Therapeutic effects of novel resin bonding systems containing bioactive glasses on mineral-depleted areas within the bonded-dentine interface

Abstract

This study aimed in evaluating the effects of two experimental resin bonding systems containing conventional Bioglass 45S5 (BAG) or Zinc-polycarboxylated bioactive glass (BAG-Zn) micro-fillers on the resin-bonded dentine interface after storage in a simulated body fluid solution (SBFS). Three resin bonding systems were formulated: Resin-A: (BAG containing); Resin-B; (BAG-Zn containing); Resin-C (no filler). The ability of the experimental resins to evoke apatite formation was evaluated using confocal Raman spectroscopy. Acid-etched dentine specimens were bonded, and prepared for AFM/nano-indentation analysis in a fully-hydrated status to evaluate the modulus of elasticity (Ei) and hardness (Hi) across the interface at different SBFS storage periods. Further resin-dentine specimens were tested for microtensile bond strength after 24 h or 3 months of SBFS storage. SEM examination was performed after de-bonding and confocal laser microscopy was used to evaluate the ultramorphology of the interfaces and micropermeability. The resin A and B showed a consistent presence of apatite (967 cm(-1)), reduced micropermeability within the resin-dentine interface and a significant increase of the Ei and Hi along the bonded-dentine interface after prolonged SBFS storage. Bond strength values were affected by the resin system (P < 0.0001) and by storage time (P < 0.0001) both after 24 h and 3 months of SBFS storage. In conclusion, resin bonding systems containing bioactive fillers may a have therapeutic effect on the nano-mechanical properties and sealing ability of mineral-depleted resin-dentine interface.

Zinc-modified nanopolymers improve the quality of resin–dentin bonded interfaces

“…Dentin mineralization at the hybrid layer has been previously assessed by different techniques (morphological, chemical, or mechanical) but mostly analyzed at the specimen surface [2,4,14]. CLSM, even when it has low image resolution, permits deep tissue imaging, and may provide a useful method if combined with a selective mineral labeling dye [15].…”

“…To get ion-exchange and mineral precipitation within the hybrid layer, different particles have been incorporated into dental adhesives: bioactive glass, Portland cement or amorphous calcium phosphate [2,3,4]. However, minerals elute from the resins, producing a rapid decrease in their mechanical properties and bond strength [4].…”

“…To ascertain for bond strength, mechanical recovery and mineral precipitation at the hybrid layer, different techniques were employed: a confocal laser microscopy (CLSM) analysis with a double-dying technique (rhodamine-B/fluoresceine) informs about the adhesive penetration, permeability and hybrid layer degradation at the bonded interface after 3 months [4,14]; microtensile bond strength was tested after 24 hours and 6 months in order to examine changes in the long-term bond strengths [2,4]. Dentin remineralization at the hybrid layer was assessed indirectly evaluating nanohardness increase at the hybrid layer, after 3 months of storage [2,4,14,6], and morphologically identifying calcium deposition by CLSM, using a selective mineral labeling dye [15]. A qualitative assessment of the collagen encapsulation was completed through Masson's trichrome staining, by observing color differences within the remineralized and non-remineralized interfacial zones after 3 months of storage [16,17].…”

A zinc chloride-doped adhesive facilitates sealing at the dentin interface: A confocal laser microscopy study

“…In 32 specimens, the pulpal chamber was filled with 1 wt% aqueous/ethanol fluorescein (Sigma-Aldrich Chemie Gmbh, Riedstr, Germany) for 3 h (Sauro et al, 2012;Toledano et al, 2013a). The rest of the molars were immersed in 0.5 wt% xylenol orange solution (Xo: Sigma-Aldrich Chemie Gmbh, Riedstr, Germany), excited at 514-nm for 24 h at 37 ºC (pH 7.2).…”

“…Confocal laser scanning microscopy (CLSM) is capable of individually exciting different 7 fluorochromes by applying selective wavelengths (Griffiths et al, 1999). CLSM allows to point out the ability of fluids to penetrate the bonded interface, thus verifying the presence of micropermeability in a bonded interface (D'Alpino et al, 2006;Sauro et al, 2012). Micropermeability correlates with the presence of porosities, and so with nanoleakage.…”