altered cast

1. Altered-cast technique:
Overview around research and articles
Supervision : Dr. Runak
Prepared: Ammar G. Salem

2. introduction
 It was originally described more than 80 years ago.
 It was developed to improve the residual ridge to dentition relationship of
the prosthesis.
 This technique has the potential benefits of reducing the number of
postoperative visits, preserving the residual ridges, improving stress
distribution, decreasing food impaction and decreasing the torqueing of
abutment teeth.

3. What is successful RPD (Steffel)
 Cross-stability of the framework.
 Maximal coverage of the edentulous residual ridge.
 Stress control.

4. According to Becker and Kaiser
 Rigid major connector.
 Multiple positive rest seats.
 Mesial rests.
 Parallel guide planes.
 I-bar clasp design.
 Altered-cast technique
 The single most important factor in minimizing abutment tooth movement is the
fit of the base. (Tylor and colleagues, Tebrock and colleagues)
 The tissue surface of the distal extension RPD should cover the residual ridges at
the most relaxed state when not in function.

5. Importance of altered-cast technique
 Holmes and Leupold showed that the altered cast impression technique
demonstrated the least amount of movement of the base at the time of
placement and the most favorable ridge-to-denture-base relationship.

6. Basic technique
 The custom resin tray covers the occlusal surfaces of teeth with a minimum of
three definitive stops to ensure repeatable placement in the mouth each
time.
 The edentulous ridge was covered with single sheet of wax.
 Using fluid wax korecta Wax I-IV applied to tissue surface of the tray, it was
applied incrementally to achieve the final impression.

7. What were the objectives of Applegate
 The area covered should be maximized to minimize the work of any given
surface.
 Traumatic impact on any area must be avoided so that the workload is spread
as uniformly as possible to avoid impinging on areas with less displaceable
mucosa.
 At rest, there must not be any areas of ischemic mucosa.
 All areas under load must receive stimulation.
 Simultaneous support must be given to the base and the supporting teeth.
 Movable border structures should be extended during the making of the
impression to avoid impingement on any functional movement after
completion of the base.

8. Technique
 The impression material should be very accurate and easily manipulated to record
the remaining dentition. (in this case you can use elastomeric impression
material, or hydrocolloid in a stock metal tray.
 The residual ridge has two forms:
 Functional: when tissue is under load.
 Anatomic: when tissue at rest.
 It is desirable to record the residual ridge in its functional state, thus the material
used to register the ridge may not be suitable to record the teeth.
 For this reason the RPD framework is cast and fitted before the altered cast final
impression is made.
 This ensure that the metal framework and the base will be related in the same
relationship as that which exist between abutment tooth and the supporting
mucosa when the base has an occlusal force applied.

9. Technique (continue)
 Once the framework is fit, an acrylic resin custom tray attached to the metal
framework on the physical retainer.
 The tray then border-molded (using impression compound).
 Place some vent holes in the tray over the ridge crest and retromolar pad.
 Final impression is done with polysulfide rubber impression.
 The framework attached to a custom tray that is lined with a wash of
impression, is placed in the patient’s mouth and seated completely without
any pressure on the tray.
 The finger pressure is applied only to the parts of the framework that in
contact with teeth.
 Pressure on the tray area can cause lifting off of the framework off the teeth.

10. Improper impression can result :
 Overstimulation of the underlying bone (due to too much work and poor
stress distribution).
 Understimulation of the softer mucosa (due to too little or no work).
 Destructive leverage applied to abutment teeth.

11. Final impression

12. Laboratory procedure
 Two saw cuts are made perpendicular to each other.
 1st cut 0.5-1.0mm distal to the most distal remaining tooth and perpendicular
to the edentulous ridge.
 This cut carried from outer edge of the cast to 6.0-7.0mm medial to the
lingual vestibule.
 2nd cut made parallel and medial to the edentulous ridge, extending from the
most posterior aspect of the cast to the most medial aspect of the 1st cut.
 1st and 2nd cuts intersect, the edentulous ridge will separate from the cast.
 In case of maxillary arch, provide the internal finish line of the framework
processed against the altered cast.

