A Study of Cast-Soldering Method For Manufacturing Clasps

Abstract

The clasps, as retainers, are an essential component of removable partial denture and have various features dependent on the form of abutment tooth crown, on the relative position of teeth and of a tooth and its alveolar bone.These clasps has mostly been manufactured by casting method for cast clasps or soldering method for wire clasps. Yet recently a new technique of simplifying laboratory procedures was introduced for making combination clasps and attachments: a technique of casting metal onto the wire, and, in effect, the wire is soldered to the metal (Cast-Soldering Method hence).Studies of this Cast-Soldering Method, however, are comparatively fewer than those of microscopic observation of the microstructure and affinity of metals, and they need much to be studied.The present author analyzed the joint area of combination clasps made by Cast-Soldering Method with the help of Electron Probe X-ray Microanalyzer, and examined the changes in metal composition for the purpose of ascertaining the influence on the joint area, of different wire length and features of embedding in the casting mass, the kinds of investment material, and mold temperature. He obtained the following results.1. The factors that governed the tensile strength of 18k gold alloy by Cast-Soldering Method were the length and feature of embedding part, the kind of investment material, and mold temperature, with the interaction of investment material and mold temperature.2. The factors that governed the tensile strength of Au-Ag-Pd alloy were the length and feature of embedding part, the kind of investment material, and mold temperature, with the interaction of the length and feature of embedding part and mold temperature, of investment material and mold temperature, and the interaction among the length and feature of embedding part, investment material, and mold temperature.3. The tensile strength of the two kinds of alloy above examined increased, in the case of the length and feature of embedding: 4mm or L-featured embedding. The tensile strength also was found to increase, dependent on the kinds of investment material: Cristobalite and Real Vest; it also increased in inverse ratio with the mold temperature.4. The analyses by Electron Probe X-ray Microanalyzer proved that the tensile strength of the joint area depended on the degree of interlocking of the surface of wire and casting body (a part of joints revealed the fused condition and the diffusion of Pt was ascertained).5. The analyses by Electron Probe X-ray Microanalyzer indicated that the tensile strength decreased in proportion to the degree of fusion of the embedded dental gold (Pt-Au) wire, and when complete fusion was attained, the diffusion of Pt was distinctly observed.6. The analyses of Electron Probe X-ray Microanalyzer indicated that the extent of Pt diffusion increased in proportion to the mold temperature and the melting temperature.7. The above results indicates the necessity of cautions laboratory procedure because there exists more cases of interaction of factors in the application of Cast-Soldering Method to dental gold (Pt-Au) wire and Au-Ag-Pd alloy than to dental gold (Pt-Au) and 18K gold alloy.