Walters R A, Spurrier S
Department of Removable Prosthodontics, University of Maryland Dental School, Baltimore, Md.
J Prosthet Dent. 1990 Mar;63(3):277-81. doi: 10.1016/0022-3913(90)90194-h.
One-unit fixed partial dentures, which fit accurately on the laboratory dies made from polysulfide impression materials, often pose a problem in seating completely in the mouth of the patient. Sectioning of the fixed partial denture units allows the individual units to seat accurately in the mouth but requires a soldering procedure. Linear distortion of the mercaptan (polysulfide) rubber base that takes place during setting is a cause of this problem. The distortion is directly related to (1) tray design, (2) area of adhesive placement, and (3) excessive bulk of material on the tray border during impression making. A controlled amount of adhesive and impression material in a new design for a custom tray must be used to minimize this distortion. When these factors are controlled, the resulting impression is unrestricted, and a more accurate working die is obtained. This results in a better fit of one-unit fixed partial dentures in the mouth.
单单位固定局部义齿在由聚硫橡胶印模材料制成的实验室模型上精确适配，但在患者口腔中完全就位时常常出现问题。将固定局部义齿部件进行分割可使单个部件在口腔中精确就位，但这需要焊接操作。在凝固过程中硫醇（聚硫橡胶）橡胶基托发生的线性变形是导致此问题的一个原因。这种变形与以下因素直接相关：（1）托盘设计；（2）粘结剂放置区域；（3）印模制取过程中托盘边缘材料堆积过多。在定制托盘的新设计中，必须使用可控量的粘结剂和印模材料，以尽量减少这种变形。当这些因素得到控制时，所获得的印模不受限制，并且可以得到更精确的工作模型。这使得单单位固定局部义齿在口腔中的适配性更好。