13. Lab procedure (continue)
 The cut surface should have grooves to aid retention of newly poured stone.
 Completely seat the framework on the cast.
 Lute the framework to the cast via sticky wax.
 (an error at this stage will create prosthesis with faulty relationship between
the edentulous ridges and the remaining dentition).
 Bead and box, then soak in a cool water bath to saturate the base of the
remaining cast.
 Using model stone type III poured and wait to set in minimum 45 minutes.
 After the cast prepared remove the acrylic resin tray from the framework.
 The frame then fitted back to the cast.

17. Making an index tissue stops
 It is mandatory that the occlusal rests be
completely seated during both clinical
and laboratory procedures to avoid over-
or under-displacement of the soft
tissues.
 For patients with few anterior teeth
remaining, a condition result in long
distal-extension ridges in which the
rotational stability of RPD is mainly
tissue dependent.
 As can be seen tissue stops are touching
the cast on crest ridge.

18. Procedure
 For stabilizing the framework in class I
Kennedy, tissue stops are commonly used to
contact the edentulous ridges of the cast.
 A 3rd reference point (stone index) placed
under the lingual bar must be used before
altered-cast impression is made.
 Why? Because the tissue stops will be covered
by the impression material and will be useless
for re-orienting the framework to the altered-
cast.

19. Procedure
 The idea of the stone index is to aid the
occlusal rests in orientation of the
framework to the master cast.
1. Fabricate the framework for RPD and
refine its fit intraorally.
2. Place the framework on the master cast
and fill the space under the bar with
stone.
3. While the framework is on the master
cast, adapt acrylic resin over its
latticework to make a custom
impression tray.

20. Procedure
4. Make a corrected impression of the distal
extension residual ridges at the established
vertical dimension of occlusion and
horizontal jaw relationship.
5. Alter the master cast by aremoving the
residual edentulous ridgend reposition the
completed impression on the sectioned
master cast. The secure it with sticky wax
around the clasp arms.
6. Box the cast and add dental stone to the
impressions of the edentulous portions to
make the altered-cast.

21. Procedure
7. Soak the poured altered-cast in warm
slurry water to soften the impression
material, clean the cast, and reposition the
cleaned metal framework onto the lingual
index of the altered cast.

22. Making framework try-in, altered cast
impression and occlusal registration in one
appointment (Introduction)
 This method use detachable custom-made prefabricated impression trays.
 It uses this impression as a stable recording base to make the jaw relation
record .

23. Making framework try-in, altered cast
impression and occlusal registration in one
appointment (Procedure)
1. Apply the separating medium on the
master cast.
2. Place the framework on the master cast.
3. Block out all undercuts around the
retentive grid on the edentulous portion of
the framework with wax.
4. Make individual impression trays over the
distal extension bases with
autopolymerizing tray resin.

24. Making framework try-in, altered cast
impression and occlusal registration in one
appointment (Procedure)
5. Remove the tray and trim the excess resin.
6. try-in the framework and adjust it to fit.
7. Place the framework on the master cast and
attach the prefabricated trays with
autopolymerizing resin.
8. adjust the borders and tissue surface of the
bases in the mouth. Examine the thickness of the
tray to be certain that it does not interfere with
the occlusion.
9. Remove any interferences and prepare few
grooves as an index on the occlusal surface of
the tray to permit reseating the jaw registration
material.

25. Making framework try-in, altered cast
impression and occlusal registration in one
appointment (Procedure)
10. Make the altered cast impression with alginate or silicon impression material
and mold the material around the border as it sets.
11. Trim excess of impression especially in the occlusal surface of the denture
base.
12. Make the jaw relation record with accurate registration material (silicon,
polyether, or zinc oxide eugenol).
13. Remove the framework with the distal extension altered cast impression and
the jaw relation record from the patient’s mouth.
14. Box the framework and the altered cast impression with alginate and pour
the altered cast in dental stone.

26. Making framework try-in, altered cast
impression and occlusal registration in one
appointment (Procedure)

27. Making framework try-in, altered cast
impression and occlusal registration in one
appointment (Procedure)
15. mount the maxillary and
mandibular casts in articulator
with the jaw record.
16. After mounting the cast,
remove the registration material,
impression trays, and impression
material from the framework.
(using hot water or alcohol
frame to soften the material).
17. set the teeth and process,
finish and polish.

28.  The undercuts are blocked out with wax in the retentive grid areas where
impression trays will be attached.
 The surfaces need block-out beneath the retentive grid and around soldered wire
clasps.
 Separating medium is applied to the cast, framework and block-out.

