Each dental adhesive contains a specific functional monomer that determines its actual adhesive performance to tooth tissue. 4-methacryloxyethyl trimellitic acid (4-MET) is well-known as one of the functional monomers mostly available and consequently widely used in commercial adhesives. We therefore characterized the chemical interaction of 4-MET with hydroxyapatite (HAp) using X-ray Photoelectron Spectroscopy (XPS). XPS revealed that the peak representing -COO- of 4-MET shifted to a lower binding energy, when 4-MET was adsorbed onto HAp. Deconvolution of this shifted peak disclosed two components with a peak representing unreacted carboxyl groups and ester groups, and a peak suggesting chemical bonding of other carboxyl groups to Ca of HAp. XPS spectra of HAp treated with 4-MET also disclosed the surface to be enriched in calcium and decreased in phosphorus, indicating that phosphorus was extracted at a relatively higher rate than calcium. It can thus be concluded that true chemical bonding of 4-MET with calcium present in HAp occurred, as it was proven using XPS.

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This study examined the influence of centrifugal force on the filler loading of composites using a light-polymerizing apparatus combined with a centrifuge. To assess uneven filler particle distribution resulting from specimen rotation, two low-viscosity composites (Palfique Estelite LV and Revolution Formula 2) were placed in test tubes, centrifuged, and subsequently light-polymerized with the apparatus. After each specimen was sliced into four disks (2-mm thickness), the inorganic filler content and Knoop hardness number (KHN) of each disk were determined. The results suggested that filler loading of composites could be increased by application of centrifugal force if the filler and monomer components were properly arranged.

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The effects of thermocycling at 20,000 cycles and addition of silanized spherical silica filler (SF) on resin-modified glass ionomer cement (RMGIC) restorations were investigated. A RMGIC added with an untreated spherical silica filler (UF) was used as a comparison. Marginal gaps in Class V tooth cavities, compressive strength, diametral tensile strength, flexural strength, and shear bond strengths to enamel and dentin were examined. All thermocycled samples showed decreased frequency of marginal gap formation as compared to the 24-hour samples, with reduction of 73% to 95%. At the immediate condition, after 24 hours, and after thermocycling, the addition of 10 wt% SF yielded the most favorable results in terms of marginal gap formation in Class V cavities, compressive strength, flexural strength, and shear bond strength to enamel. Diametral tensile strength and flexural strength were also increased significantly by the addition of 5 wt% SF. Further, shear bond strength tests showed that the addition of SF had no effect on bonding capability to enamel and dentin.

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This study evaluated the effect of air-blowing variables on the microtensile bond strength (μTBS) of two all-in-one adhesives. A bonding agent was applied to the flat dentin surface of extracted bovine teeth, and the surface left undisturbed for 20 seconds. Gentle or intensive air-blowing was applied for five seconds, and the adhesive photopolymerized for 10 seconds. Resin composite paste was placed and cured after each bonding treatment. Specimens were subjected to μTBS test with a crosshead speed of 1.0 mm/ min. Data were statistically analyzed using ANOVA, followed by Bonferroni post hoc test. When Clearfil tri-S Bond was bonded to dentin, the μTBS value of specimens applied with intensive air-blowing was significantly higher than that applied with gentle air-blowing (p<0.01). On the other hand, with Fluoro Bond Shake One, the μTBS value of specimens applied with intensive air-blowing was significantly lower than that applied with gentle air-blowing (p<0.01).

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This study evaluated the effect of alumina-blasting and three commercial adhesive primers on the shear bond strength of a dual-cured resin luting agent to zirconia ceramics. Two different-sized zirconia ceramic specimens were treated with or without alumina-blasting and then treated with one of three adhesive primers. Subsequently, specimens were cemented together with Linkmax HV (GC). Half of the specimens were stored in water at 37°C for 24 hours and the other half thermocycled 10,000 times before shear bond strength testing. For groups treated with either alumina-blasting or primer, shear bond strength significantly decreased after thermal cycling. For groups treated with both alumina-blasting and one of the three primers, there were no significant differences in shear bond strength before and after thermal cycling (p<0.05). It was thus concluded that the application of each of the three adhesive primers following alumina-blasting was effective for strong bonding of resin luting agent to zirconia ceramics.

