Explain the procedure for the “altered/modified cast technique”.

Explain the procedure for the “altered/modified cast technique”.

1. Altered cast technique is a method of distributing the load suitability between abutment teeth and the edentulous ridge is by muco-static impression techniques for the standing teeth combined with muco-compressive impression techniques for the edentulous ridges.

2. The working impression is taken 'normally' by the clinician using alginate or silicone material. This will reproduce the edentulous ridges in a relatively muco-static condition. If the mucosa is displaceable, a finished denture constructed on a model from this impression will move under functional loading as the mucosal tissue compresses under loading.

3. The cast metal framework is constructed to a working model poured from this alginate or silicone impression and sent to the surgery for a try-in.

4. If the try-in of the metal framework is satisfactory it is returned to the technician to add self-cure acrylic denture bearing areas to the denture bearing area framework, thus forming a tray' for the impression (usually constructed from auto-polymerising or light cured materials).

5. The clinician then uses Special impression Waxes (such as Kerr's Korrecta wax No.4.) to record the edentulous ridges under function, exercising care in ensuring that the metal framework is seated firmly around the tooth supporting areas. This provides a record of the mucosa in a compressed state, where the underlying hard tissue areas become obvious.

6. When this is received in the laboratory technician cuts away the edentulous areas of the original model and the metal framework if re-seated accurately. The new wax impression is then poured in stone to form this modified or altered cast/model. The denture base can now be processed and will correspond to the edentulous areas in function.