Promotion of Nickel (Ni) Allergy by Anamnestic Sensitization with a Bacterial Component, Lipopolysaccharide (LPS), in Mice.

BACKGROUND/OBJECTIVE: Lipopolysaccharides (LPS) promote allergic responses to nickel (Ni) both in the sensitization and elicitation steps. In this study, we examine the effect of pre-sensitization to LPS on the occurrence of Ni allergy using a mouse model. METHOD: A 100 mg of LPS was injected into C57BL/6J mice intraperitoneally (ip). Three weeks later, the mice were subsequently injected with 0.3 µ moles of nickel dichloride (NiCl2) and 100 µg of CpG-DNA, which acted as an adjuvant. The mice were repeatedly immunized with the 0.3 µg of nickel sulfate (NiSO4), along with 300 µl of the adjuvant, Inject Alum (Pierce, USA). Then we examined the producing capabilities of T helper type 1 (Th1) and 2 (Th2) cytokines (interferon-gamma- (IFN)-γ and interleukin (IL)-10, respectively) from anti CD3 antibody-stimulated spleen cells. RESULTS: Pre-treatment with LPS, followed by repeated challenges with Ni2+ and adjuvants significantly enhanced the IFN-γ-producing capability of spleen cells (n=5, p<0.01); however, that could not enhance the capability of spleen cells by a single challenge with Ni2+ and adjuvants (n=5). In contrast, without LPS treatment, single or even repeated challenges by Ni2+ could not enhance the IFN-γ-producing capability. On the other hand, the IL-10-producing capability of spleen cells was not enhanced even by LPS and repeated challenges with Ni2+ and adjuvants. CONCLUSION: The solitary pre-sensitization to LPS is essential for the onset of Ni allergy by shifting the Th1/Th2 immune balance toward a Th1 dominant.

Effects of dental porcelain containing silver nanoparticles on static fatigue.

The purpose of this study was to clarify the effect of silver nanoparticles on the behavior of subcritical crack growth (SCG) in dental porcelains. Prior to occurrence of fast fracture in dental porcelains, SCG occurs and leads to strength degradation over time. SCG in dental porcelains can be characterized by the stress corrosion susceptibility coefficient, n. A higher n value means a higher resistance to SCG. In this study, porcelain disks were prepared by mixing a commercial dental porcelain powder with different concentrations of silver nanoparticles, and then air-dried and fired according to manufacturer's instructions. Stress corrosion susceptibility coefficients of powder compacts were determined using a post-indentation method. A Vickers indenter was applied to the porcelain surface, and lengths of median cracks were measured at fixed time intervals over a 24-h period to calculate n. Addition of silver nanoparticles significantly increased the stress corrosion susceptibility coefficient of dental porcelain.

Effects of adding silver nanoparticles on the toughening of dental porcelain.

STATEMENT OF PROBLEM: Dental porcelains currently used for ceramic restorations are brittle, and it is sometimes necessary to replace fractured or chipped restorations. Porcelain is fragile and exhibits elastic deformation rather than plastic deformation, leading to fracture or chipping of restorations. PURPOSE: The purpose of this study was to investigate the toughening of porcelain through the addition of silver nanoparticles. MATERIAL AND METHODS: Noritake Super (NS) Porcelain AAA modified with the addition of silver nanoparticles was used. The concentration of silver in the solution was adjusted to 100, 200, 500, and 1000 ppm (Ag100, Ag200, Ag500, and Ag1000). The Vickers hardness (Hv) and median crack length extending from the corner of each indent were measured. The fracture toughness (KIC) was calculated by the indentation method. Optical reflectance spectra were recorded by using a spectrometer in the wavelength range of 200 to 700 nm. X-ray diffraction spectroscopy, color measurement, Fourier transform infrared spectroscopy, and electron probe microanalysis were also performed. The observed values of Hv, 2a, E, and KIC were compared and evaluated with a 1-way ANOVA, followed by the Bonferroni method (α=.05). RESULTS: The addition of silver nanoparticles significantly increased the Hv of all specimens with the exception of Ag100. The median crack length was significantly smaller in Ag500 (104.5 µm, SD: 11.9) and Ag1000 (100.0 µm, SD: 5.5). Significantly higher toughness values were observed for Ag500 (1.54 MPa·m(1/2), SD: 0.05) and Ag1000 (1.51 MPa·m(1/2), SD: 0.08) than for the control (1.36 MPa·m(1/2), SD: 0.03). In terms of color difference, Ag500 (5.08, SD:1.32) and Ag1000 (5.47, SD:1.05) had values significantly greater than ΔE*=2.69. CONCLUSIONS: The addition of silver nanoparticles significantly increased the fracture toughness and Vickers hardness of the NS porcelain. A residual compressive stress was generated due to the ion exchange reaction and differential thermal expansion of the silver metal nanoparticles. However, the addition of Ag500 and Ag1000 nanoparticles led to a color change.

