This study investigated the temporal changes of dentin bond strength in dual-cured resin core foundation systems. Three core foundation systems, Estecore (EC, Tokuyama Dental), Clearfil DC Core Automix ONE (DC, Kuraray Noritake Dental) and Unifil Core EM (UC, GC), were used. The adhesive resin was applied on the surface of bovine dentin and light activated for 10 seconds. Then, core resin paste was filled onto the surface and cured (specimens with irradiation). For the specimens without irradiation, neither the adhesive nor the core resin was light activated. After 10 minutes, the specimens were immersed in water for 10, 30 or 60 minutes and 6, 12 or 24 hours, then shear bond strengths were measured. The bond strength increased over time for each system. The behavior of the changes in bond strength differed both by the system used and the irradiation conditions. In EC, the bond strength increased over time faster than the other two systems, and was not affected by the irradiation. DC and UC with irradiation showed higher bond strength than those without irradiation. The results showed that the development of dentin bond strength of resin core foundation systems is influenced by the systems used and the curing condition.

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This study investigated the effect of three dentin desensitizers, Teethmate Desensitizer (Kuraray Noritake Dental), GLUMA Desensitizer (Heraeus Kulzer) and Clinpro-XT Varnish (3M ESPE), on resin bond strength to dentin. The coronal dentin of freshly extracted human premolars was ground with #600 SiC paper and cleaned ultrasonically. One of the desensitizers was applied on the surface according to the manufacturer’s instructions. After being immersed in water for 24 hours, the dentin surface was treated with Clearfil Tri-S Bond (Kuraray Noritake Dental) and filled with Clearfil Majesty LV (Kuraray Noritake Dental) on top. After immersion in water for 24 hours, microtensile bond strength was measured. As a control, desensitizers were not applied to the dentin surface. When Clinpro-XT Varnish was applied, the bond strength was significantly lower compared with the other groups (p<0.05). There was no difference between the groups of Teethmate Desensitizer, GLUMA Desensitizer and control (p>0.05). It was concluded that Teethmate desensitizer and GLUMA Desensitizer had no influence on the resin bond strength to dentin.

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CAD/CAM composite restorations occasionally require morphologic adjustment by building up additional composite to counter excessive abrasion. However, it is difficult to achieve bonding between the CAD/CAM composite and the additional composite, because the CAD/CAM composite is highly-cured. This study investigated the effect of surface treatment on the bond strength between the CAD/CAM composite and the additional composite, in order to establish an optimum surface treatment for the additional building-up. A CAD/CAM composite Cerasmart (GC) was ground with #800 waterproof abrasive paper. The ground surface was blasted with alumina and ultrasonically cleaned in distilled water. The surface was then processed using Universal Primer (Tokuyama Dental, Up group), Universal Primer and G-Premio Bond (GC, UpG group), Ceramic Primer II (GC) and G-Premio Bond (CpG group), or ScotchbondTM Universal Adhesive (3M ESPE, Sb group). A composite, MI Fil (GC), was built up on the treated surfaces. The specimens were subjected to shear bond tests. One-way ANOVA and Bonferroni correction were performed for statistical analysis (α = 0.01, n = 10). The shear bond strength was significantly higher in the UpG, CpG, and Sb groups than in the Up group. It was clarified that silane coupling treatment followed by application of bonding agent improved the bond strength between the CAD/CAM composite and the additional composite.

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In this study, we examined the influence of atmospheric pressure low-temperature plasma treatment on the shear bond strength between adhesive resin cement and a gold-silver-palladium alloy surface contaminated with silicone oil. After sandblasting with alumina, the gold-silver-palladium alloy specimens were contaminated with a silicone disclosing material, and then the material was removed. Five experimental groups were designed in terms of surface treatment: without treatment (Cont), water rinsed (Wt), washed with absolute ethanol (Sp), sandblasted with alumina (Sb) and treated with atmospheric pressure low-temperature plasma (Ps). After stainless steel was bonded with adhesive resin cement, the specimens were subjected to shear bond testing. Moreover, in order to observe changes in the wettability of the surface, contact angles were determined. Data were analyzed by one-way analysis of variance and multiple comparison test (α=0.01). Groups Sb and Ps showed a high adhesive strength compared with the other groups. Between these two groups, no statistical difference was found. In the contact angle test, Ps showed the lowest contact angle. These results suggest that the atmospheric pressure low-temperature plasma treatment may remove contaminants on the surface of an adherent, facilitating the bonding between metals and adhesive resin cements.

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This study evaluated the effect of sandblasting on the bonding ability of an adhesive resin cement system, RelyX Ultimate/Scotchbond Universal Adhesive (3M), to CAD/CAM resin blocks (Lava Ultimate: 3M ESPE, CeraSmart: GC, Shofu HC Block: Shofu, KZR-CAD HR: Yamakin, KATANA Avencia: Kuraray Noritake Dental). The shear bond strength to CAD/CAM resin blocks after 24-hour storage was increased by sandblasting or CoJet sandblasting treatment, compared to non-sandblasted specimens. However, the effect of sandblasting or CoJet sandblasting on the bond strength differed depending on the CAD/CAM resin blocks used.

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This study observed the interfacial ultrastructure of G-Premio BOND (GC) under FE-SEM and TEM, and evaluated its clinical application. For SEM observation, human extracted molars were used. The tooth crown was horizontally cut to expose flat enamel and dentin surfaces. The surfaces ground with #1,000 SiC paper were treated with G-Premio BOND for 0 sec or 10 sec, and placed with MI GRACEFIL (GC) resin composite. The specimen was cut into halves and embedded in epoxy resin. After the cut surfaces were polished, argon-ion beam etched and Pt-sputtered, the bonding interfaces with enamel and dentin were observed under SEM. For TEM observation, the bonded surfaces created as above were ultra-thinned with and without demineralization. We also use this new restorative system in daily treatment. SEM images showed that the bonding agent created a rigid junction and no gap with enamel and dentin. TEM revealed a tight interface, but superficial interaction with dentin. The new self-etching adhesive showed satisfactory adhesion to tooth tissues and is thought to be promising for clinical use.

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