Schiffleger B E, Ziebert G J, Dhuru V B, Brantley W A, Sigaroudi K
J Prosthet Dent. 1985 Dec;54(6):770-6. doi: 10.1016/0022-3913(85)90467-6.
An investigation was conducted to evaluate the accuracy of one-piece castings of FPDs consisting of three, four, and five units with a ceramometal alloy cast in a large circular ring. A three-piece aluminum mold with stainless steel dies simulating the various lengths of the FPDs was used. A total of 18 castings, six castings for each FPD, were fabricated. Marginal discrepancies of the castings on the dies and the length of the castings were compared before and after sectioning the castings at the connectors. The following conclusions were drawn from the study. Seating of the castings improved approximately 50% after sectioning, which indicates that the castings were distorted. The distortion was a three-dimensional phenomenon, with the greatest discrepancy on the mesiogingival surface of the anterior retainer and on the distolingual surface of the posterior retainer. The distortion was least for the three-unit FPDs and greatest for the five-unit FPDs. The lingual-facial diameter of the castings at the gingival axial line angle was significantly larger than the dies in most cases. The mesiodistal diameter of the castings at the gingival axial line angle was smaller than that of the dies but was only significant with the three-unit FPDs. Although the castings were slightly oversized or undersized, the primary reason the castings did not seat was warpage.
进行了一项研究，以评估在大型圆环中铸造的由三单位、四单位和五单位组成的烤瓷熔附金属全冠（FPD）一体式铸件的精度。使用了一个带有不锈钢模具的三件式铝制模具，该模具模拟了不同长度的FPD。总共制作了18个铸件，每种FPD有6个铸件。在铸件在连接体处切割前后，比较了铸件在模具上的边缘差异和铸件的长度。从该研究中得出了以下结论。切割后铸件的就位情况改善了约50%，这表明铸件发生了变形。这种变形是一种三维现象，在前牙固位体的近中牙龈表面和后牙固位体的远中舌侧表面差异最大。三单位FPD的变形最小，五单位FPD的变形最大。在大多数情况下，铸件在牙龈轴面角处的舌面-颊面直径明显大于模具。铸件在牙龈轴面角处的近远中直径小于模具，但仅在三单位FPD中差异显著。尽管铸件略有过大或过小，但铸件不能就位的主要原因是翘曲。
