In order to decrease the polymerization shrinkage stress of resin, increase core stiffness, and reduce the treatment time needed for direct resin core construction, we proposed a new method in which megafiller is inserted into the resin core. In this study, the reinforcement effect of the megafiller was examined. Alumina and stainless steel balls of 3 or 4 mm in diameter were used as a megafiller, and were treated with silane coupling agent or metal primer, respectively. Two 3mm balls or one 4mm ball were inserted into composite resin cores of 5mm in diameter and 8mm in height. The mechanical properties of these cured resin cores were determined by a compression test. Although the compressive strength of the resin core was not changed with the insertion of megafiller, the elastic modulus and yield stress increased via its insertion, regardless of ball composition or number.

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The stability of a dental alloy surface treated with adhesive monomer by electrodeposition was evaluated. Type 4 gold alloy and cobalt-chromium alloy polished to a flat surface (Ra（0.1μm) were treated with 4-methacryloyloxyethyl trimellitate (4-MET) solution by electrodeposition. The treated alloys were stored under two different conditions (12% or 50% RH) for 1 hour, 1, 5, 15, and 30 days. The stability of the treated surfaces was evaluated by assessing the shear bond strength between the alloys and self-curing methacrylate resin, and IR spectroscopic analysis. The stability of the type 4 gold alloy surface was maintained during 1-day storage in the 12% RH condition. The stability of the cobalt-chromium alloy surface was maintained during 30-day storage in the 12% RH condition, and also maintained during 5-day storage in the 50% RH condition. The 12% RH storage condition was more effective for maintaining the stability of treated alloy surfaces than the 50% RH condition.

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To reveal the effectiveness of ultraviolet (UV)/ozone irradiation in the cleaning procedure for titanium in dental implants, we examined the effects of UV/ozone treatment on the wettability and initial cell adhesion of polished titanium. After treatment with either UV/ozone irradiation or autoclave sterilization, the contact angles and initial cell adhesion were determined using a dynamic wettability test and MTS assay, respectively. Contact angles of the UV/ozone irradiation group were significantly smaller than those of the autoclave sterilization group, but were not influenced by the irradiation time. There was no significant difference in initial cell adhesion between the UV/ozone irradiation group and the autoclave sterilization group. It was suggested that UV/ozone irradiation might be useful in the cleaning of titanium surfaces, although further clarification concerning cellular physiology is required.

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The stabilities of thermal expansion coefficient (13.5×10^-6℃) and transparency of porcelain, which are main properties, have been investigated concerning in the formations of leucite and the change of leucite to sanidine by the heat-treatment (at 850℃) of the glass powder (SiO₂ 64.1, Al₂O₃ 15.0, K₂O 10.3, Na₂O 8.5, MgO 0.3, CaO 1.2, B₂O₃ 0.6 wt%). Detailed study show that: 1. After an induction period of about 10 hours under a metastable phase, the leucite in porcelain was changed to sanidine in a stable phase. 2. The thermal expansion coefficient and transparency of porcelain drastically decreased with an increase in the amount of sanidine changed from the leucite. 3. Porcelain prepared in the mixing method of 1wt% synthetic leucite crystal powder showed no change in the thermal expansion coefficient and transparency up to 4 hours at 850℃. This makes its stability improved 4 times as much as major commercial porcelains (in which sanidine is produced in 1 hour at 800 to 950℃).

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