RPD Manual 11 - Removable Prosthodontics - Dalhousie University

Jaw Relations, Altered Cast Technique and Wax Try-in - 89
Maxillo-Mandibular Relations, Altered Cast Impressions and Wax Try-in Procedures
Once a removable partial denture framework has been properly adjusted, teeth must be placed on
a framework to check the esthetics, phonetics and function. To set denture replacement teeth,
the casts must be mounted on an articulator.
For tooth-borne partial dentures with small edentulous areas, a wax denture base can be placed
directly on the denture framework. One thickness of baseplate wax is adapted over the
edentulous area, the framework is heated sufficiently to melt the wax, and the framework is fully
seated onto the cast, so that the wax melts and attaches to it. For more extensive tooth borne
partial dentures, and tooth-tissue partial dentures, an acrylic base (without wax spacer) is
attached, for greater stability. Wax occlusion rims are added to the wax or acrylic base and
maxillo-mandibular relation records are obtained for the purposes of mounting the casts on an
articulator. The steps in this procedure are as follows:
1. Make a face-bow (earbow) transfer and have it checked by an instructor prior to removal
from the patient. Wax is softened, placed on the face-bow bitefork and while the wax is
still softened, placed intraorally with minimal pressure (to minimize possible tooth
movement). The posterior-most teeth MUST BE CAPTURED IN THE WAX RECORD
so that the maxillary cast is stable once placed in the record.
Stable Unstable
If the cast tends to unseat from the registration (e.g. due to weight of cast, angulation of
face-bow etc.) it should be stabilized with sticky wax or elastic bands. Prior to mounting
of the cast, three 'V' or ‘U’-shaped notches, with no undercuts should be placed in the base
of the cast (similar to those placed for complete dentures). The maxillary cast is mounted
in a two-step method. Initially the base of the cast is dampened and a small mound of fast
set plaster is placed so that it locks onto the mounting ring and covers a small area of the
upper cast surface. The plaster should not extend past the cast periphery in any area. The
plaster is allowed to set (