Addition of platinum and silver nanoparticles to toughen dental porcelain.

Several studies have investigated toughening porcelain that is layered over a frame or a core. The introduction of residual compressive stress to the surface of porcelain has been shown to be effective to strengthen it. In the present study, nanoparticles of precious metals of silver and platinum (rather than non-precious metals) were used to evaluate if they could increase the fracture resistance of porcelain. The addition of silver and platinum nanoparticles was found to improve the mechanical properties of porcelain since it increased both the Young's modulus and the fracture toughness of commercial porcelain.

Toughening of CAD/CAM all-ceramic crowns by staining slurry.

The ability of staining slurries containing silver and/or potassium compounds to enhance the mechanical properties of a leucite-reinforced glass ceramic (IPS Empress CAD) was investigated by measuring the Vickers hardness, median crack length, toughness, and compressive residual stress of specimens. A staining slurry containing potassium ions was found to increase the toughness of IPS specimens more than a staining slurry containing only silver ions when applied prior to sintering. None of the staining slurries produced any color changes. Thus, the results obtained in this study demonstrate that staining slurries increase the Vickers hardness and the fracture toughness of the surface and subsurface regions of all-ceramic IPS blocks fabricated by a CAD/CAM system without sacrificing their aesthetics.

[Relationship of the movement of mandibular condyle and occlusal force balance].

PURPOSE: The present investigation evaluated the relation between the dynamic properties of the bilateral condyle in habitual maximum opening and closing movement and the occlusal force balance with clenching force. METHODS: Nine normal adults participated in this study. The translation of bilateral condyle and the rotation of intercondylar axis in habitual maximum opening and closing movement was measured using Cadiax, (ver. 3.0). The amount of translation and the rotation were converted into percentages and plotted on a graph using the translation-rotation relative chart. The maximun difference (d) between right condyle and left condyle of translation in rotation was calculated. The maximum clenching force was measured using Dental prescale 50H, type R and Occluzer FPD-703 (Fujifilm Co., Ltd.) and the center of gravity of the occlusal force was plotted on the drawings in two dimensions (anterior-posterior, right-left). RESULTS: 1. The reproducibility of the dynamic properties of bilateral condyle in habitual maximum opening and closing movement and (d) were shown on the translation-rotation relative chart. 2. It was observed that the center of gravity of the occlusal force of a number of subjects was almost localized on the median line with right-left dimension and was localized on the molar tooth area with anterior-posterior dimension. 3. The correlation coefficient was 0.33 between the coordinate value of the center of gravity of the occlusal force with right-left dimension and the path of opening's (d). The coefficient was 0.71 between the coordinate value of the center of gravity of the occlusal force with right-left dimension and the path of closing's (d). CONCLUSIONS: The present study showed the correlation between the dynamic properties of the bilateral condyle in habitual maximum opening and closing movement and the occlusal force balance with maximum clenching force.

[Manufacture of a titanium full crown by CAD/CAM--tolerance of the cutting tool].

PURPOSE: We investigated the durability of the cutting tool(bar)that is used when creating a dental crown by using the CAD/CAM system of a computer-assisted NC machine tool. METHODS: We used the chamfer type as the shape of the dental cervical margin of the support tooth model. We also used a mold model whose shaft surfaces on both sides had an 8-degree taper. We used the CAD/CAM system of DENTAL Cadim (Advance Inc.). First, we manufactured a nonocclusion dental crown of the resin-pattern on top of the support dental model, and measured its 3-dimensional shape. Upon measuring the 3-dimensional shape, we created a pure-titanium block by using cutting bars continuously for rough processing and for finishing processing separately. Upon completion of the pure-titanium block, we measured the time required for each processing and measured the surface roughness after each processing. RESULTS: The surface roughness Ra of the rough processing became significantly worse after the fifth processing (p<0.01). Rmax became significantly worse after the sixth processing(p<0.05)and after the seventh processing (p<0.01). The surface roughness of both Ra and Rmax of the finishing processing became significantly worse after the fifth processing (p<0.05) and after the seventh processing (p<0.01). CONCLUSIONS: From the viewpoint of quality of the crown's finished surface and compatibility fitness, the number of cuttings, the number of rough processing and the number of finishing processing using the same cutting tool for making a full crown of a molar tooth should be limited to four times.