Introduction
Modern laboratory systems standardize bridge-making so that copings have even walls, cement space is built in, and the whole framework is cast in one piece. Students learn the "Adapta" system (deep-drawn foil copings), combined with prefabricated wax sprues and ringless casting.
Before the laboratory
- Diagnostic casts, mounted with a facebow on a semi-adjustable articulator with check bites, show the space, the occlusion and the path of insertion.
- Abutments are prepared parallel to each other; a precise impression and a cast with removable dies are made (topic 32).
The Adapta foil coping
Two polypropylene discs are used together: a 0.6 mm carrier (base) foil and a 0.1 mm spacer foil on top. Drawing roughly halves their thickness.
- Place both foils in the holder, spacer on top.
- Heat evenly and slowly over the flame until the foils turn transparent and soft.
- Press the die into the silicone moulding material through the foils; hold about 10 seconds until cool.
- Open the holder, pull die and foils out of the mould, cut the foil, and remove the coping from the die.
- Trim the coping about 1 mm short of the finish line, and the spacer shorter still (by about a third of the coping height).
- Seat the spacer on the separated die, then the coping over it; fill the margin with cervical wax.
Overheated foil gives copings that are too thin; underheated foil gives thick, distorted ones.