PURPOSE: To easily grind a cast body, by forming a small hole to the upper surface of the gypsum model of a crown and inserting a rod like article in the small hole so as to engage therewith before forming a wax pattern.

CONSTITUTION: A small hole 2 is formed to the upper surface of a tooth form 1 having the same shape as a tooth having to receive prosthesis dupplicated by gypsum and, after a rod-like article 4 having a head part 3 formed thereto is inserted in and engaged with said small hole 2 through an adaptor 19 wherein a circular flange 20 is formed to the upper end of a cylindrical body, wax 5 is built up on the upper surface of the tooth form 1 according to a usual method and the appearance thereof is arranged by a wax spatula. A spool pin 6 is thrust in the wax pattern 5 thus formed, and the wax pattern 5 and the rod like article 4 are detached from the tooth form 1 and casting is performed therefrom according to a usual method to obtain a cast body 7 having a projection 6 formed thereto. Subsequently, the adaptor 19 is detached and the obtained cast body is engaged with the small hole 2 of the tooth form 1 to perform the tooth form matching of the cast body. After the sprue 8 of the cast body 7 is cut off, the projection 6 is held by a holder to perform grinding finish. The projection 6 may be cut after the finish of grinding.