Fracture toughness values (K_Ic) obtained by different techniques are not consistent for the same materials. The aim of this study was to evaluate the relationship of numerical formula between two fracture toughness testing techniques : single-edge notched beam (SENB) and notchless triangular prism (NTP), using six dental luting cements, three kinds of resin-modified glass ionomers (RI, RV, RF), 2 kinds of conventional glass ionomers (GR, GM) and zinc phosphate cement (ZP). K_Ic of cements measured by the two tests were compared by the t-test and the correlation between the two tests was evaluated by simple linear regression analysis and Akaike Information Criterion (AIC). The K_Ic of RI, GM and ZP showed a significant difference (p<0.05) between the two tests. The relationship between two tests showed a significant correlation (R²=0.99) and its equation was K_IcN=1.23 K_IcS-0.07. Also, this same linear relationship was found by AIC. This equation suggested that K_IcN was about 1.2 times K_IcS.

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This study examined the bio-compatibility and bone-compatibility of 4 kinds of metal using rats. Non-magnetic and magnetic platinum-iron alloy, titanium and stainless steel were implanted into the tibia at 1, 2, 4, 8 and 12 weeks. Bone growth rate, maturation and growth quantity were analyzed and the influence of the static magnetic field on osteogenesis was studied. Titanium, non-magnetic and magnetic platinum iron alloy did not affect the histological findings and the distribution of Ca and P in the surrounding areas of the implant. According to the progress of time, the Ca/P index and bone growth quantity showed no significant difference. From this experiment, osteogenesis was not proven, however, there was no damage to the surrounding tissue in vivo, but the bone growth quantity was significantly larger than that of stainless steel. From these findings, non-magnetic and magnetic platinum-iron alloy excelled at bone maturation, bone growth, bio-compatibility and bone-compatibility similarly to titanium. It was suggested that the magnetic alloy can be safely used in vivo.

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In this study, forces were placed on the mandibular arch connected to a 0.016 inch square wire, and the resulting forces transmitted to the teeth were calculated by the finite element method. The force was dispersed and transmitted to adjacent teeth with tooth movement. The dispersion of force increased with an increase in tooth mobility. When force was applied to a tooth with a small root such as an incisor, about one half of the force was transmitted to the tooth, and the remaining force was transmitted to adjacent teeth. On the other hand, for a tooth with a large root such as a molar, most of the applied force was transmitted to the tooth only. When a labio (bucco) - lingual force was applied to a tooth, the dispersion of transmitted force increased, because the tooth mobility became larger than in the case of an axial force.

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To study the water-resisting property of the silanized layer at the silica-resin interface, 1-methacryloyloxymethyltrimethoxysilane (1-MMS), 3-acryloyloxypropyltrimethoxysilane(3-APS), N, N-Bis (trimethoxysilylpropyl)-methacrylicacidamide (MBPS), and 3-methacryloyloxypropyltrimethoxysilane (3-MPS) as a control were examined. The tensile bond strength of the resin composite to glass plates modified with 50mmol/l ethanol solution of each silane was measured. The tensile bond strength of one-day storage at room temperature of 1-MMS and 3-APS showed no significant difference from those of 3-MPS and no significant decreases with the time course of water storage periods. On the contrary, the tensile bond strength of 3-MPS and MBPS in water storage groups showed a significant decrease compared to the room temperature storage group. It was suggested that the silane coupling layer of 1-MMS and 3-APS had a high water resistance.

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The consistency, setting time, film thickness, compressive, diametral tensile, and shear strength of experimental temporary cements containing the pre-reacted glass ionomer (PRG) filler were examined. The experimental temporary cements containing PRG filler with and without HY agent and two different types of commercially available carboxylic temporary cements were used. The cements were mixed at three different powder-liquid ratios (the manufacturers' recommended powder/liquid ratio (MRR) and MRR+/-20%) and the cement specimens were prepared for each property measurement. The experimental cement containing HY-agent had greater consistency and longer setting time as compared to the commercially available cements. The film thickness values of both experimental cements were smaller than the commercially available cements. In particular, the experimental cement with HY-agent revealed a notably smaller film thickness. The results similar to those of the cement mixed at MRR were obtained for all cements tested when the mixing power-liquid ratio was changed. The strengths of experimental cements were comparable to those of commercially available cements.

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The dental magnetic attachment consists of a magnet assembly and keeper. The Nd-Fe-B magnet of the magnetic attachment enhances the attration to the keeper by a magnetic stainless steel yoke. The magnet is covered with the magnetic stainless steel yoke and nonmagnetic stainless steel. The joint of the magnetic stainless steel yoke and nonmagnetic stainless steel is welded seamlessly by a micro-laser. A closed magnetic circuit is formed between the magnetic assembly and magnetic stainless keeper. A strong attractive force is generated between the magnet assembly fixed in the denture and the keeper fixed in the root cap. The objectives are to review the dental magnetic attachments, magnet and magnetic stainless steels, magnetic circuit, magnetic retentive force, corrosion characteristics, and safety of the magnetic field.

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