Kenichi Koshiro

Hydrolytic Stability of Self-etch Adhesives Bonded to Dentin

Functional monomers chemically interact with hydroxyapatite that remains within submicron hybrid layers produced by mild self-etch adhesives. The functional monomer 10-MDP interacts most intensively with hydroxyapatite, and its calcium salt appeared most hydrolytically stable, as compared with 4-MET and phenyl-P. We investigated the hypothesis that additional chemical interaction of self-etch adhesives improves bond stability. The micro-tensile bond strength (μTBS) of the 10-MDP-based adhesive did not decrease significantly after 100,000 cycles, but did after 50,000 and 30,000 cycles, respectively, for the 4-MET-based and the phenyl-P-based adhesives. Likewise, the interfacial ultrastructure was unchanged after 100,000 thermocycles for the 10-MDP-based adhesive, while that of both the 4-MET- and phenyl-P-based adhesives contained voids and less-defined collagen. The findings of this study support the concept that long-term durability of adhesive-dentin bonds depends on the chemical bonding potential of the functional monomer.

Hydrolytic stability of one-step self-etching adhesives bonded to dentin.

PURPOSE To evaluate the hydrolytic stability of three one-step self-etching adhesives (1-SEAs) bonded to dentin through bond strength testing and ultra-morphological interfacial analysis before and after long-term thermocycling. MATERIALS AND METHODS Eighteen flattened mid-coronal dentin surfaces of extracted human molars were subjected to bonding treatment using three 1-SEAs (Clearfil S3 Bond, Kuraray (S3), G-Bond, GC (GB), Absolute, Dentsply-Sankin (AB)), after which the bonded surfaces were built up with composite. After storage overnight at 37°C, the specimens were sectioned into slabs and further trimmed into an hourglass shape with an interface area of approximately 1 mm2. The specimens were left untouched (control) or were thermocycled for 100,000 cycles. The microtensile bond strength (μTBS) was measured and the ultrastructure of the adhesive/dentin interface characterized using transmission electron microscopy (TEM). RESULTS Long-term thermocycling significantly decreased the μTBS of all one-step adhesives tested (p < 0.05, one way ANOVA and Games-Howell test). TEM revealed a similar interfacial ultrastructure before and after thermocycling for S3. For GB, many voids were observed at the interface after 100,000 thermocycles. Regarding AB, collagen fibrils could no longer be clearly observed upon staining, while the adjacent unaffected dentin was rich in voids. CONCLUSION The bond strength and ultramorphological data demonstrated that the bond of 1-SEAs to dentin degrades with time, although the degree of degradation is obviously material dependent.

Improved bond performance of a dental adhesive system using nano-technology

Since adhesive technology was introduced into dental field, metal-based restoration has been gradually replaced by metal-free restoration. Using the adhesive technology, minimum invasive technique has been possible in daily clinical practice as well as esthetic tooth-colored restorations have become very popular all over the world.One of the current issues of the dental adhesive is durability of bond between tooth structure and adhesive resin. Several approaches to overcome the issues have been carried out. Self-etching approach is believed to create durable bond because demineralization of superficial tooth surface is very shallow. Other approach is to utilize the inhibitor of enzymes which are suggested to catalyze the decomposition of resin composites and are always secreted within the oral environment.In the present study, Colloidal Platinum Nanoparticles (CPN) was applied before the application of 4-META/MMA-TBB resin cement as the third possibility to prolong the durability of bond. This implies that the use of the CPN solution would create higher conversion at the interface compared with conventional bonding procedures.

Expansion of nanotechnology for dentistry: effect of colloidal platinum nanoparticles on dentin adhesion mediated by 4-META/MMA-TBB.

PURPOSE To investigate the effect of Colloidal Platinum Nanoparticles (CPN) on the bond strength between dentin and 4-META/MMA-TBB resin using different concentrations of CPN. MATERIALS AND METHODS Twenty-five extracted human third molars were stored in 0.5% chloramine T. The occlusal dentin slices were prepared by grinding occlusal surfaces of each tooth and polishing with 600-grit silicon carbide paper under running water. One control and four experimental groups (2 specimens per group) were used as follows: a) dentin surfaces treated with 10-3 solution, followed by rinsing with water and subsequently an acrylic rod bonded with hand-mixed 4META/MMA-TBB resin (Super-Bond C&B, Sun Medical) (control); b) dentin surfaces treated with 10-3 etching solution, followed by rinsing with water and application of CPN (100% or 10%) as a primer solution for 60 s and rinsed with water for 20 s, then an acrylic rod bonded with Super-Bond C&B(Etch-CPN [100% or 10%]); c) dentin surfaces treated with CPN (100% or 10%) for 60 s, rinsed with water for 20 s, followed by application of 10-3 solution, then an acrylic rod bonded with Super-Bond C&B (CPN-Etch [100% or 10%]). After storage in 37°C water, specimens were sectioned into beams (cross-sectional area: 1 mm2) for microtensile bond strength testing at a crosshead speed of 1mm/min. The data were analyzed using the Games-Howell method (p < 0.05; n = 15). RESULTS Etch-CPN (100), CPN-Etch(100) and CPN-Etch (10) showed significantly higher bond strengths compared to the control. When using 10% CPN, the highest bond strength was demonstrated. The bond strength of 4META/MMA-TBB resin was approximately doubled by CPN application. CONCLUSION The results of this study showed that higher bond strengths are obtained when treating dentin with a lower concentration of CPN. Further evaluation to optimize conditions such as the application time and rinsing time are required.

Electron microscopy for imaging interfaces in dental restorations

Publisher Summary Electron Microscopy (EM) has played an important role in the field of dental biomaterials for many years. The Transmission Electron Microscope (TEM) is the instrument that is most capable of elucidating the ultra-structural morphology of the resin/tooth interface produced by dental adhesives, with high resolution and reliability. EM can be used to explore to the level of collagen fibril cross-banding in dentine, which is beyond the resolution limits of most conventional light microscopical techniques. Transmission electron microscopy involves the irradiation of the whole specimen, which is thin enough to transmit at least 50% of the incident electrons. The emergent beam of transmitted electrons is focused by a system of lenses to form a magnified, two-dimensional image of the specimen. The major advantage of transmission electron microscopy is its high resolving power.