Kato H
Aichi Gakuin Daigaku Shigakkai Shi. 1989 Dec;27(4):1017-27.
Usually the mechanical properties of dental alloys are determined from the values obtained through static tests of their tensile strength, hardness, etc. Generally, high tensile strength and ductility are preferred. However, when small stresses within proportional limits are applied repeatedly (even though not amounting to destructive forces in static tests), they may cause rupture in the alloy or, at least, cause it to lose its original mechanical properties. This phenomenon is called metal fatigue. It is estimated that the intraoral stress loads received by dental restorations during mastication or during insertion and removal of appliances are repeated more than 3 x 10(5) times/year. From this standpoint, it may be more appropriate to estimate the fracture strength of such dental alloys based on the fatigue properties of the restorative materials used for clasps, bars, and fixed bridges. For this reason, it is necessary to obtain data through fatigue tests on the fatigue strength and the fatigue endurance limits of dental alloys, and it is important to find a correlation between these data and the static data on tensile strengths and ductility obtained by tensile tests. Two alloys are used in these experiments. Both wrought specimens and cast specimens of 12% Au-Pd-Ag and Type III gold alloy were prepared for the fatigue tests. The size of the rectangular wrought specimens was 3 x 4 x 110 mm. The 12% Au-Pd-Ag alloy was heated to 800 degrees C for 15 minutes, quenched, and reheated to 400 degrees C for 20 minutes and quenched again according to the manufacturer's instructions for heat treatment. The Type III gold alloy was heated to 700 degrees C for 10 minutes, quenched, and reheated to 350 degrees C for 20 minutes and quenched again. The cylindrical cast specimens were 60 mm long and 2 mm in diameter. They were invested by conventional methods and cast in a centrifugal casting machine, Thermotrol Model 2500. The four point bending test for the wrought specimen was performed with a Universal Fatigue testing machine, Shimazu UF-15 at a stress amplitude rate of 30 Hz. The cylindrical cast specimens were tested in cyclic tension in a Hydraulic IC Servo Machine, Instron Model 8501 at a gauge length of 25 mm and a stress amplitude of 10 Hz. The tensile tests for both wrought and cast specimens were performed with a Universal Testing Machine, Instron Model 1125 and measured at a cross-head speed of 1 mm/min.(ABSTRACT TRUNCATED AT 400 WORDS)
通常，牙科合金的机械性能是通过对其拉伸强度、硬度等进行静态测试所获得的值来确定的。一般来说，较高的拉伸强度和延展性是比较理想的。然而，当在比例极限内反复施加小应力时（即使在静态测试中这些应力并不构成破坏力），它们可能会导致合金破裂，或者至少使其失去原有的机械性能。这种现象称为金属疲劳。据估计，牙科修复体在咀嚼过程中或在佩戴和取下矫治器时所承受的口腔内应力负荷每年会反复超过3×10⁵次。从这个角度来看，基于用于卡环、杆和固定桥的修复材料的疲劳性能来估计此类牙科合金的断裂强度可能更为合适。因此，有必要通过对牙科合金的疲劳强度和疲劳耐力极限进行疲劳测试来获取数据，并且找到这些数据与通过拉伸试验获得的拉伸强度和延展性的静态数据之间的相关性很重要。在这些实验中使用了两种合金。制备了12% Au-Pd-Ag合金和III型金合金的锻造试样和铸造试样用于疲劳测试。矩形锻造试样的尺寸为3×4×110毫米。按照制造商的热处理说明，将12% Au-Pd-Ag合金加热至800℃ 15分钟，淬火，然后再加热至400℃ 20分钟并再次淬火。将III型金合金加热至700℃ 10分钟，淬火，然后再加热至350℃ 20分钟并再次淬火。圆柱形铸造试样长60毫米，直径2毫米。它们采用常规方法包埋，并在Thermotrol 2500型离心铸造机中铸造。锻造试样的四点弯曲试验在岛津UF-15型万能疲劳试验机上以30赫兹的应力振幅速率进行。圆柱形铸造试样在Instron 8501型液压IC伺服机中进行循环拉伸试验，标距长度为25毫米，应力振幅为10赫兹。锻造和铸造试样的拉伸试验均在Instron 1125型万能试验机上进行，以1毫米/分钟的十字头速度测量。（摘要截选至400字）
