Effect of Low Hydroxyapatite Loading Fraction on the Mechanical and Tribological Characteristics of Poly(Methyl Methacrylate) Nanocomposites for Dentures.

Ahmed Fouly,El-Sayed M Sherif,Ahmed Mohamed Mahmoud Ibrahim,A.H Badran,Ahmed M.R Fathel-Bab

doi:10.3390/polym13060857

Ahmed Fouly, El-Sayed M Sherif + Show 3 more

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https://doi.org/10.3390/polym13060857

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Abstract

Denture base materials need appropriate mechanical and tribological characteristics to endure different stresses inside the mouth. This study investigates the properties of poly(methyl methacrylate) (PMMA) reinforced with different low loading fractions (0, 0.2, 0.4, 0.6, and 0.8 wt.%) of hydroxyapatite (HA) nanoparticles. HA nanoparticles with different loading fractions are homogenously dispersed in the PMMA matrix through mechanical mixing. The resulting density, Compressive Young’s modulus, compressive yield strength, ductility, fracture toughness, and hardness were evaluated experimentally; the friction coefficient and wear were estimated by rubbing the PMMA/HA nanocomposites against stainless steel and PMMA counterparts. A finite element model was built to determine the wear layer thickness and the stress distribution along the nanocomposite surfaces during the friction process. In addition, the wear mechanisms were elucidated via scanning electron microscopy. The results indicate that increasing the concentration of HA nanoparticles increases the stiffness, compressive yield strength, toughness, ductility, and hardness of the PMMA nanocomposite. Moreover, tribological tests show that increasing the nanoparticle weight fraction considerably decreases the friction coefficient and wear loss.

Highlights

Suitable mechanical and tribological characteristics allow dentures to endure forces and friction in the mouth [1]
Darbar et al [7] documented the types of denture base fractures, and they found that 29% of the fractures were in the complete upper dentures and 38% of the remaining fractures were located in the poly(methyl methacrylate) (PMMA) connectors of upper partial dentures
The void volume fraction of the samples calculated using Equation (3) did not exceed 3% at 0.8 wt.%, which is acceptable [54]. This low presence of voids might be attributed to the compression molding step and the low HA loading, which preserved the coherence among the PMMA molecules

Summary

Introduction

Suitable mechanical and tribological characteristics allow dentures to endure forces and friction in the mouth [1] Their base materials must be biocompatible and must not undergo chemical reactions potentially harmful to humans. Since 1937, poly(methyl methacrylate) (PMMA) is among the most used materials in denture fabrication due to its light weight, esthetic features, ease of processing and polishing, clinical manipulation, low cost, and stability in the mouth environment [2]. All these advantages have encouraged dentists to utilize it for decades as a denture base and dental restorative polymer [3]. Darbar et al [7] documented the types of denture base (made of PMMA) fractures, and they found that 29% of the fractures were in the complete upper dentures and 38% of the remaining fractures were located in the PMMA connectors of upper partial dentures

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Conclusion