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This study evaluated a new enzyme solution (SFC-V) for dentin caries removal, and obtained results were compared with Carisolv^TM. Both solutions were used with a prototype plastic instrument — this being a modified technique for Carisolv. Five carious deciduous teeth were sectioned, and both treatments were applied alternately to each half. Micro-CT observations showed that both treatments resulted in removal of the outer demineralized dentin layer: 28.6% for SFC-V and 28.2% for Carisolv. As for the remaining demineralized dentin, thicknesses of 0.27μm (SFC-V) and 0.31μm (Carisolv) were observed with no statistically significant differences. FE-SEM analysis revealed that the use of Carisolv resulted in a rougher surface; whereas after SFC-V enzymatic treatment, an organized dentin collagen network with open tubules and few signs of bacteria were observed. In summary, the experimental enzymatic solution and the modified Carisolv treatment removed comparable amounts of carious dentin but with differing resultant surface morphologies.

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The aims of this study were to evaluate the fluorine depth profiles of pure titanium (Ti), stainless steel (SUS), and polymethyl methacrylate (PMMA) modified by plasma-based fluorine ion implantation and the effects of fluorine ion implantation on contact angle, fluoride ion release, and S.mutans adhesion. Fluorine-based gases used were Ar+F₂ and CF₄. By means of SIMS, it was found that the peak count of PMMA was the lowest while that of Ti was the highest. Then, up to one minute after Ar sputtering, the presence of fluorine and chromic fluoride could be detected by XPS in the surface and subsurface layer. As for the effects of using CF₄ gas for fluorine ion implantation into SUS substrate, the results were: contact angle was significantly increased; no fluoride ion release was detected; antibacterial activity was significantly increased while initial adhesion was decreased. These findings thus indicated that plasma-based fluorine ion implantation into SUS with CF₄ gas provided surface antibacterial activity which was useful in inhibiting bacterial adhesion.

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We have previously synthesized a novel acrylic resin monomer, methacryloyloxyethyl methyl succinate (TA). The aim of this in vitro study, therefore, was to examine its influence on cell viability using L-929 mouse fibroblasts and then compare the results with MMA, EMA, and LMA. Medium containing each monomer was changed every 15 minutes as some monomers were volatile. After one hour of exposure, these mediums were replaced with a normal medium and cells were further incubated for 72 hours. IC₅₀ value for each monomer was determined, and chronological cell viability and cytomorphologic observation were evaluated. Viability was impaired in a dose-dependent manner. All monomers, except TA, tended to correlate between molecular weight and cell viability. On the other hand, TA showed excellent viability and did not impair growth abruptly. These results thus demonstrated that cellular damage by TA was much lower than that by other monomers.

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Aerosol deposition (AD coating) is a novel technique to coat solid substances with a ceramic film. The purpose of the present study was to investigate the effect of AD coating on abrasion resistance of a resin composite material. A 5-μm-thick aluminum oxide layer was created on the polymerized resin composite. The specimen was cyclically abraded using a toothbrush abrasion simulator for 100,000 cycles. Abraded surface was then measured with a profilometer to determine the average roughness (Ra) and maximum roughness (Rmax). It was found that abrasion cycling increased the Ra value of the No-AD-coating group, but decreased the Ra and Rmax values of the AD coating group. Moreover, the AD coating group showed significantly smaller Ra and Rmax values after 100,000 abrasion cycles as compared to the No-coating control group. Microscopic observation supported these findings. In conclusion, the resistance of the resin composite against toothbrush abrasion was improved by AD coating.

