Cast Gold

Implant manufacturers recognized the limitations of early “stock abutments” and developed a castable abutment called a UCLA abutment. This abutment is
comprised of a machined-fit gold alloy base that fits to the corresponding implant head, combined with aplastic sleeve which can be cut, modified, and added
to with wax prior to casting into gold .

Cast gold abutments were used to fabricate implant-level, custom-cast restorations that provided subgingival margins for esthetics, reduced height for vertical
occlusal clearance, and/or custom angles. Cast gold abutments were popular during 1980s and 1990s but with the introduction of more sophisticated stock
abutments and CAD/CAM milled abutments they have lost popularity.
 

• Gold specs: 60–65% gold, 20–25% palladium, 19%platinum, and 1% iridium (not a ceramic alloy).

• Melting range: Solid, 1400°C; liquid, 1490°C.

• Recommended casting alloys: High palladium or high noble porcelain fusing alloys or type III or type IV high noble dental alloys.

Generally, a plastic UCLA abutment is waxed up and customized to an ideal geometry and shape. After investing, the wax and plastic UCLA are burned out
of the pattern following the lost wax process.

When molten alloy is cast into the investment mold, the gold base component of the UCLA abutment is incorporated into the casting and provides a machined interface that precisely fits the implant.

The gold base is fabricated from a non-oxidizing alloy that promotes chemical adhesion of the cast alloy, but does not permit the adhesion of porcelain.