Post-soldering of nonprecious alloys

Marginal fit of metal ceramic restorations subjected to a standardized postsoldering technique

The fit of a fixed partial denture (FPD) is fundamental for the clinical success of a restoration. When a postsoldering procedure is needed, a high-precision laboratory technique is necessary to not affect the fit of the FPD. This article evaluates whether a standardized postsoldering technique affected the marginal fit of a 3-unit high palladium alloy FPD. One hundred and eight measurements were made of 3-unit FPDs, fabricated in a high palladium alloy (2% Au-79% Pd-10% Cu-8% Ga) and constructed on 9 tin dies in vitro. After the castings were fabricated, specimens were measured at 3 specific points per abutment (distal, labial, lingual) before and after soldering. Differences were found in the marginal opening of both copings, before soldering (49.9 microm) and after soldering (48. 3 microm). There was no significant difference in the adaptation of the copings after the soldering procedure (P<.05).

Mechanical properties of metal connectors soldered by gas torch versus an infrared technique

PURPOSE

The ultimate tensile strength and percentage elongation of solder joints of three alloy systems were tested.

MATERIALS AND METHODS

Solder joints were formed using either an infrared soldering machine or gas-oxygen torch. Intact solder materials were used as controls.

RESULTS

There were no significant differences in percentage elongation among different treatment methods of the solders or among various solder materials. All intact solder materials possessed significantly higher ultimate tensile strength than the joints made with either method. For high-noble and noble alloy solders, there were no significant differences in ultimate tensile strength of joints made with either method. For base metal alloy solder, the ultimate tensile strength of joints made with the infrared technique was significantly higher than that made with the gas-oxygen torch technique.

CONCLUSIONS

The infrared technique can be used as an alternative to the gas-torch technique for soldering high-noble and noble alloys. It is superior to the gas-torch technique for soldering a cobalt-chromium alloy.

The fit of fixed partial dentures joined by infrared soldering

This study determined the accuracy of fit of three-unit fixed partial dentures joined by an infrared soldering technique compared with one-piece fixed partial denture castings and individually cast crowns. Wax patterns of prepared Ivorine teeth, maxillary left central incisor and maxillary left canine, were injection molded; a plastic rod was used as a pontic. One group of patterns was cast as one-piece dentures; the other group was sectioned in the connector area, cast individually and then joined by infrared soldering. Castings were seated on their respective dies, embedded in epoxy resin, and sectioned. Gap distances between the casting and the die were measured at specified marginal sites with a profile projector. Results showed that the fit of infrared-soldered fixed partial dentures was significantly better than that of one-piece castings and was comparable with the fit of single crowns. The gap openings measured in all castings were within the range of clinical acceptability.

Soldering nonnoble alloys

Successful presoldering of nonnoble alloys is variable at best. Under controlled conditions of joint gap distance, investing, and soldering, more than one third of the soldered joints are likely to fail. Furthermore, the recorded strength of successful solder joints was inconsistent. Improved heat application and controlled oxidation are required. Until new materials and/or techniques are developed, the soldering of nonnoble alloys prior to the application of porcelain is unwarranted.