A technique for developing a master cast with previously made dies

This article describes a technique for preparing final working casts to be used in the laboratory phase of restorative treatment. The goal is to produce accurate working casts that have stable dies which are easily removed from the base and reliably replaced. Most casts with removable dies are made from a single master impression. However, individual dies are sometimes made previously from individual tooth (preparation) impressions. In such cases, transfer copings are required to relate the dies and produce the final working cast. Hollow plastic casting sprues are used as temporary dowels in this technique until a transfer coping pickup impression has been made. After the dies are seated and secured in the transfer coping pickup impression, the plastic casting sprues are replaced with conventional brass dowel pins. This technique ensures well-placed dowel pins that will facilitate easy and accurate withdrawal and replacement of the dies.