Mechanical and chemical characterisation of demineralised human dentine after amalgam restorations

• Zn-containing amalgam increased the mechanical properties of sound and CAD surfaces.
• Peaks of phosphate vibration increased in CAD, after Zn-amalgam restorations.
• Zn and Sn were encountered in caries-affected dentin, after amalgam restorations.
• Collagen crosslinking was decreased in CAD after Zn-amalgam restoration.
• Collagen in CAD improved (nature/secondary structure) after Zn-amalgam restoration.

ObjectivesThe purpose of this study was to evaluate the ability of Zn-free vs Zn-containing amalgams to induce remineralisation at the dentine interface.MethodologySound and caries-affected dentine surfaces (CAD) were subjected to both Zn-free and Zn-containing dental amalgam restorations. Dentine surfaces were studied by nano-indentation, Raman spectroscopy/cluster analysis, X-ray diffraction (XRD), field emission electron microscope (FESEM) and energy-dispersive analysis (EDX), for mechanical, morphological and chemical characterisation. Analyses were performed before and after placement amalgam restorations.ResultsZn-containing amalgams restorations promoted an increase in the nano-mechanical properties of sound and CAD surfaces. In samples from sound or CAD restored with Zn-containing amalgams, it was evidenced: (a) new mineral calcium–phosphate deposits (intratubular and intertubular) with augmented crystallographic maturity; these crystals were identified as hydroxyl-apatite, and (b) a generalised crosslinking reduction plus an increase in those values testing nature and secondary structure of collagen. It indicates an optimal preservation, molecular organisation and orientation of collagen fibrils.SignificanceZn-containing amalgams promote remineralisation of subjacent dentine, which is more evident in caries affected dentine surfaces.

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