Clinical Removable Prosthodontics Forth Year

1.  Undercut gauges used to locate retentive undercuts on proposed abutments. The degree of
undercut is measured in hundredths of inch (0.010 — 0.020 — 0.030 )
 Carbon marker used to mark the greatest circumference of the teeth. Resulting lines are termed
survey lines
 Relative parallelism of proximal tooth surfaces will determine anteroposterior tilt of the cast
in relation to the vertical arm of surveyor
 All mouth preparations must be made to conform to this determined path of insertion which
is recorded by scoring base of cast or by tripoding
 Two methods are known to record the degree of the tilt ;

Tripod method : where vertical arm of surveyor is locked at a height that allows the tip of
carbon marker to contact tissue surface of cast at three widely separated points.

Scoring method :is to score two sides & dorsal aspect of the base of the cast where analyzing
rod is placed & a line is drawn on the cast parallel to the rod. So, there are three widely spaced
lines parallel to the path of insertion
 Tripoding method
 Tripoding the cast
 Scoring method
 RETENTIVE UNDERCUTS
 Retentive undercuts must be present on the abutments, both at the horizontal (zero) tilt and at
the tilt of the selected path of insertion , to counteract any dislodgment of RPD in that direction.
 INTERFERENCES
 ESTHETICS
 Sometimes tilting the cast to avoid an interference may result in putting the clasp in an
unfavorable position for esthetics (e. g, metal display ). As such, the tilt is changed to place the
clasp tip in a better position for esthetics

 Block out
* Both hard & soft tissue areas will
require block out so that the completed

2. casting will go completely to place
along the desired path of insertion.
 Preparation of Master Cast
A- Beading of maxillary major connector.
B- Block out
C- Relief
 Master Cast Preparation
A- Beading is the act of scraping the
outline of the major connector into
the master cast.
 Master Cast Preparation
* The bead line is approximately
0.5 mm & becomes less distinct as
it approaches the gingival margin.
 Master Cast Preparation
* The bead line produces a raised edge
at the border of the major connector &
ensures positive contact of the major
connector with the palatal tissues.
 Master cast preparation
* The bead line does not run all the way
to the gingival margin
but stops 3-4 mm
from it.

3.  B- Block out
* Blocking out is the act of placing wax
and other materials into undesirable
undercuts on the master cast.
 Block out
* Both hard & soft tissue areas will
require block out so that the completed
casting will go completely to place
along the desired path of insertion.
 Parallel block out
 Arbitrary Block out sites
* Gingival margins
* Spaces between teeth
* Tissue undercuts
* Gross undercuts not in the design but would
complicate the duplication procedure.
 Arbitrary Block out
* On a maxillary cast, deep palatal defects
and irregularities are filled with wax to
eliminate potentially sharp areas on the
intaglio of the major connector.
 Arbitrary Block out

4. For mandibular cast, intimate soft tissue contact is not desirable in the anterior mandibular areas
, a thin film of wax is applied to the major connector area.
 Ledges under clasp arms
* Shaped block out or ledging is used on
the buccal or lingual surfaces.
* They guide the placement of the clasp
wax pattern on the investment cast.
 C- Relief
* Any addition of wax intended to make
the framework stand away from the
master cast is termed “Relief”.
 Cast stops
* During packing & processing the acrylic
resin the probability of bending may
occur.
* To prevent bending, a small area at the
free end of the minor connector should
contact the master cast “ cast stops “
 Cast Stops
* A cast stop is created by removing a
small square of relief wax ( 2x2mm).
* This depression is incorporated into
the refractory cast.
* During the waxing process, this depression

5. is filled with wax.