Shika zairyo, kikai = Journal of the Japanese Society for Dental Materials and Devices最新文献

Transverse strength and acoustic emission (AE) characteristics were measured by the transverse test in deionized water at 37 degrees C on commercial denture base resins (five heat-cured type resins and one polysulfone). Difference in flexural property of five heat-cured denture base resins was not shown from the transverse deflection according to JIS, but high toughness of polysulfone was recognized in transverse deflection, flexural strength, flexural modulus, flexural rigidity, flexural proof stress, and fracture energy. The five heat-cured denture base resins showed a low AE activity, but the polysulfone resin high AE activity. Significant rates of AE for polysulfone were detected at a kgf of approximately 50-60% the maximum load. The presence of Kaiser effect in its cycle transverse test was confirmed.

Dissolution of components from pure Ni, pure Ti, NiTi alloy and 316 L stainless steel was examined in Eagle's minimum essential medium to evaluate the effects of dynamic condition, pH, extraction period and filtration on the corrosion behaviour. Extraction medium was pH 3.5, 7.0 and 9.5. Extraction was done under static and gyrating conditions of 160 rpm, 200 rpm and 230 rpm for 3 and 7 days. Under static conditions, nickel was eluted from pure Ni and NiTi alloy at pH 3.5. Nickel and iron were slightly eluted from 316 L stainless steel at pH 3.5. However, dissolution of components from alloys was greater under dynamic conditions and with longer extraction periods. Dissolution of components, particularly of nickel at pH 3.5, was the highest from pure Ni, NiTi alloy and 316 L stainless steel. Following filtration with a 0.22 micron filter, the amount of metal decreased. Titanium was not detected in the filtrate under the conditions tested. The finding that a considerable amount of nickel was detected in the extract and filtrate indicated that the element was present in both a soluble and particulate form, especially at pH 3.5. The present results demonstrate that extraction under dynamic conditions is useful for investigating the degradation of metallic materials for medical and dental use.

The disintegration of glass ionomer cements was evaluated with referred to the amounts of component elements of powders dissolved into solutions at various starting times of immersion. Glass ionomer cement products, three for luting and three for filling, were used. The starting times of immersion in solutions were; setting time and 10, 30 and 60 minutes and 24 hours after start of mixing. After the immersion in 30 ml of distilled water and physiological saline solution for 1 week, these solutions were analyzed by an atomic absorption spectrophotometer to determine the amounts of Ca, Al and Si. The amount of each element dissolved was highest when immersion in the solutions was started at the setting time except for Ca dissolved in physiological saline solution, and it tended to decrease as the start of immersion in the solutions was delayed. Some products contained Sr instead of Ca. The results indicated that glass ionomer cement should be protected from exposure to oral fluids for about 30 minutes in clinical use.

Radiopaque monomers were synthesized to examine their properties and the physical properties of their bulk polymers, to obtain basic data for new radiopaque filling composite resin. Octachlorocyclotetraphosphazene (P4N4Cl8) was used as material to be synthesized, and 2,4,6-tribromophenol, (Br3C6H2OH) and 2,4-dibromophenol (Br2C6H3OH) were selected as organic compounds having radiopacity. As a polymerizing functional group, 2-hydroxyethylmethacrylate (HEMA) was used. Radipaque monomers were synthesized as follows: 1 Cl of P4N4Cl8 was replaced by 1 mol of 2,4,6-tribromophenol, or 2 Cls by 2 mols of 2,4-dibromophenol, and the remaining 7 or Cls were replaced by HEMA, polymerizing functional group, to obtain 2 kinds of radiopaque monomers; 4 PN-(Br3Ph)1-(EMA)7 and 4 PN-(Br2Ph)2-(EMA)6. The specific gravity of these monomers was 1.4629 and 1.4978, refractive index 1.5315 and 1.5423 and viscosity, 70 and 80 poise respectively. Radiopacity was measured by an X-ray apparatus. Al equivalent, of specimen, 10 phi x 3 mm, 4 PN-(Br3Ph)1-(EMA)7 was 5.8 mm and 4 PN-(Br2Ph)2-(EMA)6 7.0 mm. 4 PN-(Br3Ph)1-(EMA)7 and 4 PN-(Br2Ph)2-(EMA)6, both wet specimens, had compressive strength of 83.7 and 81.3 MPa, in transverse strength of 45.5 and 53.0 MPa and knop hardness of 25.8 and 22.6 respectively. After 7 days, 4 PN-(Br3Ph)1-(EMA)7 had water sorption of 1.46 wt%, and 4 PN-(Br2Ph)2-(EMA)6, 0.84 wt%, and solubility of 0.15 and 0.14 wt%, respectively.

