Effect of Type and Concentration of Nanoclay on the Mechanical and Physicochemical Properties of Bis-GMA/TTEGDMA Dental Resins.

J J Encalada-Alayola,Y Veranes-Pantoja,J A Uribe-Calderón,J V Cauich-Rodríguez,J M Cervantes-Uc

doi:10.3390/polym12030601

J J Encalada-Alayola, Y Veranes-Pantoja + Show 3 more

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https://doi.org/10.3390/polym12030601

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Abstract

Bis-GMA/TTEGDMA-based resin composites were prepared with two different types of nanoclays: an organically modified laminar clay (Cloisite® 30B, montmorillonite, MMT) and a microfibrous clay (palygorskite, PLG). Their physicochemical and mechanical properties were then determined. Both MMT and PLG nanoclays were added into monomer mixture (1:1 ratio) at different loading levels (0, 2, 4, 6, 8 and 10 wt.%), and the resulting composites were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and mechanical testing (bending and compressive properties). Thermal properties, depth of cure and water absorption were not greatly affected by the type of nanoclay, while the mechanical properties of dental resin composites depended on both the variety and concentration of nanoclay. In this regard, composites containing MMT displayed higher mechanical strength (both flexural and compression) than those resins prepared with PLG due to a poor nanoclay dispersion as revealed by SEM. Solubility of the composites was dependent not only on nanoclay-type but also the mineral concentration. Dental composites fulfilled the minimum depth cure and solubility criteria set by the ISO 4049 standard. In contrast, the minimum bending strength (50 MPa) established by the international standard was only satisfied by the dental resins containing MMT. Based on these results, composites containing either MMT or PLG (at low filler contents) are potentially suitable for use in dental restorative resins, although those prepared with MMT displayed better results.

Highlights

Dental resin-based composites (RBCs) for both direct and indirect dental restorations have been in use for the past 50 years [1]
Bisphenol A glycidyl methacrylate (Bis-GMA) is the base-monomer most frequently used in the formulations of dental restorative materials since it reduces polymerization shrinkage and enhances both modulus and thermal stability of the resulting materials; it exhibits a high viscosity, which yields usually a heterogeneous material and problems during handling and application of the product
The monomers used for the preparation of the dental composites were Bisphenol A glycidyl methacrylate (Bis-GMA) and tetraethylene glycol dimethacrylate (TTEGDMA)

Summary

Introduction

Dental resin-based composites (RBCs) for both direct and indirect dental restorations have been in use for the past 50 years [1]. These materials are composed of inorganic particles (conferring most of the mechanical properties to the final material), which are embedded into an organic matrix (consisting of a mixture of crosslinking monomers, a photoinitiator system and other additives, which form a dense cross-linked polymer upon a free-radical copolymerization) [1,2]. Bisphenol A glycidyl methacrylate (Bis-GMA) is the base-monomer most frequently used in the formulations of dental restorative materials since it reduces polymerization shrinkage and enhances both modulus and thermal stability of the resulting materials; it exhibits a high viscosity, which yields usually a heterogeneous material and problems during handling and application of the product. Gloss retention, elastic modulus, flexural strength, diametral tensile strength and reduced polymerization shrinkage have been improved by the addition of nanoparticles to dental composites [5,6]

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