Altered cast tech

1. Fabricating Removable Partial
Denture Bases

2. (1) Factors Affecting Selection of Artificial Teeth
(2) Altered Cast Technique
(3) Procedures for Articulating and Restoring
VDO
(4) Procedures for Arranging Artificial Teeth and
Waxing Up Denture Bases

3. (1) Factors Affecting Selection of
Artificial Teeth
(a) Criteria for common denture base and
artificial tooth combinations
1 Maxillomandibular space
2 Esthetic values
3 Absence of soft tissue undercuts
4 Length of edentulous space
5 Health of soft tissue and anticipated rate of
bone resorption

4. (1) Factors Affecting Selection of
Artificial Teeth
The choice of selecting acrylic or porcelain
teeth are determined by the dentist

5. (b) Types of anterior tooth and
tissue replacement
(Primary factor is esthetic acceptability)
1 Commercial facings
a Prefabricated facings retained on a metal backing with a
cementing medium
b Identical replacement possible
c May be used when undesirable soft tissue undercuts are
present
d No reline potential

6. (b) Types of anterior tooth and
tissue replacement
2 Reinforced Acrylic Pontics
a Denture teeth ground to fit an edentulous space and
retained on a metal base
b Variety of shades and molds
c An advantage over commercial facings are the improved
three dimensional effects, such as overlapping teeth
d May be used when undesirable soft tissue undercuts are
present

9. Braided Post
Used with stock denture teeth similar to RAP.
Denture teeth not needed for wax-up

10. (b) Types of anterior tooth and
tissue replacement
3 Processed tooth-colored resin
a Waxed to metal framework and processed with tooth-
colored resin
b May be used when undesirable soft tissue undercuts are
present
c Requires stable ridge

11. (b) Types of anterior tooth and
tissue replacement
4 Acrylic denture teeth with resin base
a Attached to metal retention grid or mesh
b Compensates for gross ridge resorption
c Resin base provides support and bracing
d Resin can be relined
e Requires significant vertical space
f Not recommended when deep labial soft tissue undercuts
are present

12. (c) Types of posterior tooth and
tissue replacement
1 Acrylic denture teeth with denture resin
a Attached to metal retention grid or mesh
b Denture base can be relined
c Easy to modify
d Moderately esthetic

13. (c) Types of posterior tooth and
tissue replacement
2 Metal teeth integrated into framework
a Better tissue adaptation than processed acrylic
b Requires least amount of space
c Least esthetic
3 Tube tooth attached to metal denture base
a Limited to short span, well healed areas
b Requires 4 mm posts for adequate retention

15. (c) Types of posterior tooth and
tissue replacement
4 Processed tooth-colored resins with spiral post
retention
a Short span application
b Substitute for tube teeth
c Requires slightly less interarch space than a tube tooth

17. (2) Altered Cast Technique
(a) Definition - A corrected impression of the
distal extension area(s) of the patient’s mouth,
made after the fit of the framework is
confirmed in the mouth and before artificial
teeth are arranged
(b)Purpose - This procedure is designed to ensure
the best possible soft tissue support for a distal
extension denture base

18. (c) Procedures for the Altered
Cast Technique
1 Dentist adjusts and fits the framework in the
patient’s mouth
2 Dentist designs outline of proposed impression tray
3 Plastic tray will be constructed over the
framework’s distal denture base retention
4 Adapt a 26 gauge sheet wax spacer to the edentulous
area, then adapt a second layer of 26 gauge sheet
wax to the retromolar pad and blend it with the first
sheet wax layer, trim wax to design line

20. (c) Procedures for the Altered
Cast Technique
5 Warm the distal extension grid of the framework
over a flame and place the framework on the master
cast
a Be sure the rests are fully seated
b Remove any wax that flowed over the metal
c apply separator to cast
6 Mix self curing resin to a dough-like consistency
7 Adapt resin over the edentulous area to form a tray
that is firmly attached to the retention grid

22. (c) Procedures for the Altered
Cast Technique
8 After resin is cured, lift the framework with attached
tray from the cast
9 Trim the tray to the outline the spacer forms
10 Remove wax spacer
11 Disinfect IAW manufacturer’s directions
12 Return framework to the dentist

23. (c) Procedures for the Altered
Cast Technique
13 Making the corrected impression
a The dentist makes the corrected impression
b Impression material is placed in the tray(s), then the entire
framework is seated in the patient’s mouth
c Disinfect the completed impression

24. (c) Procedures for the Altered
Cast Technique
14 Altering the Master Cast
a Draw design for saw cuts across the distal extension, from
buccal to lingual, on a line that passes 1 mm behind the
distal abutment
b Draw another saw cut line that is parallel and lingual to
the lingual sulcus to join with the first cut
c Cut along design lines
d Using a fissure bur or a saw, place multiple dovetail cuts
in the cut surface of the cast to create mechanical retention
for the corrected addition

