Heath J R, Boru T K, Grant A A
Department of Restorative Dentistry, Dental School, University of Manchester, U.K.
J Oral Rehabil. 1993 Jul;20(4):363-72. doi: 10.1111/j.1365-2842.1993.tb01619.x.
The bases of occlusal rims and trial dentures should fit both the cast and the mouth accurately. The retention of shape and dimension of strips and sheets of grey and pink shellac, filled cold cure acrylic resin and wax were tested following moulding over stylised upper edentulous casts. The thermoplastic materials were softened over a flame or in a water bath. Specimens were prepared with and without folding along the long axes of the strips. The angles formed by the strips, the gap between the palate of the baseplates and casts and the linear dimension of the sheets were measured after moulding, after immersion in water at 37 and 45 degrees C and after 24 h at room temperature. The least angular change was shown by unfolded grey shellac, softened over a flame and moulded by finger pressure over an unwarmed cast, followed by folded specimens softened in water and moulded with the fingers over a prewarmed cast. The least gap developed beneath pink shellac softened in water and moulded by finger pressure over a warmed cast. The smallest dimensional change was shown by grey shellac softened in water and moulded by finger pressure over a warmed cast. Thus, optimally manipulated shellac materials exhibit less change after moulding than cold cure acrylic resin or modelling wax.
咬合堤和试戴义齿的基托应精确贴合模型和口腔。在标准化的上颌无牙颌模型上塑形后，对灰色和粉色虫胶条与片材、填充型冷固化丙烯酸树脂及蜡的形状和尺寸保持情况进行了测试。热塑性材料在火焰上或水浴中软化。制备了沿条带长轴折叠和未折叠的试样。在塑形后、浸入37℃和45℃水中后以及在室温下放置24小时后，测量条带形成的角度、基托腭部与模型之间的间隙以及片材的线性尺寸。角度变化最小的是在火焰上软化、通过手指压力在未预热模型上塑形的未折叠灰色虫胶，其次是在水中软化、通过手指压力在预热模型上塑形的折叠试样。在水中软化、通过手指压力在预热模型上塑形的粉色虫胶下方形成的间隙最小。尺寸变化最小的是在水中软化、通过手指压力在预热模型上塑形的灰色虫胶。因此，经过最佳操作的虫胶材料在塑形后比冷固化丙烯酸树脂或造型蜡表现出更小的变化。
