12. Preparing the Master Cast Flashcards
Fitting Cast
The cleaned and ready master casts should be ____ before anything is drawn on them. This gives you a cast to fit the framework to after it is fabricated. You don’t want to abrade the master cast, even after fabrication.
duplicated
Design Transfer
The ____ and well designed diagnostic casts should accompany the ____ to the laboratory along with your prescription so that the ____ portion of the design will be accurately transferred to the final framework.
clean
master casts
metallic
Design Transfer Master casts critical elements: \_\_\_\_ seats Clasping and Reciprocation areas \_\_\_\_ Planes Soft Tissue areas/extensions Not \_\_\_\_ in any area Dense & bubble free casts
rest
guiding
distorted
Design Transfer Procedure
1. Determine that the ____ master casts are acceptable.
a. The cast is free from ____, voids and large nodules
b. All areas within the design of the diagnostic cast are clearly encompassed within the final ____.
c. All small nodules that do not interfere with the framework fit are carefully ____. If large nodules are present within critical areas such as the rest seat preparations, then a new ____ is indicated.
final bubbles master cast removed master cast
Design Transfer Procedure
2. Remount the diagnostic casts on the ____ table using the tripoding marks.
3. Choose 3 new ____ marks that are touched by the stylus (locked in position). These should be ones that would be easily located on both of the casts.
surveying
tripod
Design Transfer Procedure
4. After placing the 3 new widely separated marks on the diagnostic cast transfer these 3 marks in exactly the same place on the ____ (this is done off the surveyor).
5.Remove the diagnostic cast and accurately tripod the ____ cast on the surveyor using these 3 new marks.
master cast
master
Design Transfer Procedure
6. On the master cast, using the carbon ____ all survey lines on the teeth and all soft tissue undercuts.
7. Carefully, without abrading, mark in blue all retentive ____ and in red outline all ____.
marker mark
undercuts
occlusal or incisal rests
Design Transfer Procedure
8. Using the diagnostic cast as a guide, outline the metallic framework and the resin finish lines in ____.
* This design on the master cast must be the same as the one on the ____ cast (but can and should be more clean and neat!)
**The cast is now ready for ____ & duplication.
red
diagnostic
blockout
Blockout of the Master Cast
All portions of the finished metal framework are rigid and nonflexible, except the retentive ____. Rigid metal will not “spring” into an undercut!! Therefore, to allow passive yet precise fit all areas that would interfere with this placement must be ____ out.
clasp tips
blocked
• we have a design, we’re picking a common path of draw, here we have teeth that are tipped
• one design is to make the common path of draw come off the molar so the patient would seat the prosthesis on
that ____
• another possibility would be to have it guide off the premolar, but if we’re guiding off premolar then we have this large ____ that framework can’t go into or else it will lock into the patient’s mouth
• we split the difference and cut some guide planes but there’s still gonna be undercut that needs to be blocked
out
molar
undercut
Blockout of the Master Cast
Purpose:
Casts are blocked out to eliminate ____ areas on the master cast that would be crossed by ____ parts of the partial denture framework.
undercut
rigid
Blockout of the Master Cast
Additional areas to be blocked out, waxed or relieved are:
1. Beneath ____ to avoid soft tissue impingement.
2. Areas to provide for the future addition of acrylic ____ material.
3. Placement of ____ on which clasp arms are to be placed.
connectors
resin denture
ledges
• if we look at this schematic, we have a lot differences between our maxillary and our mandibular
• in the ____ we want to use the support of the palate and we want to prostheses to touch the tissue
◦ we are beading, so we have more intimate contact with our major connector in the maxillary
• but when we get to the ridge, unless we’re doing a metal base, we need to create a space
• the dark pink is acrylic
• we are using the gray block out wax to allow the space to be created
• this is a tissue stop
◦ this is always placed so that when the prostheses goes in, even in the saddle area, there is a positive place for the prostheses
◦ otherwise, if you’re thinking about fitting the framework, it would move a little bit ◦ when you’re fitting it, there is one spot where it touches and that’s the tissue stop
in the ____ it’s different
we’re using an acrylic base, then we want block out except for where the tissue stop is
maxillary
mandible
Blockout of the Master Cast Areas to be blocked out, waxed or relieved may be defined as : 1. \_\_\_\_ 2. \_\_\_\_ building 3. \_\_\_\_ 4. \_\_\_\_
parallel
ledge
relief
arbitrary
Blockout of the Master Cast
1. Parallel wax blockout – used for:
a. Proximal surfaces that are used as ____.
b. Beneath ____ connectors
c. In soft tissue undercuts that are to be crossed by ____
d. In deep ____ spaces that are to be covered.
e. In undercut areas on teeth that are to be crossed by the approach arms of ____ clasps.
guide plates minor rigid connectors interproximal bar
Blockout of the Master Cast
2.
