Open-cast technique for metal molds used in constructing facial prostheses

Our plain-English summary of Open-cast technique for metal molds used in constructing facial prostheses, by O.N. Guerra, K. Canada (The Journal of Prosthetic Dentistry, 1976).

The study

• Authors: O.N. Guerra, K. Canada
• Journal: The Journal of Prosthetic Dentistry
• Published: 1976;36(4):421-5
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A new (open-cast) technique for the fabrication of metal molds has been presented. Its simplicity relies on the use of gummed asbestos tape as a boxing agent for the investment models. This technique has the following advantages over the "lost wax" technique: (1) it requires approximately one-quarter the amount of investment material, (2) it eliminates the use of investing rings or wax patterns, (3) it eliminates the boil-out step for the wax pattern and reduces the total time required to make a metal mold, and (4) it affords a high degree of visibility. The only disadvantage is that the larger prostheses require large amounts of Lino-type metal which is very heavy. However, this has not restricted the use of this technique since these metals cast well and can be easily placed in large ovens. This technique, because of its advantages, offers more efficient use of laboratory time and personnel.

In plain English

This 1976 article was a laboratory technique description, not a health study. The authors described an 'open-cast' method for making metal (Linotype) molds for facial prostheses, using a nasal prosthesis as the example. Gummed asbestos tape, available at a hardware store, was moistened in water and wrapped in five layers around an investment model to form a box. The boxed model was dried overnight in an oven at 150 C, heated to 190 C, and then filled with molten metal. After cooling, the tape was described as readily removed. Compared with the 'lost wax' method, the authors said their technique needed about one-quarter the investment material, eliminated wax patterns and investing rings, saved time and gave a high degree of visibility. The article reported no measurements behind these comparisons. The only disadvantage named was the heavy metal needed for larger prostheses. The authors concluded the technique offered more efficient use of laboratory time and personnel. The article did not discuss health effects, dust, or the fiber type of the tape.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Description of a dental laboratory technique (method for fabricating metal molds); not a health or exposure study
• Who was studied: No people were studied. The article describes making metal molds for facial prostheses, using a nasal prosthesis as the worked example, at Ellis Fischel State Cancer Hospital and Cancer Research Center, Columbia, Missouri.
• Exposure: Gummed asbestos tape (3 inch width) used as a boxing material around investment models. It was moistened in water, wrapped in a first layer plus four additional layers, dried in an oven (150 C overnight, then 190 C), and removed after the metal was cast. No fiber type and no exposure measurements were given.
• Main results:
  • The moistened tape was wrapped around the investment cast in a first layer ending in a butt joint, followed by four additional layers.
  • The boxed investment models were dried in a dry-heat oven at 150 C overnight. The oven was raised to 190 C two hours before casting.
  • After the metal had cooled and been plunged into water, the asbestos tape was described as readily removed.
  • The authors stated that, compared with the lost wax technique, the open-cast technique requires approximately one-quarter the amount of investment material, eliminates investing rings, wax patterns and the boil-out step, reduces total time, and affords a high degree of visibility. No measured data were reported.
• The authors' conclusion: The authors concluded that, because of its advantages, the technique offers more efficient use of laboratory time and personnel.
• Limitations the authors state:
  • The authors stated that the only disadvantage is that larger prostheses require large amounts of Linotype metal, which is very heavy.

Related studies

• Metal interactions in carcinogenesis: enhancement, inhibition — G.F. Nordberg, O. Andersen (1981)
• Occurrence of heavy metal-resistance in microflora from serpentine soil of Andaman — A. Pal, S. Dutta, et al. (2005)
• Impact of effects of acid precipitation on toxicity of metals — G.F. Nordberg, R.A. Goyer, et al. (1985)
• Occupational exposure to dyes, metals, polycyclic aromatic hydrocarbons and other agents and K-ras activation in human exocrine pancreatic cancer — J. Alguacil, M. Porta, et al. (2003)
• Biodurability and release of metals during the dissolution of chrysotile, crocidolite and fibrous erionite — A.F. Gualtieri, G. Lusvardi, et al. (2019)
• Occupational dermatoses and allergy to metals in Polish construction workers manufacturing prefabricated building units — M. Kieć-Swierczyńska (1990)

Browse more research in The Journal of Prosthetic Dentistry, or return to medical research.