The liquid composition of adhesive resin cement mixed with a fluoride-releasing monomer was examined to develop fluoride-releasing cement having excellent adhesiveness and physical properties. Thus, five types of liquid composites were prepared by mixing 10.0〜40.0 wt% of fluoride-releasing phosphazene monomer (synthesized monomer P₃N₃(F)₁(EMA)₅) with commercial monomers. Then, the chronological amounts of fluoride release, tensile adhesive strength between the cement and Co-Cr alloy, Ag-Pd-Au alloy and 18 Karat gold alloy, compressive strength, water sorption and solubility were measured. The results were as follows. Both fluoride release and the cumulative amounts of fluoride release increased in accordance with the increase in the ratio of the synthesized monomer. Tensile adhesive strength between the cement and three kinds of alloys decreased with the increase in the ratio of the synthesized monomer. Compressive strength showed a tendency to increase in accordance with the increase in the ratio of the synthesized monomer. Both water sorption and solubility markedly decreased in accordance with the increase in the ratio of the synthesized monomer.

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The mechanical properties of the commercial Type 4 gold alloy (Ishifuku casting gold Type 4) for casting in clinical applications were examined with the different solutionized temperatures (ST). Heating for 10 minutes at 600, 650, 700, 750, 800, 850 and 900℃ STs was followed by a hardening heat treatment Vickers hardness, tensile strength, and elongation of the hardening heat-treated alloy were found to decrease with higher STs. Cross-sectional SEM images revealed an increased void in tensile strength at 900℃. Polishing surface was brilliant and X-ray diffraction was α single phase at 700℃.

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To evaluate the cushioning effects of dry casting ring liners on the hygroscopic expansion of investment materials, cushioning ability was determined for fifteen ceramic liners (A : rockwool type, B : ceramic fiber low temperature type, C : ceramic fiber standard type, D : ceramic fiber low temperature standard type, E : kaolin type). Dry liners were seated inside the sliding frame of an apparatus for expansion measurement, and then the hygroscopic expansion was measured for 120 min. Cushioning effects were calculated by differences between the hygroscopic expansion with and without a liner. The cushioning effect of liners increased with time and peaked at 20 min, then markedly decreased by 25〜40 min, and changed only slightly thereafter. In only three liners in the D group, the cushioning effect showed a positive value by 120 min starting 15 min after the water was poured. The maximal cushioning effects of fifteen liners were noted in D group liners. The cushioning ability of three liners in D group on the hygroscopic expansion was sufficient.

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The purpose of this study was to investigate the effectiveness of surface treatment on commercial pure titanium applied by cold plasma (CP) treatment using experimentally developed equipment with a DC power supply. The treatment effect on the bonding characteristics of dental resin cement and adsorption of a primer for metal by CP treatment were also examined. SEM observation showed that CP treatment did not change the surface texture of titanium. Titanium plates contaminated with human saliva recovered by CP treatment not only for polished surfaces but also for sandblasted surfaces. IRA spectra by FT-IR indicated that CP treatment enhanced the reaction of primer to titanium in order to remove the contamination. These results suggest that CP treatment might be a suitable surface treatment to enhance the bonding characteristics of titanium in dentistry.

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A method for calculating tooth movement during orthodontic treatment is presented. Situations in which constant loads were applied to the central incisor were assessed, and it was shown that the tipping movement and bodily movement could be calculated. Next, the situation of the second molar being moved upright by a spring was calculated. The molar was subjected to a moment and an elongation force, and tipped in the distal direction. This movement pattern was almost the same as that of the initial tooth movement. In the anchorage teeth, composed by connecting the canine, the first and second premolars with a wire, by moving a tooth, a load to prevent it was applied from the wire. Redistribution of the load occurred during orthodontic treatment. It was difficult to estimate such a movement pattern from the initial tooth movement.

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The sheets of lactic acid/glycolic acid copolymer (PLGA) and its composites containing calcium carbonate and/or calcium phosphate impregnated with chlorhexidine acetate, tetracycline, tetracycline hydrochloride, minocycline hydrochloride and metronidazole were prepared. The sheets were placed in phosphate-buffered saline (pH 7.4) at 37℃ to examine the influence of the drugs and the base materials on the release of drugs and degradation of PLGA by measuring temporal changes in the release of the drugs, molecular weight of PLGA and the thickness of the sheets. The release of the drugs was considerably influenced by the types of the base materials and the drugs and different in the pattern of the release curye, one-day release percent, the time showing, accelerated release rate, and the time finishing most of the release. The influence of the type of the drugs on the degradation of PLGA was smaller than that of the base materials, in which degradation for the composite materials was slower than that for PLGA alone.

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The influences of benzoyl peroxide (BPO) concentration, molecular weight, morphology of PMMA powder and the addition of BPO to PMMA powder on polymerization of PMMA/MMA resin initiated by BPO/N, N-dimethyl-p-toluidine were examined using 20 varieties of PMMA powder with or without BPO inside the powder from the following aspects : characteristics at the time of polymerization (peak time and peak temperature), as well as molecular weight, residual monomer and residual BPO in polymerized material obtained using the thermocouple method, size exclusion chromatography and high performance liquid chromatography. It was found that : (1) the influence of morphology and molecular weight of PMMA powder on polymerization of the PMMA/MMA resin was great but that of the BPO content was relativelv small for PMMA containing BPO inside the powder particle and (2) polymerization characteristics and properties of the polymer obtained by PMMA powder admixed with BPO were different from those of the powders containing BPO.

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Three kinds of phosphate-bonded investments for cast denture base fabrication were investigated for application to the quick-heating method. Not only the quick-heating type commercial investment but also the conventional investment were successfully fabricated by quick heating. However, the mold from another conventional type exploded during quick heating. Considering the factors involved in mold explosion, the compressive strength had little efficiency. Scanning electron microscopic images suggested that the cavities formed inside the mold surface were important because internal gas might be easy to exhaust. Furthermore, there was 1ess binder in the negative investment for quick heating. When NH₄H₂PO₄ was added in the conventional investment, the investment was available for quick heating. Therefore, the internal structure the mold was a key to its availability for use with the quick heating of cast denture base fabrication by the ringless method.

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After sandblasting, pure titanium and 12% AuPdAg alloy plates were treated with super critical water (SCW) in an autoclave under 45 MPa at 450℃. Field emission-type scanning electron microscopy showed that fine particles, less than 0.2 μm, were formed on the cpTi with SCW and a thick layer formed on the surface heated to 600℃ in the air. X-ray diffractometric study revealed that TiO₂ formed on the cpTi with both the treatments, whereas no appreciable oxides were observed on the 12% AuPdAg alloy with SCW, although CuO formed on the alloy heated to 600℃ in the air. The bonding strength of two types of veneering resin to both metal plates with and without the above treatments was determined. The bonding strength of cpTi with SCW to one resin was larger than the other conditions (p<0.05). However, there were no significant effects of SCW on the bonding strength between 12% AuPdAg alloy and veneering resins (p>0.05).

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