EXPERIMENTAL IMPRESSION TRAY FABRICATED WITH Ni-Ti SHAPE MEMORY ALLOY

我们经常会遇到由于压模材料的弹性导致的模型断裂，当一个石头模型从压模中取出时。如果使用形状记忆合金作为托盘材料，我们认为，石头模型可以很容易地从印模托盘中取出，而不会造成模型断裂。一种镍钛形状记忆合金板是由古川电气公司研制的，我们用这种合金板制作了一个小型的实验印痕盘。该实验用形状记忆合金制作成盒子形状30×30×15mm，托盘厚度为0.67mm。（从印模中拔出石模型试验）采用下颌骨研究模型（D15FE-500A，日清）取印模。将硅胶印模材料（Exafine， GC）注射到四颗后牙的模型周围，然后定位托盘。在确定材料后，一定重量的石头（新藤岩，GC）被铸造到印版中。形状记忆恢复前的拉拔力为23.5 (4.0)N，与市买托盘的23.5 (2.0)N相当，而形状记忆恢复后的拉拔力为15.7 (2.0)N。（托盘形状记忆效应的耐久性）在70℃下恢复后，每次需要手工修正的托盘宽度最多为20mm。初始回收宽度为30mm，循环100次回收宽度为24mm，循环5000次回收宽度为23.1mm。然而，由于形状记忆效应的热处理，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℃20 min，模拟灭菌过程，然后进行上述回收程序。加热100次后，其恢复能力没有变化。（从印模中拔出石头模型所需的力）印模是用三种缺失了几颗牙齿的研究模型制作的。比较了记忆型托盘与常规托盘的移石便利性。采用常规的取模法和石膏浇筑法制作标本，结果表明，从实验托盘中取出石头模型比从常规托盘中取出石头模型更容易。常规托盘组有3例试件断裂，而实验托盘组无试件断裂。从以上事实来看，形状记忆托盘在临床应用中似乎是有用的。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