Stored potential energy increases and elastic properties alterations are produced after restoring dentin with Zn-containing amalgams

Abstract

The aim of this research was to assess and quantify the mechanical and chemical behavior of sound and caries-affected dentin (CAD), after the placement of Zn-free vs containing amalgam restorations, and thermocycling. Peritubular and intertubular dentin were evaluated using, a) nanoindenter in scanning mode; the load and displacement responses were used to perform the nano-Dynamic mechanical analysis and to estimate the complex (E*) and storage modulus (E'); b) Raman spectroscopy, to describe the principal component analysis (PCA) and the hierarchical cluster analysis (HCA). Assessments were performed before restoration placement, after restoration removal, and after 3 months of storage with thermocycling (100,000cy/5 ºC and 55 ºC). When CAD was treated with Zn-containing restorations, thermocycling augmented the differences between E* and E', at both peritubular and intertubular dentin. The complex and storage modulus were minimum at intratubular dentin of CAD restored with Zn-containing restorations. The relative presence of minerals, crystallinity referred to phosphate and crosslinking of collagen increased at both peritubular and intertubular dentin of CAD restored with Zn-containing restorations. Nature and secondary structure of collagen augmented, in general, in those groups, except at ratio amide III/CH2 and AGEs-pentosidine. Hierarchical cluster analysis revealed different levels of dentin maturation, after thermocycling.