Lost-Wax Technique — MFDS Part 1 MCQ
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Correct answer: E — Create the wax pattern → sprue and invest it → burn out the wax → cast the alloy → divest and finish
Option E is correct. The restoration is first reproduced as a wax pattern. A sprue is attached, and the pattern is surrounded by refractory investment. Heating then eliminates the wax, leaving a mould cavity corresponding to the pattern. Molten alloy is cast into this cavity; after solidification, the investment is removed, the sprue is cut off and the casting is finished. In B, the unsupported pattern is burnt out before investing. In C, spruing is attempted after the pattern has been enclosed in investment. In D, casting precedes wax elimination, so there is no empty mould cavity. In E, divesting before casting destroys the mould required to receive the alloy.
Reference: Salyer KE, Johns DF, Holmes RE, Layton JG. Evolution of the mandibular mesh implant—lost-wax fabrication description. Journal of Biomedical Materials Research. 1977;11(4):461–470. https://pubmed.ncbi.nlm.nih.gov/39944861/