7- Preparing Example Cast, Master Cast & Work Authorization

What is an example cast

A “final” impression that was not good enough to use for master mast. Minor defects can be acceptable for example cast fabrication

What stone should you use for pouring up the example cast

White stone or type IV if you are pouring two equally good impressions, one will be master and one will be example

What should be included on the example cast?

All elements of framework drawn, correct proportions and location in color-coding used for chrome and wrought wire. It must be surveyed, HOC, include the outline of acrylic resin base, outline rests and clasps

What is the point of the example cast?

To help doc and lab tech visualize relationship of RPD elements to teeth and soft tissues

Why are the drawings not done on the master cast?

Because lines would complicate the lab tech’s preparation of the master cast for duplication (they have to duplicate it for the refractory cast)

Why do you need to tripod the master cast?

To allow the technician to orient the master cast on their survey table to doc’s selected POI

What should you use to tripod the master cast?

0.030 undercut gauge; should be widely separated on palatal and lingual areas of maxillary and mandibular casts.

Which copy of the work authorization does the lab get

White (original)

Which copy of the work authorization does the patient’s chart get

Yellow

For RPD/RPD cases, it may be helpful to use two forms to avoid confusion

Why do you need to include these instructions for maxillary RPD: Do not bead or place any post dams

We place our own beading and do not delegate it

Why do you need to include these instructions for mandibular RPD: Place one layer of wax over exposed root surface

Only used if a lingual plate lies over exposed roots

Why is Lucitone 199 used

For greater strength and translucency

What other material could be used to better match gingival shade in patient if necessary?

Lucitone Characterized light reddish-pink, Brunet

What 3 things are given to the lab for RPD framework construction

1. Work authorization

2. Drawn on example cast

3. Tripoded master cast