The aim of this study was to analyse the extent of polymerization of different adhesive films in relation to their permeability. One adhesive of each class was investigated: OptiBond FL; One-Step; Clearfil Protect Bond; and Xeno III. Adhesive films were prepared and cured with XL-2500 (3M ESPE) for 20, 40 or 60 s. Polymerization kinetic curves of the adhesives tested were obtained with differential scanning calorimetry (DSC) and data were correlated with microhardness. The permeability of the adhesives under the same experimental conditions was evaluated on human extracted teeth connected to a permeability device and analysed statistically. The results showed that the extent of polymerization obtained from DSC exotherms was directly correlated with microhardness. An increased level of polymerization after prolonged light-curing was confirmed for all adhesives. Simplified adhesives exhibited a lower extent of polymerization and showed incomplete polymerization, even after 60 s. An inverse correlation was found between the degree of cure and the permeability. This study supports the hypothesis that the permeability of simplified adhesives is correlated with incomplete polymerization of resin monomers and the extent of light exposure. These adhesives may be rendered less permeable by using longer curing times than those recommended by the respective manufacturer.

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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.

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Glass ionomer cements (GICs) are being used for a wide range of applications in dentistry. In order to overcome the poor mechanical properties of glass ionomers, several modifications have been introduced to the conventional GICs. Nanotechnology involves the use of systems, modifications or materials the size of which is in the range of 1–100 nm. Nano-modification of conventional GICs and resin modified GICs (RMGICs) can be achieved by incorporation of nano-sized fillers to RMGICs, reducing the size of the glass particles, and introducing nano-sized bioceramics to the glass powder. Studies suggest that the commercially available nano-filled RMGIC does not hold any significant advantage over conventional RMGICs as far as the mechanical and bonding properties are concerned. Conversely, incorporation of nano-sized apatite crystals not only increases the mechanical properties of conventional GICs, but also can enhance fluoride release and bioactivity. By increasing the crystallinity of the set matrix, apatites can make the set cement chemically more stable, insoluble, and improve the bond strength with tooth structure. Increased fluoride release can also reduce and arrest secondary caries. However, due to a lack of long-term clinical studies, the use of nano-modified glass ionomers is still limited in daily clinical dentistry. In addition to the in vitro and in vivo studies, more randomized clinical trials are required to justify the use of these promising materials. The aim of this paper is to review the modification performed in GIC-based materials to improve their physicochemical properties.

Water sorption decreases the mechanical properties and the bond strengths of resin-bonded dentine. The aim of this study was to evaluate the micropermeability of several self-etching and etch-and-rinse adhesives. Optibond FL, Silorane, Scotchbond 1XT, G-Bond, and DC-Bond were bonded under simulated pulpal pressure. A 10 wt% solution of ammoniacal silver nitrate and a 1 wt% solution of rhodamine B were injected into the pulp chamber at 20 cm of water pressure. The dentine-adhesive interfaces were examined using a confocal scanning microscope. Micropermeability was detected in all the adhesives. DC-Bond, G-Bond, and Scotchbond 1XT showed voids along the resin-bonded interface. Silorane and Optibond FL showed an adhesive layer that was free from water trees and micropermeability. The double staining technique is a method that gives accurate results in the study of the resin-dentine micropermeability. Each class of adhesive has a different distribution of micropermeability. The higher the micropermeability, the higher the risk of defects at the resin-dentine interface, which may represent the pathway for hydrolytic and enzymatic degradation of resin-dentine bonds over time.