26. (c) Procedures for the Altered
Cast Technique
e Place the framework with corrected impression on the
prepared master cast
1 Be certain all rests are in complete contact with their
respective seats
2 Secure the framework in place with sticky wax

27. (c) Procedures for the Altered
Cast Technique
f Bead and box around the borders of the impression
1 Place utility wax around the outer border of the
impression 3 mm below the peripheral roll and seal it
to both the impression and the base of the cast at the
ends of the wax
2 Seal boxing wax in place even with the height of the
base of the cast and along the outer border of the
utility wax
g Soak the base of the cast for about 5 minutes

29. (c) Procedures for the Altered
Cast Technique
h Vacuum mix stone and pour impression
1 Use manufacturer’s directions for water/powder ratio
2 Remove wax after stone sets
i Separate Cast
1 Remove framework and tray from the cast
2 Completely clean debris from the cast
3 Check the cast for voids
4 Trim cast, preserving the land area

31. (c) Procedures for the Altered
Cast Technique
j Remove acrylic resin tray
1 Flame tray until it softens
2 Peel tray from the framework
3 Clean framework thoroughly
k Seat the framework back on the cast with all rests seated

32. 1. Procedures for Arranging Artificial
Teeth and Waxing Up Denture Bases
a. Tooth arrangement
1. If try-in is going to be accomplished, tinfoil is
applied to cast over edentulous area as separator
2. Set the maxillary posterior teeth
a. Flow wax around denture base retention to seal frame to
cast
b. Lower incisal guide pin 0.5 mm
c. Set posterior teeth in maximum intercuspation
1. Marginal ridges set at same height
2. Maintain buccal alignment with adjacent teeth
3. Eccentric contacts must be avoided

33. 1. Procedures for Arranging Artificial
Teeth and Waxing Up Denture Bases
a. Tooth arrangement
1. If try-in is going to be accomplished, tinfoil is
applied to cast over edentulous area as separator
2. Set the maxillary posterior teeth
a. Flow wax around denture base retention to seal frame to
cast
b. Lower incisal guide pin 0.5 mm
c. Set posterior teeth in maximum intercuspation
1. Marginal ridges set at same height
2. Maintain buccal alignment with adjacent teeth
3. Eccentric contacts must be avoided

36. 1. Procedures for Arranging Artificial
Teeth and Waxing Up Denture Bases
a. Tooth arrangement
d. Return incisal guide pin flush with upper member
e. Grind occlusal surfaces until pin touches the table to
develop tight maximum intercuspation

37. 1. Procedures for Arranging Artificial
Teeth and Waxing Up Denture Bases
b. Wax-up
1. Snowshoe principle
a. Establish full coverage; cover ridge, mucco-buccal and
lingual folds entirely
b. Pressure is distributed over a broad surface area rather
than concentrated on a point
2. Bulk wax - from finish lines to 1 mm past blue
design line
a. Overwax 2 mm onto the external finish line; allows
finishing with no step between metal and acrylic
b. Fill peripheral roll

38. b. Wax-up
3. Gingival trim - duplicate natural tissue
a. 45 angle on the buccal side
b. 90 angle on the lingual side
4. Festooning - eminences, when contoured should
appear natural
5. Check occlusion to ensure no tooth movement has
occurred during waxing

40. (3) Finishing RPD Bases
(b)Remount the casts on
the articulator
(c) Selective Grind
Artificial teeth

41. (3) Finishing RPD Bases
(c) Restore vertical dimension
of occlusion
1 Ensure incisal pin contacts the
incisal guide table
2 Be sure to maintain contacts
in tight centric occlusion
3 Adjust Excentric excursions,
Protrusive and lateral

42. (3) Finishing RPD Bases
(d)Carefully remove RPDs from casts (don’t
break acrylic or bend out clasps)
(e) Finish
1 Trim flash using arbor bands or acrylic trimming
stone
2 Free acrylic from clasp using sandpaper discs
3 Smooth transition between acrylic and external
finish lines using rubber points and wheels
4 Borders should be round with no sharp edges

43. (3) Finishing RPD Bases
5 Use a fissure bur to grind bubbles from gingival trim
(f) Polish
1 Do not pumice festooning away - go back to
finishing for hard to get areas
2 Close attention should be given around clasps
3 Repolish metal areas as necessary
(g)Disinfect RPDs IAW manufacturer's
directions

44. Denture Base Repairs
Denture Tooth
Repair
– Box Preparation
– Matrix to position
tooth

45. Denture Base Repairs
Denture Base
Fracture
– Rabbet Preparation
– Position on cast

46. Denture Base Repairs
Denture Base
Reline
– Reline Jig