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Chitosan/calcium phosphate (CaP) composites composed of bioactive calcium phosphate and flexible chitosan were made by a simple mixing-and-heating method. Phase composition, morphology, and mechanical properties — including in-air and in vitro fatigue behavior — were evaluated. Experimental results showed that the chitosan matrix did not affect the crystalline phase of CaP. However, the content of CaP additive affected the three-point bending strength of the composites. A CaP/chitosan ratio of 5% by mass to volume in the composite achieved the significantly highest bending strength of 45.7 MPa. Stability of chitosan/CaP hybrid composites was apparently affected by in vitro cyclic loading. Nonetheless, when applied a loading stress of 11.4 MPa, the sample containing the optimal 5 mass/vol% CaP lasted 40 minutes in in vitro fatigue test until failure occurred. It was thus concluded that hybrid biocomposites with initial high strength might be a potential implant candidate for bone defect repair.

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The purpose of this study was to examine the effect of thermal cycling on microleakage of a fissure sealant after it was bonded with different bonding agents and polymerized with different light curing units. To this end, two bonding agents (Xeno III, iBond), three light curing units (Astralis 3, Elipar free-light, Elipar free-light 2), and a fissure sealant (Fissurit FX) were used. Microleakage was then evaluated using a dye penetration method after thermal cycling. When the fissure sealant was polymerized with Elipar free-light and Elipar free-light 2, microleakage at 10,000 cycles was significantly increased compared with that at 5,000 cycles. In terms of comparison among the curing units, the best microleakage score was observed with Astralis 3 (p<0.05). In terms of comparison between the two bonding agents, no significant differences in microleakage score were observed (p>0.05). Further, it was concluded that in order to evaluate microleakage scores appropriately, it was necessary for specimens to be subjected to thermocycling of 10,000 times or more.

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A novel scaffold material based on an alginate hydrogel which contained carbon nanotubes (CNTs) was prepared, and its mechanical property and biocompatibility evaluated. Soluble CNTs were prepared with acid treatment and dispersed in sodium alginate solution as a cross-linker. After which, the mechanical property (elastic deformation), saline sorption, histological reaction, and cell viability of the resultant nanocomposite gel (CNT-Alg gel) were evaluated. The CNT-Alg gel showed faster gelling and higher mechanical strength than the conventional alginate gel. Saline sorption amount of freeze-dried CNT-Alg gel was equal to that of the alginate gel. In terms of histological evaluation and cell viability assay, CNT-Alg gel exhibited a mild inflammatory response and non-cytotoxicity. These results thus suggested that CNT-Alg gel could be useful as a scaffold material in tissue engineering with the sidewalls of CNTs acting as active sites for chemical functionalization.

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The adverse effect of Ti on body-defense macrophage is not well understood. The aims of this study were twofold: (1) to examine the intracellular accumulation of Ti element; and (2) to measure the cell viability, superoxide dismutase (SOD) production, and TNF-α secretion of macrophage-like RAW264 cells cultured for two days in medium with 1 ppm Ti prepared from acidic ICP Ti standard solution. PIXE analysis showed that element Ti was accumulated up to 7.3 ppm in RAW264 cells when cultured in the medium with 1 ppm Ti. Further, RAW264 cells cultured in the medium with 1 ppm Ti exhibited cell viability of about 60%, SOD production of about 180%, and TNF-α secretion of about 170% relative to those of control cells cultured in the medium without Ti. It was speculated that phagocytosis of minute Ti-containing complex (mostly TiO₂) by macrophage caused oxidative stress and inflammatory reaction, leading to cell proliferation arrest and increased production of SOD and TNF-α.

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The purpose of this study was to evaluate the feasibility of using a femtosecond pulse laser processing technique to store information on a dental prosthesis. Commercially pure titanium plates were processed by a femtosecond pulse laser system. The processed surface structure was observed with a reflective illumination microscope, scanning electron microscope, and atomic force microscope. Processed area was an almost conical pit with a clear boundary. When laser pulse energy was 2μJ, the diameter and depth were approximately 10μm and 0.2μm respectively — whereby both increased with laser pulse energy. Further, depth of pit increased with laser pulse number without any thermal effect. This study showed that the femtosecond pulse processing system was capable of recording personal identification and optional additional information on a dental prosthesis.

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