Introduction
A partial denture with precision attachments is really two prostheses made to fit each other exactly: fixed crowns carrying the matrices on the abutments, and a removable denture carrying the patrices. The technology is about keeping everything parallel and precise from the first cast to the final cementation.
Planning
- Study casts mounted in an articulator, surveyed to choose the path of insertion.
- Choice of abutments (often two splinted teeth on each side), the attachment type (rigid or resilient) and its position.
- Enough crown height and width for the attachment: measure before preparing.
Clinical and laboratory steps
- Tooth preparation for crowns, with extra reduction where an intracoronal matrix will sit.
- Impression and master cast with removable dies.
- Wax-up of the crowns; the plastic or metal matrix is placed with the surveyor (or a parallel mandrel) so that it follows the path of insertion. Splinted crowns are waxed together.
- Milling: guide planes, shoulders and reciprocal surfaces are milled in the wax or the casting, parallel to the path of insertion.
- Casting and fitting of the crowns on the dies; matrices soldered in if not cast-on.
- Try-in of the crowns and a pick-up impression: the crowns stay in the impression, and a new cast is poured with them in place.
- Framework: the cast denture framework is made on this cast, with the patrices cast in, soldered, laser-welded or bonded in.
- Try-in of the framework, jaw registration and setting of teeth in wax; try-in of the waxed denture.
- Processing of the acrylic base; finishing.
- Cementation of the crowns with the denture seated, so they line up; check occlusion.