The quantity of the remaining double bonds (RDB) in polymerized visible light cured resins has been determined. Five trial unfilled resins, eight commercial composite resins and three commercial crown and bridge resins were investigated by Fourier transform infrared spectrophotometer with the liquid-film method. Infrared absorbance was measured before irradiation and at various times after irradiation. The quantity of RDB was determined and the data expressed as percentage of the total amount of double bonds in the unpolymerized resins. The quantity of RDB of five trial unfilled resins decreased linearly corresponding to the logarithmic time after the start of irradiation. The difference in the quantity of RDB at 5 min and decreasing rate of RDB could be seen in accordance with the kind of monomer. Among five trial unfilled resins, one with BMPEPP (BPE-200) used as monomer gave the smallest RDB, and one with 4 PN-(TF)2-(EMA)6 used as monomer gave the largest value. The quantity of RDB in the unfilled resin with Tri-EDMA at 5 min decreased in accordance with the irradiation time, but after 1 month, it showed almost the same value irrespective of the irradiation time. The quantity of RDB of commercial composite resins and crown and bridge resins decreased linearly corresponding to logarithmic time. In all commercial resins, the quantity of RDB became small when the base monomer was Bis-GMA but large when it was UDMA.

To predict the presence and thickness of the acid-proof dentin layer by the method of combining the halogenated methacrylate and electron-probe microanalyzer (EPMA), 2-methacryloyloxyethyl hydrogen chloromaleate (CIMEM) used as a base monomer for a bonding agent and 2-bromoethyl methacrylate (2 BEM), 2-(4-bromophenyl)ethyl methacrylate (BPy1EM), 2-(4-bromo-1-naphthyl)ethyl methacrylate (BNEM) and 2,4,6-tribromophenoxy methacrylate (TriBr-PM) used as tracers were synthesized. The bond strength to dentin treated with 37% phosphoric acid solution for 30 sec. was not statistically different for the bonding agents with and without tracers. The SEM micrographs revealed that the layers, which may be acid-proof dentin layers, were 3-4 microns thick at the resin-dentin interface for all bonding agents. According to EPMA analysis, cps of C1Ka and BrLa increase at the same points and the acid-proof dentin layer thickness was about 4 microns.

Hardened gallium alloys were analyzed by scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The cores, matrix and white irregular shape phases were visible with SEM. The round or irregular shape cores contained Ag, Pd, Cu and Zn but did not contain Ga and In. The dark irregular shape matrix, which surrounded the core, consisted of Ga-Ag, Ga-Pd, Ga-Cu and Ga-Sn phases. However, the amount of Ga-Sn phase was very low. The white phase in the matrix was Ag-In phase.

The reaction of Fe3+ and tannic acid was used in a new visual method to confirm the Fe3+ incorporated with dentin during the pretreatment with a 10% citric acid-3% ferric chloride solution or EDTA ferric ammonium salt solution. The combination of Fe3+ and tannic acid was also effective to investigate the state of incorporated resin (resin tags and resin reinforced dentin) with the dentin. The adhered dentin treated by staining with tannic acid was examined. The incorporation of Fe3+ with dentin enhanced the monomer infiltration and resulted in a high bond strength. Addition of 4-META into the MMA-TBB resin increased the resin content in dentin by promoting the rate of monomer diffusion.

Mixed silanes, 3-mercaptopropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane, were used as a primer for adhesion of poly(methyl methacrylate) to stainless steel and glass plate. The tensile bond strength of the resin to those substrates was measured after immersion in water at 37 degrees C for 3 days. The mean bond strengths of the resin to the stainless steel and to the glass plate were 23 and 17 MPa, respectively. In addition, cohesional fracture of the resin occurred in both cases. The mixture of the silanes was highly adhesive for the stainless steel and the glass plate surface treatment.

A visible light-cured composite resin was developed. Cyclophosphazene monomer, 4 PN-(TF)1-(EMA)7 was prepared as a monomer. The ratio of brush abrasion, mechanical properties, water sorption, thermal expansion coefficient and the surface of abrasion were examined after mixing with fillers of different particle size (R-972, OX-50 and VL-30). The ratio of brush abrasion showed a tendency to be small when more than 50 wt% of VL-30 with a large particle size was mixed with 4 PN-(TF)1-(EMA)7 monomer. However its abrasion surface was rough compared with that of the microparticle filler. When the microparticle filler (50 wt% of OX-50) was mixed with the monomer, its mechanical properties were good for the mixture with 50 wt% OX-50. In that case, the ratio of brush abrasion was 0.268, compressive and transverse strength, 124.3 and 86.3 MPa respectively, hardness, 43.2 Hk, water absorption 14.2 micrograms/mm3 and thermal expansion coefficient, 47.4 x 10(-6)/degrees C.