Grant-in-Aid for Scientific Research (B).
|Research Institution||TSURUMI UNIV.SCHOOL OF DENTAL MEDICIN|
KOHNO Atsushi TSURUMI UNIV., DENTISTRY, PROFESSOR, 歯学部, 教授 (00064345)
岩井 博久 古河電工(株)・古河テクノマテリアル
IKEJIMA Iwao TSURUMI UNIV., DENTISTRY, ASSISTANT, 歯学部, 助手 (50222865)
OZAWA Masaaki TSURUMI UNIV., DENTISTRY, ASSISTANT, 歯学部, 助手 (00204199)
HIRANO Susumu TSURUMI UNIV., DENTISTRY, PROFESSOR, 歯学部, 教授 (00089400)
IWAI Hirohisa FURUKAWA TECHNO MATERIAL Co.
|Project Fiscal Year
1998 – 2000
Completed(Fiscal Year 2000)
|Budget Amount *help
¥6,300,000 (Direct Cost : ¥6,300,000)
Fiscal Year 2000 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1999 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Fiscal Year 1998 : ¥3,100,000 (Direct Cost : ¥3,100,000)
|Keywords||IMPRESSION TRAY / SHAPE MEMORY ALLOY / NI-TI ALLOY / 形状記憶合金 / NiTi合金 / 印象用トレー / 形状記憶合金板|
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 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.