title: 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 of resin-dentine interface after bonding with Zn-doped self-etching adhesives. Sound dentine surfaces were bonded with Clearfil SE Bond (SEB), 10 wt% ZnO microparticles or 2 wt% ZnCl2 were added into the SEB primer (P) or bonding (Bd) for Zn-doping. Bonded interfaces were stored in simulated body fluid (24h), and then tested or submitted to mechanical loading. Microtensile bond strength testing was performed. Debonded dentine surfaces were studied by scanning electron microscopy. Remineralisation of the bonded interfaces was assessed by nano-indentation, Raman spectroscopy, 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-ZnCl2 were applied, but decreased when both ZnO and ZnCl2 were incorporated into the bonding. Ei was higher when Zn compounds were incorporated into the primer (SEB·P). ZnO promoted an increase, and ZnCl2 a decrease, of both the relative presence of minerals and crystallinity, after LC. LC increased collagen crosslinking with both SEB·P-ZnO and SEB·P-ZnCl2. The ratios which reflect the nature of collagen increased, in general, at both HL and BHL after LC, confirming recovery, better organisation, 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. Mineral precipitates nucleated in multilayered platforms or globular formations on peritubular and intertubular dentine.
authors.affiliation: University of Granada, Faculty of Dentistry, Dental Materials Section, Colegio Máximo de Cartuja s/n, 18071 Granada, Spain. Electronic address: toledano@ugr.es.
authors.forename: Manuel
authors.initials: M
authors.lastname: Toledano
authors.affiliation: University of Granada, Faculty of Dentistry, Dental Materials Section, Colegio Máximo de Cartuja s/n, 18071 Granada, Spain.
authors.forename: Fátima S
authors.initials: FS
authors.lastname: Aguilera
authors.affiliation: University of Granada, Faculty of Dentistry, Dental Materials Section, Colegio Máximo de Cartuja s/n, 18071 Granada, Spain.
authors.forename: Estrella
authors.initials: E
authors.lastname: Osorio
authors.affiliation: University of Granada, Faculty of Dentistry, Dental Materials Section, Colegio Máximo de Cartuja s/n, 18071 Granada, Spain.
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Cabello
authors.affiliation: University of Granada, Faculty of Dentistry, Dental Materials Section, Colegio Máximo de Cartuja s/n, 18071 Granada, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Toledano-Osorio
authors.affiliation: University of Granada, Faculty of Dentistry, Dental Materials Section, Colegio Máximo de Cartuja s/n, 18071 Granada, Spain.
authors.forename: Raquel
authors.initials: R
authors.lastname: Osorio
mesh_terms: D000269:Adhesives / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D003804:Dentin; D008422:Materials Testing; D055595:Mechanical Phenomena; D008863:Microspheres; D013718:Tensile Strength; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry; D015034:Zinc Oxide / Q000737:chemistry
chemical_list: D000269:Adhesives; D002712:Chlorides; D017967:Zinc Compounds; C016837:zinc chloride; D015032:Zinc; D015034:Zinc Oxide
keywords: Dentine; Load cycling; Remineralisation; Self-etch adhesives; Strength