Partials

Q: When casting a full palate with 3/10" thick stippled pattern, is it possible for the investment to expand and stop the alloy from fully casting?

A: In theory, if the mold were heated to an extremely high temperature, the expansion could cause the top of the mold cavity to touch the bottom. However, if the investment were to survive, the casting would be useless because over-expansion would make the fit unacceptable.

If you're having trouble casting a full base, the real problem is probably the spruing technique. The most common mistake technicians make when casting full bases is trimming the refractory cast so that the posterior ridges are parallel to the base. Instead, the cast should be trimmed so that the posterior ridges form at least a 30-degree angle to the base. This allows the molten alloy to enter the mold cavity in a smooth flow rather than at a 90-degree angle which causes a great deal of turbulence. Turbulence causes a breakdown of the refractory cast,...