Shaped (ledging) - used on the ____ and/or ____ surfaces of teeth to facilitate accurate placement of plastic or wax patterns for clasp arms.
This should only be done in the area of the ____ of the clasp, however, some technicians prefer to build-up the entire length of the clasp on the tooth (this must be done very carefully, as this cannot be altered on the refractory cast).
buccal
lingual
tip
Blockout of the Master Cast
3. Relief wax blockout – used for creating space between the ____ and the ____ or soft tissue.
a. Due to undesirable tissue contact.
• Examples: This is in areas where the major connector will contact thin soft tissue, such usually beneath ____ bars, or maxillary and/or mandibular tori.
*The dentist should specify whether or not ____ is needed.
framework
cast
lingual
relief
Blockout of the Master Cast
3. Relief wax blockout – used for creating space between the ____ and the cast or soft tissue.
b. To create space for ____ denture base material.
• Examples: Beneath framework extensions in ____ areas, beneath an area that is not well healed, and forming internal finish lines.
framework
acrylic
edentulous
Tissue stops
- incorporated into the ____
framework
Blockout of the Master Cast
4. Arbitrary – used in less critical areas to prevent the encroachment of ____ on the soft tissue and to facilitate ____ of the blocked out cast from the duplicating material.
•
Examples: All gingival ____, spaces between teeth that are not in the design, gross tissue undercuts below areas involved in the design of the framework, and in tooth or tissue ____ not involved in the design but would complicate the duplication process, such as the buccal vestibule in the maxilla.
metal
withdrawal
crevices
undercuts
Beading of the Master Cast
Beading
This is not a blockout but rather a ____ of additional space for metal to contact the tissue.
creation
Beading of the Master Cast
Beading
Purpose:
To create additional metal material to contact the ____ around the ____ connector to provide a snug fit, which helps prevent ____ particles from collecting beneath the framework.
palate
major
food
Beading of the Master Cast
Beading
This is also used to determine if the PRDP has a good ____ to the underlying tissue it contacts.
fit
Beading Procedure
Beading
Use a small spoon excavator to scrape the cast along the anterior and posterior borders of the major connector, where indicated.
1. Should not exceed ____ mm in depth!
2. Should be incorporated in ____ tissue or minor glandular tissue, and it should fade out as it approaches the ____ tissue (____ mm from the free gingival margin tooth border) or as a prominent area in the ____ is approached.
1 keratinized unkeratinized 2-3 midline
Blockout Procedure
Problems Usually associated with failure to \_\_\_\_ and obturate undesirable undercuts, inaccurate placement of blockout wax, over relieving, under relieving, and beading that is either too shallow or too deep. This results in frameworks which: Cannot be \_\_\_\_ \_\_\_\_ into place Have no \_\_\_\_ \_\_\_\_ on soft tissues
identify seated snap retention impinge
Duplication of the Master Cast
The surveyed and prepared have been blocked out and ____ as indicated.
The cast is then duplicated to produce an exact copy of the master cast in investment material. This is called a ____ cast because it contains ceramic material that permits ____ of the waxed-up framework and casting of metal.
beaded
refractory
burnout
Duplication of the Master Cast
____ hydrocolloid is used to make the mold for duplication. Alginate irreversible hydrocolloid may also be used if you increase the water volume to ____x the volume used for a regular impression. This thin mixture can be poured into the duplicating flask (which hold the mold).
reversible
3
Preparation for Waxing of the PRDP Framework
1. Soak the prepared cast in heated ____.
2. Remove the cast and let it ____ and harden.
The cast is now ready for framework waxing.
beeswax
drain
