Uso das cargas nanométricas na modificação e preparação de resinas odontológicas.

Abstract

In this study, organophilic clay was used in the modification of a commercial microhybrid dental resin to prepare nano hybrids dental with silica nanoparticles, with the purpose to obtain a restorative material with morphological, mechanical, biological and aesthetic properties similar to commercial dental nanocomposites. The modification of the resin Z100 was performed by the mechanical mixing this resin in digital amalgamator with 1.7 phr of Cloisite 20A (C20A). The monomer bisphenol A glycidyl methacrylate (Bis-GMA) was used in the preparation (synthesis) of dental resins, which was mixed with the diluent Single Bond 1:1. The silane coupling agent and the agent of the polymerization photoinitiator camphorquinone were added to this mixture. Two groups of samples were synthesized with this system monomer / diluent / photoinitiator of polymerization agent / coupling agent (dental polymeric matrix): one group was prepared by mechanically mixing the polymer matrix with 10, 20 and 30 phr of C20A whilst another organoclay group was prepared by mechanical mixing of two polymeric fillers (silica and C20A) in 1:1 ratio, mixing the contents with corresponding loads 10, 20 and 30 phr. Both the modified resin and the resins synthesized were characterized by X-ray diffraction (XRD), Vickers hardness (HV), three-point flexural strength, microtensile microshear, optical microscopy (OM), electron scanning microscopy (ESM), spectroscopy Infrared (IR) and ultraviolet spectroscopy (UV-VIS) and cytotoxicity (MTT). The XRD patterns showed that the incorporation of 1,7 phr of the resin C20A Z100 did not result in the formation of nanocomposites. On the other hand, incorporation of the mixture of C20A and C20A and silica-based matrix Bis-GMA suggest the formation of nano composites mainly with intercalated morphology. Because microhardness values presented by dental resin containing only C20A cargo were much lower than those of the resin Z100 they have not been evaluated for other mechanical properties. The results of flexural strength were lower for the modified nano hybrid (Z100C1,7) compared to the Z100 resin. However, in other mechanical properties evaluated (microtensile, shear and microshear), this nanohybrid modified resin and nanohybrids R5C5Si, R10C10Si, R15C15Si were similar to Z100 and Supreme. The micrographs in OM and SEM revealed that this incorporation allowed a similar morphology between nanohybrid composites and commercial Z100 and Supreme, and this load did not change the color of the nano hybrid composites, as evidenced UV-vis spectra. MTT assay proved that the nanohybrids showed cytotoxicity significantly higher than Z100 and Supreme composites. Therefore, it is evident that it is possible to prepare nanoparticulate dental resins from a commercial microhybrid using a diluent prior to entering the power nanocarga in the organic matrix of the hybrid, as well as dental resins can be prepared with similar mechanical properties to biological and morphological commercial resins by a simple method of preparation with organoclay and silica incorporated into the monomer Bis-GMA, with a low cost, making them more commercially competitive.