working cast
The accurately poured stone or plaster model of a patient's prepared teeth upon which a laboratory technician directly fabricates a prosthetic restoration.
Full Definition
A working cast (also called a master cast or working model) is the primary stone replica of the patient's dental arch produced from a clinical impression, upon which all direct laboratory fabrication—die preparation, wax-up, framework fitting, and porcelain build-up—is performed. It must exhibit maximum dimensional accuracy and surface detail to ensure the resultant prosthesis will fit the patient's prepared teeth. Type III or Type IV dental stones are typically used, with higher-strength stones reserved for crown-and-bridge work where die trimming is required. In implant cases, the working cast incorporates implant analogs. Editors should distinguish 'working cast' from 'opposing cast' (the unprepared arch model) and 'refractory cast' (a heat-tolerant copy used in ceramic firing), as these are distinct items on laboratory work orders.
Usage
Usage note: Distinguish clearly from 'opposing cast' (the non-prepared arch) and 'diagnostic cast' (used for treatment planning, not direct fabrication). In crown-and-bridge work, the working cast often contains individual removable dies.
In Context
- "The working cast was trimmed and articulated with the opposing cast before the bridge framework try-in." — Laboratory work order
- "Air bubbles on the working cast margin were flagged by the technician prior to commencing the wax pattern." — Quality control log