Comparison of Flexural Strength and Surface Hardness of Polymethyl Methacrylate Resin Reinforced with Silanised Aluminium Oxide Nanoparticles- An In-vitro Study

Introduction: In complete denture fabrication, the common denture base material used is heat activated Polymethyl Methacrylate (PMMA). Considering various advantages, still there are some disadvantages like poor flexural strength and poor wear resistance. The flexural strength of any material reflects its potential to resist catastrophic fracture under a flexural load. Another property that influences the surface characteristics of acrylic resins is the surface hardness, which indicates the ease of finishing a material and its resistance to in-service scratching during cleaning procedures and exposure to various oral fluids. Thus an ideal denture base material should exhibit greater flexural strength and high surface hardness for the longevity of the dentures. Aim: To evaluate the effects of adding different percentages of silanised aluminium oxide (Al2O3) nanoparticles on the flexural strength and surface hardness of a conventional heat-polymerised acrylic resin. Materials and Methods: The in-vitro experimental study was conducted between October 2020 to Janaury 2021 at Drs. Sudha and Nageswara Rao Siddhartha Institute of Dental Sciences, Vijayawada, Andhra Pradesh, India. A total of 120 samples were fabricated and were grouped into four groups coded A to D (n=30). Group A was the control group (without adding Al2O3). Specimens in the other three groups (B to D) were reinforced with silanised Al2O3 at loadings of 1%, 2.5% and 5% w/w. Flexural strength was assessed with a three-point bending test using a universal testing machine. Surface hardness test was conducted using a Vickers Hardness (VH) tester. Data was analysed using Analysis of Variance (ANOVA) and Tukey’s post-hoc test. Results: Among all the reinforced groups highest flexural strength value was seen in Group C- PMMA+2.5% w/w silanised aluminium oxide nanoparticles reinforced group (88.33 Mpa) and highest surface hardness value was seen in the Group D- PMMA+5% w/w silanised Aluminium oxide nanoparticles reinforced group (29.44 VH). Conclusion: Reinforcement of the conventional heat cured acrylic resin with 2.5% w/w silanised Al2O3 nanoparticles significantly increased its flexural strength and hardness.