Special care must be taken in the orthodontic treatment of patients who are medicating with phenytoin, which has a side effect of gingival overgrowth. However, the mechanism of this side effect is not yet known in detail.Gingival overgrowth is termed hatred by inflammation, and it has been reported that when inflammation occurs during phenytoin treatment the movement of the teeth is delayed. Therefore, in the present study, it was decided to investigate the mechanisms of phenytoin by focusing on matrix metalloproteinases (MMPs) that are expressed as a result of inflammation.In this study, we demonstrated that the production of MMP-3 in TNF-α-stimulated Human gingival fibroblasts (HGFs) is suppressed by phenytoin. In addition, phenytoin suppressed the phosphorylation of NFκB in TNF-α stimulated HGFs. These results suggested that phenytoin stimulation regulated the production of MMP-3 in inflammatory HGFs, and that phenythoin stimulation involves NFκB signaling.

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DNA/protamine (D/P) complex was prepared and evaluated for new bone formation ability using a calvarial defect model in rats over 40 weeks old. Photothermal stress (42°C, 15 min) was repeated every day for up to 3 months to assess the effects of thermal stress on bone healing. Photothermal stress stimulation was carried out using a photothermal device, composed of an alginate gel containing carbon nanotubes and an irradiator supplying near-infrared light. Bone regeneration with the D/P complex was accelerated by photothermal stimulation compared with D/P complex implantation without thermal stimulation. There were no significant differences in Knoop hardness values between the newly formed bone, with or without photothermal stimulation, and peripheral bone. Microhardness measurement revealed that the regenerated bones were sufficiently mature. The results of this study suggested that photothermal stress stimulation upregulated bone regeneration induced by expression of heat shock-related molecules.

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To develop highly biologically safe dental gold-silver-palladium alloy compositions, the surfaces of 2 commercially available alloys were scraped with waterproof abrasive paper and corroded with hydrochloric acid, sulfuric acid, and artificial saliva, and the embryotoxicity of the corroded products was investigated. The embryotoxicity was evaluated based on the rate of differentiation of mouse ES-D3 cells to the mouse myocardial cells used in Embryo Stem Cell Test (EST) protocol and alkaline phosphatase (ALP) activity. Compared with that of the negative control without surface corrosion, the cell differentiation rate slightly decreased. The results of ALP activity were similar.Dental gold-silver-palladium alloys are the most frequently used dental alloys in Japan. It was clarified that it is necessary to analyze data on various gold-silver-palladium alloy prototypes and investigate alloy compositions with a low risk of embryotoxicity.

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Incomplete resin infiltration into acid-etched dentin leaves water-rich, resin-poor regions in hybrid layers that may cause degradation of resins and collagen fibrils. Incorporation of hydroxyapatite (HAp) into resins may provide a reservoir of calcium phosphate that might "backfill" water-filled voids in hybrid layers and resins. The purpose of this study was to test the hypothesis that incorporation of HAp into experimental resins can fill in microvoids with calcium phosphate. Three experimental adhesives were created by adding 0, 5 or 10wt% HAp. We carried out the following experiments: Water sorption and solubility evaluation, Evaluation of the calcium deposition inducibility, SEM observation and energy dispersive X-ray analysis, Tensile Testing. Although hydroxyapatite appears to have no effect on the ability of resin to infiltrate dentin in this study, incorporating HAp into dental adhesives may allow the formation of crystals below the hybrid layer, which could help create a stronger anchor.

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