim of this in vitro study was to evaluate and compare the surface roughness, flexural strength, and impact strength of two high-impact heat-cure PMMA resins—Ivoclar and Lucitone—when reinforced with 2.5% and 5% concentrations of CuO, ZnO, and AgNP nanoparticles, processed using compression moulding technique. 3.Materials and Methods: Two heat-cured Hi impact PMMA resins—Ivoclar (PMMA Type I) and Lucitone (PMMA Type II)—were used to prepare one control (no nanoparticles) and six experimental subgroups incorporating 2.5% and 5% concentrations of CuO, ZnO, and AgNP. A total of 840 specimens (420 per resin) were fabricated and equally assigned to surface roughness, flexural strength, and impact strength tests (140 specimens each). Each test group comprised seven subgroups (n = 20). Surface roughness, flexural strength, and impact strength were measured using a surface roughness tester, universal testing machine, and Charpy impact tester, respectively. Data were analyzed in SPSS v26 using ANOVA, Tukey’s post hoc, unpaired t-tests, and the Shapiro–Wilk test, with significance set at p < 0.05. 4.Results: The highest surface roughness was recorded in Ivoclar with 5% AgNP, while the lowest was seen in Lucitone with 2.5% AgNP. Flexural strength was highest for Ivoclar with 5% AgNP and for Lucitone with 5% ZnO. Both Ivoclar and Lucitone achieved their highest impact strength values when reinforced with 5% AgNP. Statistical analysis confirmed significan  Indiant differences among several subgroups (p < 0.05), particularly with higher nanoparticle concentrations affecting mechanical outcomes. 5.Conclusion: Reinforcement of HI-PMMA resins with nanoparticles notably influenced their mechanical properties. 5% silver nanoparticles significantly enhanced flexural and impact strength, while copper oxide and zinc oxide nanoparticles contributed to improved surface smoothness. These results suggest that tailored nanoparticle integration can optimize denture base resins for enhanced durability, strength, and resistance to microbial colonization.