The purpose of this study was to evaluate the durability of resin-dentin bonds in 10-yr water-storage testing. Resin-dentin bonded bulk specimens were prepared using six commercially available resin adhesives. The resin-dentin bonded specimens were stored in water for 24 h (control group) or for 10 yr (experimental groups). After each storage period, the specimens were sectioned to make specimen beams and then subjected to a microtensile bond test. After the bond test, fractured surfaces were examined by scanning electron microscopy (SEM). In addition, interfacial observation of silver nanoleakage was performed using the backscatter electron mode of SEM. The bond strengths of four of the six adhesive systems tested decreased significantly after 10 yr. However, no significant bond-strength reduction was recorded for the other two systems. The interfacial observations showed water tree propagation in the bonding resin layer as a typical morphological change after aging for five of the six adhesives tested. Water tree propagation may be a symptom of degradation in the resin bonding layer of resin-dentin bonds.

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The purpose of this study was to investigate the effect of application time of colloidal platinum nanoparticles (CPN) on bond strength. Dentin surfaces were subjected to one of the following treatments: (A) Etching with 10% citric acid-3% FeCl3 solution (10-3 solution); (B) Etching with 10-3 solution followed by applying CPN as a primer solution for 10, 20, 30, or 60 seconds; and (C) Priming with CPN for 10, 20, 30, or 60 seconds followed by etching with 10-3 solution. An acrylic rod was bonded to each treated dentin surface using 4-META/MMA-TBB resin. Bonded specimens were sectioned into beams for microtensile bond strength testing. In groups (B) and (C), highest bond strength was obtained when dentin surfaces were treated with CPN for 30 seconds. This meant that the CPN primer solution either enhanced the penetration of resin into dentin or the degree of conversion of 4-META/MMA-TBB resin. Within the limitations of this study, treatment with 0.1 mN CPN primer solution followed by 20 seconds of water rinsing resulted in high bond strength.

This study evaluated the effect of resin monomer composition on crystal growth at the interface between the resin/bioglass composites and water. Light-cured resin that contained 2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl], 2-hydroxyethyl methacrylate, and triethylene glycol dimethacrylate with different compositions were used. Resin/bioglass composites were prepared with 40 mass% bioglass and 60 mass% resin. The resin/bioglass composites were stored in deionized distilled water for 24 h (control group) or 3-12 months (experimental groups). After water storage, the disk surfaces were examined by light- and scanning electron microscopy. Chemical states of the crystals were analyzed by laser-Raman spectroscopy and micro-X-ray diffractometry. The microscopic analysis showed crystal on the resin disks surface after six months of water storage for hydrophilic resins. However, there was no crystal formation in the control and the experimental groups of specimens of hydrophobic resins. Raman analysis showed the chemical states of the crystals formed on the resin matrix and bioglass to be different. The micro-X-ray analysis of crystals on resin disks identified them to be calcium carbonate. This crystal formation occurred in water instead of simulated body fluid. In conclusion, the resin monomer compositions affected the ability to induce crystal growth on the surfaces of disks containing bioglass.