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Overdenture System
Male on the post-coping
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| The threaded base ring is either cast-to or soldered to the
post and coping. The precision female is fixed in the acrylic resin either in the
laboratory, or by the dentist. Advantage:
- Reduced chance of food impaction in the attachment
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Fabrication of the post coping:
Cast To Technique
| Wax up the post-coping as low as possible (FIG
1). Use the
(RE) P4 paralleling mandrel for the castable base ring.
Thread the paralleling mandrel into the base ring (FIG
2). The occlusal
surface must be at an angle of 90 degrees to the path of insertion (FIG
3). |
| Completely surround the base ring with wax (FIG
4). Make sure
that the wax pattern ends only a few tenths of a mm below the upper metal ledge to prevent
metal from flowing in (FIG
5). Paint
liquid colloidal
graphite (available
from Preat Corporation), or anti flux, on the threads of the base ring to prevent any cast metal from
adhering. Allow the graphite to totally dry
before investing. A two stage investing process is recommended. Allow
the initial investment to set for 30 minutes (FIG
6). |
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Tips:
- Paint an anti-flux such as Colloidal Graphite on the
threads to prevent flash from adhering to the threads. Let the Colloidal Graphite
fully dry before casting.
- Slowly flow investment into the
threads of the base ring.
Do NOT sandblast
to remove investment.
- Cut a small slot in the wax surrounding the base
ring with a fine instrument to prevent metal from flowing into the base
ring (FIG X).
The base ring may only be cast with precious or
semi-precious alloys for the coping. |
FIG X |
7 |
8 |
| In cases of limited space, the post coping may also be waxed
up in a concave form (FIG 7). The rounded shape of the coping provides for easy patient
cleaning and hygiene maintenance (FIG
8). |
The next step: Retaining the female in the
prosthesis
T0033.REV.00
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