As part of our study about the disinfection of impressions in dental treatment of elderly patients at home, the present study investigated the effect of immersion disinfection of alginate impressions on the dimensional accuracy and deformation of edentulous working casts in relation to the W/P ratio of alginate impression materials. Two types of alginate impression material : AROMA FINE DF III (AF III) and Jeltrate Plus (JLP), characterized by smaller or greater dimensional changes in water, were used. Impression materials were mixed at the following W/P ratio : manufacturers' instructions (std), std-0.2, and std+0.4. Impressions were immersed in 1% sodium hypochlorite solution for 10 min (1 SH), 2% glutaraldehyde solution for 30 min (2 GA), or they were not immersed in any disinfectant solutions as a control. The W/P ratio had no effect on the dimensional accuracy and deformation of edentulous working casts obtained from AF III impression disinfected by 1 SH processing.

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This study evaluated the physical properties and contamination-resistance of a newly developed denture relining material (HR) with fluorinated methacrylate monomer. In the fouling test, we used methylmercaptan solution, considered to be a major cause of breath malodor, and measured the concentration of volatile sulfur-containing compounds after 24 hours immersion. The staining, water sorption, solubility, and fouling properties of HR were significantly improved (p<0.05). No significant adverse effects of the fluorinated monomer on surface hardness or shear bonding strength of HR were found. These results suggest that HR is a useful denture relining material due to its superior contamination-resistance and adequate physical properties.

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In this study, the effects of titanium casting reaction layers on the adhesion of titanium and resin for crown and bridge were examined. The adhesion strength was measured by the compressive shearing test of the as cast and superficial casting layers cut to a thickness of 100, 200 and 300 μm using 4 kinds of commercially available resin for crown and bridge. Three commercially available investment materials were used for titanium casting. We found that the adhesion strength of the as cast was affected by adhesive monomers and components of the investment materials. The adhesion strength of the cut surface was higher for 3 kinds of resin after removing the reaction layer. The effects of the reaction layer on the adhesion strength varied with adhesive monomers.

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The influence of ozone on color tone of denture base acrylic resin was examined to determine its usefulness as a denture cleaning method. Three types of ozone cleaning were used ; ozone A : ozone (20 mg/h) was generated for 10 minutes every 12 hours, ozone B : a same quantity of ozone was generated over 24 hours a day and ozone C : a greater quantity of ozone (720 mg/h) was generated. Two commercial denture cleaners, acid-electrolyzed water and distilled water were used for comparison with the ozone treatments. Color changes of the resins after a 30-day immersion in various solutions were evaluated using a colorimeter. Discolorations of turmeric-stained resins after a 60-min cleaner immersion were also examined. There were no significant color changes detected after the 30-day treatment of resin with ozone A and B, denture cleaners and acid-electrolyzed water. Ozone B and denture cleaners did not cause any change in stained resins, but ozone C and acid-electrolyzed water achieved significant stain removal.

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Although titanium dioxide photocatalyst is usually initiated only by ultraviolet in radiation, visible light responsiveness after metal ion processing was investigated by examination of the decomposition of methylene blue pigment and optimal processing conditions were studied. The photocatalyst effect depended on metal ion/TiO₂ ratio during treatment with metal ion solution. Using a 0.3 μm powder, the optimal catalyst efficiency under visible light was obtained with a Ag/TiO₂ ratio of 30 μg/g. An antibacterial effect on Streptococcus mutans was clearly confirmed on titanium dioxide film formed by the sol-gel method on a glass plate and decorated with metal ion. Dentition bleaching was also successfully carried out. Thus visible light responsiveness and an increase in catalyst efficiency were obtained, enabling antibacterial activity and dentition bleaching. These findings suggest the applicability of photocatalyst in dental practice.

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The purpose of this study was to compare the properties of trial hard resin teeth with an enamel layer made of nanocomposite to those of conventional hard resin teeth. Mechanical properties such as flexure strength, compressive strength and hardness of the nanocomposite were significantly greater than those of the enamel layer of conventional hard resin teeth. However, because of a lack of staining resistance, about 10 wt% poylmethyl methacrylate(PMMA) powder was added to the nanocomposite. The enamel layer containing PMMA powder was inferior to that of the conventional hard resin teeth in mechanical properties. Surface roughness of the trial hard resin teeth after the abrasion test was significantly less than that of the conventional hard resin teeth. Furthermore, the plastic rod used for the abrasion test of the trial hard resin teeth showed significantly less abrasion loss than the conventional hard resin teeth. The reduced surface roughness and abrasion loss may decrease negative effects on antagonistic teeth in clinical use. The trial hard resin exhibited significantly better transparency and staining resistance than the conventional hard resin teeth. This can be explained by the features of the nanocomposite in which nanoparticles are uniformly distributed.

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To compensate for the sintering contraction of porcelain inlay processed with cold isostatic pressure, the effect of intermediate oxide addition was studied. After oxidation and firing at 970℃ for 55 sec for porcelain powder with the addition of 10 wt% of B, Si, Ti, SiO, TiO, or SnO, SnO was chosen due to its color tone and stable form. The effects of various concentrations and firing times or temperatures on dimensional change and bi-axial flexure of the inlay were investigated. The contraction decreased with increases in the SnO concentrations, showing expansion when 50 wt% or more of SnO was added. There were no significant changes when the firing time was prolonged to 5 hours or the firing temperature was raised to 1100℃. The strength decreased from 75 to 30 MPa as the SnO concentration increased from 10 to 80 wt%, although the porcelain made from original powder showed 120 MPa. The intermediate oxide addition seemed to effectively compensate for the firing contraction.

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This study evaluated the effects of adherends on retentive force (RF) using denture adhesives and home-reliners. Adherends of agar simulating oral mucosa, metal plates simulating metal base, and acrylic plates were prepared. Fourteen commercially available denture adhesive and home-reliner products consisting of four powder types, four cream types, two tape types and four cushion types, were examined. The RF to agar using the powder type was significantly smaller than those of the acrylic plate and the metal plate. The cream type did not significantly vary according adherends. Regarding the cushion type, the RF of the acrylic plate was significantly greater than those of the other adherends, and the RF of agar was significantly smaller than those of the others. The RFs using the tape type were similar to those of the cushion type. These results suggest that the RFs of denture adhesives and homereliners vary according to the adherends.

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