EXPERIMENTAL IMPRESSION TRAY FABRICATED WITH Ni-Ti SHAPE MEMORY ALLOY

我们经常会遇到由于印模材料的弹性，当一个石头模型从印模中取出模型断裂。如果使用形状记忆合金作为托盘材料，我们认为，石模型可能能够很容易地从印模托盘中取出，而模型不会断裂。本文介绍了日本古河电机公司研制的一种镍钛形状记忆合金板，并利用该合金板制作了一个小型实验印模托盘。实验用形状记忆合金制成的托盘为30×30× 15 mm的盒形，托盘厚度为0.67mm。（石制模型从印模中拔出试验）取模时使用下颌牙科研究模型（D15 FE-500 A，日清）。将硅胶印模材料（Exafine，GC）注射到具有四颗后牙的模型周围，然后定位托盘。材料凝固后，将一定重量的石头（New Fujirock，GC）浇铸到印模中。恢复前的拔出力 关于我们 形状记忆为23.5（4.0）N，并且显示出与市售托盘23.5（2.0）N的等效值。然而，在形状记忆恢复之后，获得的力为15.7（2.0）N。（托盘形状记忆效应的耐久性）托盘在70℃下恢复后，每次都必须用手校正托盘，宽度最多为20 mm。初始恢复宽度为30 mm，100次循环后为24 mm，5，000次循环后为23.1 mm。但是，通过热处理的形状记忆效应，托盘恢复到初始宽度。此外，将托盘在高压灭菌器中加热至132℃持续20 min以模拟灭菌过程，然后进行所述的回收程序。在100次加热循环后，恢复能力没有变化。（将石模从印模中拔出所需的力）使用三种有多颗缺失牙齿的研究模型制作印模。比较了记忆成型托盘与传统托盘取石的难易程度。实验结果表明，从实验托盘上取石模型比从传统托盘上取石模型容易。常规托盘组有3个标本发生断裂，而实验托盘组无一例发生断裂。从上述事实来看，形状记忆托盘似乎可用于临床使用。少

We often experience a model fracture due to the elasticity of impression materials, when a stone model is removed from the impression. If a shape memory alloy is used for tray material, we considered, stone model might be able to easily remove from the impression tray without model fracture. A Ni-Ti shape memory alloy plate was developed by Furukawa electric Co. and we used this alloy plate to fabricate a small experimental impression tray. This experimental tray made of the shape memory alloy was fabricated in a box shape of 30×30×15mm and the thickness of tray was 0.67mm.(Pull-out test of the stone model from the impression)The mandible dental study model (D15FE-500A, Nissin) was used for an impression taking. The silicone impression material (Exafine, GC) was injected around the model with four posterior teeth and the tray was then positioned. After setting the material, a definite weight of stone (New Fujirock, GC) was cast into the impression. The pull-out force before recovery of … More the shape memory was 23.5 (4.0) N and showed an equivalent value to the commercially available tray of 23.5 (2.0) N.However after recovery of the shape memory, the force obtained was 15.7 (2.0) N.(Durability of the shape memory effect of the tray)After the tray was recovered at 70℃, the tray had to be corrected by up to 20mm in width by hand each time. The width by recovery was 30mm at initial, 24mm after 100 cycles and 23.1mm after 5,000 cycles. However, by the heat treatment for shape memory effect, the tray recovered to the initial width. In addition, the tray was heated to 132℃ for 20 min in autoclave to simulate sterilization process, then the oreviously descrived recovery procedure was conducted. There was no change in the ability of recovery after 100 cycles of heating.(Force required for pull-out the stone model from the impression)Impressions were made using three kinds of study models that had several missing teeth. The easiness for removing stone models was compared between memory shaped tray and conventional tray. Specimens were made according to common impression taking and gypsum pouring, As the result, removal of the stone model from the experimental tray was easier than that from the conventional tray. Three specimens were fractured in the group of conventional tray, contrary there was no fractured specimens in the group of experimental tray. From the above fact, the shape memory tray seems to be useful for clinical use. Less