Abstract
BackgroundThe aim was to evaluate the effect of silver loaded nanoparticles (NPs) application on the triboscopic, crystallographic and viscoelastic properties of demineralized dentin. Polymethylmetacrylate-based NPs and Ag loaded NPs were applied on demineralized dentin.Material and MethodsTreated and untreated surfaces were probed by a nanoindenter to test viscoelasticity, and by atomic force microscopy to test nanoroughness and collagen fibril diameter. X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging were also used.ResultsDentin treated with Ag-NPs attained the lowest complex modulus, and the highest tan delta values after 7 days of storage. Dentin treated with undoped-NPs achieved the lowest nanoroughness and the greatest collagen bandwidths among groups. Crystals were identified as hydroxyapatite with the highest crystallographic maturity and crystallite size in dentin treated with undoped-NPs. Texture increased in all samples from 24 h to 7 d, except in dentin surfaces treated with Ag-NPs at 310 plane. Polyhedral, block-like, hexagonal or plate-like shaped apatite crystals constituted the bulk of minerals in dentin treated with Ag-NPs, after 7 d. Polyhedral or rounded/drop-like, and polymorphic in strata crystal apatite characterized the minerals when undoped-NPs were used, with more crystalline characteristics after 7 d than that found when Ag-NPs were applied. Ag-NPs application did not improve the mechanical performance of dentin and did not produce dentin remineralization. However, energy was dissipated through the dentin without showing stress concentration; contrary was occurring at dentin treated with undoped-NPs, that provoked bridge-like mineral deposits at the dentin surface.ConclusionsAg-NPs application did not enhance the mechanical properties of cervical dentin, though the energy dissipation did not damage the dentin structure. Remineralization at dentin was not produced after Ag-NPs application, though improved crystallinity may lead to increase stability of the apatite that was generated at the dentin surface. Key words:Dentin, mechanical, mineralization, roughness, silver, viscoelastic.
Highlights
To facilitate dentin remineralization and antimicrobial characteristics, dentin infiltration with cytocompatible polymeric nanoparticles (NPs), such as calcium and phosphate sequestering materials have been previously proposed [1,2,3]
At both 24 h and 7 d time points, dentin treated with undoped-NPs attained the greatest bandwidths among groups. -X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis The analysis of μXRD2 profiles of cervical dentin showed that the physical broadening full width half maximum (FWHM) of peaks at 002 (2Ɵ, 25.900o; centroid peak position Ɵhkl, 0/0/-2; I, 10977386) reflection, after observing data plotted by the reduced full width and extended height at half maximum of the phosphate band, was higher (~1.1 fold) in untreated dentin surfaces when compared with the treated groups, after 7 d of PBS storage
This study has shown for the first time that the strong interaction of Ag doped nanoparticles (Ag-NPs) with HAp structure provoked poor maturation and scarce functional remineralization with ultrafine nano-crystallites at cervical dentin; these hexagonal nanoplate crystallites, with scarce crystallinity, had preferred orientation in c-direction with tendency to agglomerate toward random orientation
Summary
To facilitate dentin remineralization and antimicrobial characteristics, dentin infiltration with cytocompatible polymeric nanoparticles (NPs), such as calcium and phosphate sequestering materials have been previously proposed [1,2,3]. At both 24 h and 7 d time points, dentin treated with undoped-NPs attained the greatest bandwidths among groups. -X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) analysis The analysis of μXRD2 profiles of cervical dentin showed that the physical broadening full width half maximum (FWHM) of peaks at 002 (2Ɵ, 25.900o; centroid peak position Ɵhkl, 0/0/-2; I, 10977386) reflection, after observing data plotted by the reduced full width and extended height at half maximum of the phosphate band, was higher (~1.1 fold) in untreated dentin surfaces when compared with the treated groups, after 7 d of PBS storage. The polymorph/polyhedral crystals were confirmed to be more amorphous in nature than that organized in strata or in rounded morphologies (Fig. 3F), as observed from the diffuse ring pattern (insets at Figs. 3E, 3F)
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