Functional and molecular structural analysis of dentine interfaces promoted by a Zn-doped self-etching adhesive and an in vitro load cycling model

Abstract

The aim of this study was to evaluate if mechanical cycling influences bioactivity and bond strength at the resin-dentine interface after bonding with Zn-doped self-etching adhesives. Sound dentine surfaces were bonded with Clearfil SE Bond (Kuraray, Tokyo, Japan) (SEB), and 10 wt% ZnO microparticles (Panreac Química, Barcelona, Spain) or 2 wt% ZnCl 2 (Sigma Aldrich, St Louis, MO, USA) were added into the SEB primer (P) or bonding (Bd) for Zn-doping. Bonded interfaces were stored in simulated body fluid during 24 h, and then tested or submitted to mechanical loading. Microtensile bond strength (MTBS) was assessed for the different groups. Debonded dentine surfaces were studied by field emission scanning electron microscopy (FESEM).Remineralisation of the bonded interfaces was assessed nano-indentation, Raman spectroscopy/cluster analysis, and Masson's trichrome staining. Load cycling (LC) increased the percentage of adhesive failures in all groups. LC increased the Young's modulus (Ei) at the hybrid layer (HL) when SEB, SEB·P-ZnO and SEB·P-ZnCl 2 were applied, but decreased when both ZnO and ZnCl 2 were incorporated into the bonding (SEB·Bd). In general, Ei was higher and more uniform when Zn compounds were incorporated into the primer (SEB·P). ZnO promoted an increase, and ZnCl 2 a decrease, of both the relative presence of minerals and crystallinity, after LC. Mechanical loading increased collagen crosslinking at the interface with both SEB·P-ZnO and SEB·P-ZnCl 2 . The ratios which reflect the nature of collagen increased, in general, at both HL and BHL after LC, confirming recovery, better organization, improved structural differences and collagen quality. After loading, trichrome staining reflected a deeper demineralised dentine fringe when Zn-doped compounds were incorporated into SEB·Bd. Multiple Zn-rich phosphate deposits and salt formations were detected. 4Mineral precipitates nucleated in multilayered platforms or globular formations on peritubular and intertubular dentine.

The interrelationship of microstructure and hardness of human coronal dentin using reference point indentation technique and micro-Raman spectroscopy

“…To analyze the spectral information, smoothing and manual multiple-point baseline correction was applied to the acquired Raman spectra. Raman data was obtained based on peak intensities of the ν 1 vibration of phosphate at 960cm −1 [15], ν 1 vibration of the carbonate group (B type of carbonate) in hydroxyapatite at 1070cm −1 [16], δ vibration of C-H band at 1452cm −1 [17], and amide I band at 1667cm −1 [16]. The mineral-organic matrix ratios (960/1452 and 960/1667cm −1 ) were calculated by integrating the area under the peaks to analyze differences in the chemical composition in SD and DD [17].…”

“…The phosphate/carbonate ratio was obtained similarly to analyze differences in the mineral composition at SD and DD [18]. To assess any differences in degree of the crystallinity at SD and DD, the full-width at half maximum (FWHM) of phosphate peak at 960cm −1 was measured [16]. An ANOVA (α=0.05) was used to determine any statistical differences between the mineral/organic matrix and phosphate/carbonate ratios and FWHM for 960 cm −1 at varying dentin positions.…”

Evaluation of a Collagen-Reactive Monomer with Advanced Bonding Durability

“…Compared to natural dentin, the Raman spectra of collagen amide I and III peaks within the hybrid layer shifted in the CBA group, which indicates a chemical reaction between the adhesive and collagen. Both the intensity of the pyridinium ring vibration and the ratio of pyridinium to phenyl increased within the hybrid layers created by CBA, indicating increased collagen crosslinking (Toledano et al 2015).…”

Silver improves collagen structure and stability at demineralized dentin: A dynamic-mechanical and Raman analysis

“…The raise of CH2, Amide I and Ratio Amide I/A-III (Table 2) when Ag-NPs were applied indicated recovery [32], better organization, improved structural differences and collagen quality [33]. Then, Ag-NPs application would favor further mineralization, at the long term, because of the increase of collagen crosslinking [34].…”