Patent ID: 7325585
Filing Date: 2008-02-05
Classification: B22C

Abstract:
1. A method of forming a dental prosthetic by direct casting, said method comprising the steps of: forming a unitary cavity in a mold of investment, said unitary cavity incorporating a dental prosthetic pattern cavity portion, a double-ended elongated reservoir cavity portion and at least one sprue leading from said elongated reservoir cavity portion to said dental prosthetic pattern cavity portion, said unitary cavity being wholly disposed within said investment, and said mold of investment defining a substantially straight passageway substantially orthogonally disposed relative to said elongated reservoir cavity portion directly leading from the elongated reservoir cavity portion from a location between the ends thereof to the exterior of said mold investment, said unitary cavity being completely surrounded by said investment except at said substantially straight passageway; introducing an amount of molten casting alloy into said elongated reservoir cavity portion through said substantially straight passageway directly to said elongated reservoir cavity portion; causing said molten casting alloy introduced into said elongated reservoir cavity portion to flow from said elongated reservoir cavity portion through said at least one sprue into said dental prosthetic pattern cavity portion, the amount of molten casting alloy introduced into said elongated reservoir cavity portion being sufficient to completely fill said dental prosthetic pattern cavity portion and said at least one sprue and partially fill said elongated reservoir cavity portion whereby a sufficient amount of molten casting alloy will be contained in said elongated reservoir cavity portion within the confines of said investment to be drawn into said dental prosthetic pattern cavity portion through said at least one sprue due to cooling of said molten casting alloy in said dental prosthetic pattern cavity, and said amount of molten casting alloy introduced into said elongated reservoir cavity portion being insufficient to completely fill said elongated reservoir cavity portion after said molten casting alloy fills said dental prosthetic pattern cavity portion and said at least one sprue whereby said molten casting alloy remaining in said elongated reservoir cavity portion during drawing of the molten casting alloy into the prosthetic pattern cavity portion does not reach said substantially straight passageway and will not be drawn into said substantially straight passageway upon cooling of said molten casting alloy; and employing said investment to insulate and delay cooling of said molten casting alloy in said elongated reservoir cavity portion to promote replenishment of the molten casting alloy in the dental prosthetic pattern cavity portion and at least one sprue from molten casting alloy solely from said elongated reservoir cavity portion to produce a well defined, accurate dental prosthetic substantially free of internal voids.