Effect of simulated gastric acid on the mechanical properties of conventional and polypropylene mesh reinforced poly methyl methacrylate denture base resin.

Abstract

Aim: Sustainability of dental polymethyl methacrylate (PMMA) in acidic environments is crucial as oral pH fluctuations can degrade the mechanical properties of denture bases. PMMA strengthening with polypropylene (PP) mesh has improved mechanical properties, but its effectiveness in acidic conditions remains underexplored. This investigation aimed to evaluate the mechanical properties of PP mesh reinforced PMMA (PP-PMMA) on exposure to an acidic environment as against unreinforced denture base resin (UN-PMMA).

Settings and design: Experimental In-vitro study.

Materials and methods: A total of 120 PMMA samples were prepared as per standardized guidelines and divided into two groups as unreinforced and PP - PMMA. Prepared specimens were immersed in artificial saliva and simulated gastric acid (0.06M HCl, pH 1.2) at 37°C for 96 hours to simulate long-term clinical exposure to an acidic environment. Flexural strength, impact strength, surface roughness and microscopic characteristics were assessed with aid of universal testing machine, Izod's impact tester, profilometer and high-resolution scanning electron microscope (HR-SEM) in order.

Statistical analysis used: The data were statistically analyzed using ANOVA and independent t-test set at a significance level of P-values less than 0.05.

Results: PP-PMMA exhibited significantly higher flexural strength in simulated gastric acid (70.03±1.4MPa) compared to UN-PMMA (68.77±2.2MPa) (P < 0.05). In simulated gastric acid (HCl), PP-PMMA showed no significant difference in surface roughness compared to UN-PMMA (P = 0.29). However, in artificial saliva, PP-PMMA exhibited lower surface roughness (0.47±0.14μm) than UN-PMMA (0.56±0.08μm) (P < 0.05), indicating improved smoothness. Impact strength remained comparable between groups in both immersion conditions (P > 0.05). The presence of mesh between the layers restricted the ingress of saliva and HCl as was perceived with rougher surface in the external area.

Conclusion: PP reinforcement improved the flexural strength of PMMA in acidic environments and maintained surface roughness in acidic environments but did not significantly enhance impact strength. Polypropylene mesh reinforcement effectively reduced porosities and maintained structural integrity within the PMMA matrix. These findings suggested that polypropylene mesh reinforcement enhances the durability of denture base materials and benefits patients with gastroesophageal reflux condition.