29. method to register the mucosa and its
supporting form
 Functional reline; after the denture base has been processed onto the
framework, it has disadvantage of greater degree of occlusal adjustment
after the processing of acrylic resin.
 Altered-cast method; carried out before the denture bases are processed.

30. Other method to separate the edentulous
portion from the rest of the cast
 Separating the cast without use of the plaster saw.
 Advantages:
 Edentulous portion can be separated easily.
 No need to saw the cast or make dovetails for retention.
 Edentulous portion can be separated even if cast is wet.
 Disadvantage:
 The cast cannot be used with hydrocolloid impression because it require quick
pouring of the impression.
 The impression cannot be boxed because it will distort as a result of pressure.

31. Other method to separate the edentulous
portion from the rest of the cast (Procedure)
1. Make a bar with baseplate wax with shape of a 5mm equilateral triangle in
cross section. It should be made in advance to save time.
2. Cut several pieces of the wax bar 15mm long and set them aside.
3. Box the elastomeric final impression.
4. Separate the edentulous ridges distal to the last tooth in the impression by
contouring a piece of baseplate wax to fit the anatomic contour of the
impression, and seal it to the base to make three separate compartments of
the impression. If separating wax is not close enough to the distal surface of
the last tooth of the impression, the edentulous portion of the cast left distal
to the last tooth can be trimmed after the edentulous pieces of the cast are
removed.

32. Other method to separate the edentulous
portion from the rest of the cast (continue)
 5. wax the 15mm long pieces of triangular wax bars to the separating baseplate
wax. Make the apex of the triangle sealed securely to the separating baseplate
wax toward the tongue side and anterior to the edentulous ridge.
 6. fill the three compartments with dental stone above the level of separating wax
to make a master cast.
 7. after setting of stone, remove the boxing wax and impression and trim the base
of the cast until a stone base at least 3 to 5 mm thick remains below the
separating wax. (to prevent premature separation).
 8. after making framework, and fitted to the cast and patient’s mouth, place the
framework on the cast and adapt a shellac baseplate or form an acrylic resin
baseplate over the edentulous retention portion of the ridges and proceed to
make the impression. After displacement impression is made, separate the
edentulous portion of the original cast and discard it, to permit placing the
framework with the new impression on the original cast.

33. Other method to separate the edentulous
portion from the rest of the cast (continue)
 9. soak the cast in slurry water for 3-5 minutes and trim the base of the cast
up to the line to expose the separating wax.
 10. put the master cast in boiling water for 5 minutes. The clear slurry water
should be saturated with stone in order not to dissolve the cast.
 11. after melting the wax, the edentulous portions will be separated from the
rest of the cast and dovetails will appear.
 12. flush to remove all wax, seat the framework with the new impression and
pour the new portions of the cast. (if too much of the old edentulous ridge is
left, the framework with the new impression may not seat well. (use sharp
knife to trim the ridge back to the distal side of the last tooth).

34. Other method to separate the edentulous
portion from the rest of the cast

35.  In 2004, (Richard et al.) compared between altered case and one-piece cast with
regard to base support, abutment health, and patient comfort over time. He
reported that the altered cast impression procedure does not offer significant
advantages over the one-piece cast, provided the standards used in his are met,
including a completely extended impression, use of magnification to adjust and
ensure complete framework seating, and coverage of the retromolar pad and
buccal shelf by the base.
 He reported that those studies which are in favor of ACIP did not involve more
than 7 subjects and 2 studies and the evaluation of base support done in a manner
not used in clinical practice.
 It was hypothesized that there would be no difference between the ACIP and OPC
relative to these variables: border extension, frequency/amount of base
adjustment needed, base movement, base adaptation, need for reline, changes in
direct abutment mobility, gingival index, sulcus depth, quality of posterior
occlusion, health of tissues beneath the RPDs, patient satisfaction, time worn, and
soreness reported by the patient. All were accepted in the result except for border
extension and adaptation of the base to the ridge crest.
 Under extension was noted in 22% of the OPC and in none of the ACIP.
 Causing of under-extension could be: difficulty to recognize anatomical
landmarks, underextended impressions, under-waxed or over-finished bases,
aggressive base adjustment, lack of space, or patient demand.

