Mechanical and chemical characterisation of demineralised human dentine after amalgam restorations

Objectives: The purpose of this study was to evaluate the ability of Zn-free vs Zn-containing amalgams to induce remineralisation at the dentine interface.

Methodology: Sound 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.

Results: Zn-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.

Significance: Zn-containing amalgams promote remineralisation of subjacent dentine, which is more evident in caries affected dentine surfaces.