Matsumoto Dental University Repository
Not a member yet
2206 research outputs found
Sort by
石膏系急速加熱型埋没材の埋没後経過時間と加熱温度コントロールによる鋳造精度の向上
Get PDFapplication/pdfStrain due to slight misfit between an implant and superstructure increases the risk of implant fracture and resorption of supporting bone. Therefore, the accuracy of the fit of superstructures should be high. The fit accuracy of superstructures fabricated by casting is markedly affected by investment procedures and conditions. Therefore, it is extremely important to clarify changes in the setting and thermal expansion of investments with changes in the conditions of their use. We investigated the relationship between the time course of the water content of quick− heating gypsum−bonded investments after investment and the fit accuracy of castings, evaluated improvement in the casting accuracy, and obtained the following results : 1. The water content of quick−heating gypsum−bonded investments decreases with time after investment. 2. A decrease in the water content of investments reduces the fit accuracy of castings. 3. Water absorption by investments a long time after investment can improve the fit accuracy of castings. 4. The decrease in the fit accuracy of castings due to a reduction in the water content of investment materials is due to the early arrival of the investment temperature at the critical temperature for setting expansion. 5. The setting expansion of investments becomes maximal at a temperature of about 55°C. 6. When castings are preheated for 20 minutes in a hot water tank (55°C), practical application and a very accurate fit can be achieved.journal articl
Management of Immature Permanent Tooth Pit and Fissure Primary Carie
Get PDFapplication/pdf若永久歯小窩裂溝部初期齲蝕への対応法は従来から様々な方法が提唱されてきた。今回,著 者らは 臨床応用の前段階として,抜去歯の小窩裂溝部をダイヤモ ンド付きスクラッチポイ ントにて開削し,その清掃・開削状況および酸処理後の裂溝部歯面の走査 型電子顕微鏡(SEM)による観察,エックス線マイクロアナライザー(XMA)による開削後の裂溝部歯面の成分分析,実体顕微鏡による小窩裂溝填塞材の填塞状態の観察,冷熱サーマルサイクリング負荷による微細漏洩の検討を行い以下の結果を得た。1)SEM像による開削状態は,スピッツ状 を呈し,有機性残留物の存在は認められなかった。また,酸処理後の裂溝底部のエナメル小柱 が明瞭に認められた。2)XMAによる成分分析では,歯 質固有成分が著明で有機性残留物の存在は認められなかった。3)小窩裂溝填塞材の填塞状態は,裂溝開口部より底部まで充填されていた。4)冷熱サーマルサイクリング負1か月後の歯面と小窩裂溝填塞材との間にメチ レンブルーの浸透はなく,微細漏洩は認められなかった。5)裂溝部の開削は最小限に留めることがで きた。journal articl
生体材料としてのチタン材の肉厚と機械的性質の関係
Get PDFapplication/pdfThe tensile strength, proof stress, elongation, and hardness of commercially available titanium wire rods of 3, 4, and 5 mm in diameter, produced by the same manufacturer, have been reported to show differences. Therefore, producing dental implants while considering that commercially titanium has the same mechanical properties may be a cause of fracture. Furthermore, it has been reported that the amount of titanium elution is influenced by the combination of titanium materials with different microstructures. Manufacturers of dental implants need to understand and overcome these problems. In this study, the bending strength of commercial raw titanium materials with four kinds of thickness : 0.5 mm (T05), 0.8 mm (T08), 1.0 mm (T10), and 1.2 mm (T12), which were produced by the same manufacturer, was measured, and differences in the strength among each thickness were evaluated. As a result, the following conclusions were obtained : 1. Bending strength was highest in T08, and lowest in T12. 2. Proof stress was highest in T10, and lowest in T12. 3. Strain amount was highest in T12, and lowest in T05. 4. Hardness was highest in T10, and lowest in T12. 5. The microstructure showed that the size of crystal grains was largest in T12. 6. Titanium plate raw materials differ in mechanical properties clearly with the thickness, and the manufacturers should establish a quality control method and should offer the fixed quality of the material.journal articl