アブストラクト（16巻2号：神奈川歯学）

神奈川歯学

Japanese

Title　： 電位差法による歯科用アマルガムの疲労試験について
Subtitle　： 原著
Authors　： 宮国敏
Authors（kana）　：
Organization　： 神奈川歯科大学保存学教室第一講座
Journal　： 神奈川歯学
Volume　： 16
Number　： 2
Page　： 157-171
Year/Month　： 1981 / 9
Article　： 原著
Publisher　： 神奈川歯科大学学会
Abstract　： 「はじめに」 アマルガムは臼歯部の歯冠部実質欠損の修復, とくに内側性窩洞に対しては優れた修復材として, 現在でも日常の臨床に多用されているが, 一方, その主要な欠点の一つとして辺縁破折の問題が指摘され, これに関しては過去に多くの基礎的ならびに臨床的研究がなされている. このような辺縁破折は不適切な仕上げ研磨により修復物辺縁に残されたアマルガムの過剰溢出部が咬合により破折するばかりではなく, 冨田によれば, 正しく填塞され仕上げ研磨されたアマルガム修復物においても研磨2週間後にはすでに辺縁部の破折が見られ, 破片によって生じた窩縁との間のギャップやステップの幅は経時的に増加することが観察されている. アマルガム修復物の辺縁破折のメカニズムについては, それがアマルガムの機械的特性, とくにクリープ値の大小に密接に関係すると言うMahlerらによるいわゆるRheological theoryとアマルガム修復物辺縁部の腐蝕に起因する窩壁からの剥離によるとするJφrgensenの吸水銀膨張説(Murcuroscopic expantion theory)とがある.
Practice　： 歯科学
Keywords　：

English

Title　： Study on the Fatigue Test of Dental Amalgam by Potential Drop Method
Subtitle　：
Authors　： Satoshi MIYAKUNI
Authors（kana）　：
Organization　： Department of Restorative Dentistry, Kanagawa Dental College
Journal　： Kanagawa Shigaku
Volume　： 16
Number　： 2
Page　： 157-171
Year/Month　： 1981 / 9
Article　： Original article
Publisher　： Kanagawa Odontological Society
Abstract　： The incident of marginal fracture is generally considered as a deficiency of amalgam, and the fatigue of marginal edge due to masticatory force is supposed to be one of a factor among those responsible for the fracture. A new device of the fatigue tester has been introduced in this study with a view to investigating the initiation and propagation of a fatigue crack generated within a material by repeated load. This testing method based upon the principle of the potential drop method has made it possible to detect the increase of electric potential arising in a specimen as a function of time or the number of repeated load. Furthermore, the electric potential value thus obtained can be converted to the fatigue crack length by means of the calculation formula derived from the experimental date. Four brands of amalgam alloys, two high copper alloys (SD and DA), conventional spherical alloy (HA) and conventional lathe cut alloy (LA), were used in the experriments. The prepared specimens with the dimentions of 2×3×25mm were divided into five groups by their age. Bending stress was applied to the specimens by using the fatigue tester and the values of electric potential were recorded up to the time when the number of repeated load indicated 1.4×10 5 and then these values were converted to the corresponding crack lengths. The compression test was also carried out with the specimens by standardizing their dimensions in accordance with ADA Specifications No.1, and the transverse loading measurement was determined at the same time with the specimens of the identical size with those used in the fatigue test. The obtained results were as follows : 1) It has been suggested that the application of the fatigue test by the potential drop method for dental materials is practicable. 2) The fomula applied to the conversion of the electric potential value to the crack length has been confirmed to be highly reliable. 3) By SEM observation of fractured amalgam specimens, the fatigue area demonstrated comparatively irregular texture, and a lot of micro-cracks could be observed around the core structure and within the matrix. 4) With regard to the crack length, the higher fatigue strength was shown by two high copper alloys as compared with the conventional alloys, and the ultimate strength was obtained at least twelve hours after the specimens were prepared. 5) As to the compressive and transverse strengths, one of the high copper alloys (DA) showed the value lower than those of the two conventional alloys, while it showed the highest value in the fatigue strength.
Practice　： Dentistry
Keywords　：