36.  Although Maxfield et al. reported that ACIP decreases the load on the direct
abutments, it does not appear that such difference has any detrimental
effect. But the increase in inflammation around the direct retainer
underscores the importance of periodic reinforcement of oral hygiene
instructions (Bregman et al)
 To substitute ACIP, three conditions should be met; a framework that exhibit
complete seating under x2.5 magnification, the impression records all
applicable landmarks, and the base extension is neither under-extended nor
over-finished.
 Otherwise, the practitioner should either use the ACIP, a custom impression
tray, or evaluate base movement during framework evaluation with an
attached occlusion rim (if movement is noted ACIP should be performed).

37. Framework fit and altered cast impression
 Problems that may arise because the impression material being placed between
framework and mucosa, which lift away the framework from the mucosa; subsequently,
during flasking, the framework will depress again, producing inaccuracies in the
prosthesis.
 Pressing down on the framework while making the impression, may give inacceptable
results, because it is difficult to judge how much pressure to exert; in addition, the act of
pressing down may itself cause slight displacement.
 An alternative approach is to take the altered cast impression first, and then to obtain
jaw relation record in silicon; however, major two disadvantages come ahead; first, it is
difficult to ensure that the framework will remain in the correct position. Second, the
impression material used for obtaining the jaw relation record may be displaced slightly,
leading to inaccuracies in the final structure.
 Another approach is to use the framework as record base; however, this procedure is
also sometimes inaccurate.

38. Framework fit and altered cast impression
 Check the fit of framework for its passive fit and absence of occlusal interferences.
 Make a tray base by light-cured acrylic resin, modeling compound or thermoplastic
baseplate material.

39. procedure
1. Build ¼ inch diameter column of light-cured resin on the resin-retention part of the
framework in the position corresponding to the hole in the acrylic resin tray. Extend
the column up to the opposing occlusion in the correct jaw relation. This tripod of
anterior teeth and two columns distally ensures the framework seating in the same
way each time.
2. Remove the framework and seat it on the master cast and mount it on an
articulator with an opposing cast. A stone index prepared below the lingual major
connector, facilitating and improving positioning when the framework is reseated
on the altered master cast. Enlarge the holes, if necessary, in the bases so that they
fit correctly over the resin columns. Seat the bases over the framework and heat
them and adapt them to the framework, making certain that they are firmly
attached to it.

40. Procedue

41. Procedure
 3. place framework with the base in the mouth and relieve over-extensions and
pressure spots, then apply low heat softened compound to the borders and border
mold it.
 4. remove the framework-tray complex, apply impression wax into the tray, then
reinsert the whole structure and maintain it in the mouth while the wax adapts to
the edentulous ridge. Ask the patient to make molding movements.
 5. remove the edentulous ridge from the cast by two cuts, longitudinal and at right
angle to the longitudinal axis of the ridge, 1mm distal to the abutment.

42. Procedure

43. Procedure
 6. score the cut surfaces with a knife or bur to ensure good attachment of the new stone
to the old.
 7. position the framework-impression assembly on the cast, making sure the framework
seating correctly on the teeth and in the index for the bar. If there is any chance of
change in positions during the boxing procedure, wax it securely in place with sticky
wax.
 8. bead and box the cast with wax. And seal it very well.
 9. pour a mix of stone and allow it to set.
 10. remove block-out and boxing from the cast but do not separate framework-
impression assembly from the cast.
 11. mount mandibular cast in articulator after reassuring the correct position of resin
against maxillary cast.
 12. remove framework-impression assembly.

44. procedure

45. Discussion
 The index overcome the problem of too much or less pressure exerted during
impression, ensuring correct position during impression taking.
 The index act as jaw relation record.
 This photochemical index is more reliable than elastomeric material which does not
remain joined to the impression.
 A minor disadvantage, if the patient has an antagonist edentulous area. To avoid
such problem instruct the patient not to clench tightly, but simply bring the
maxillary and mandibular arches together
 Advantages; molding can be made with mouth closed, require little time, can be
performed in clinic without new jaw relation trays, obviates the stage of functional
and harmonious occlusion, and stable and rigid jaw relation index.

46. Stereolithographic resin pattern
 Using CAD/CAM/RP technologies, a one-piece stereolithographic resin structure is used
for making framework evaluation, altered-cast impression, and maxillomandibular
relationship record in a single appointment.
 Procedure:
1. Scanning the cast, then design the framework with CAD software.
2. Make altered cast impression trays based on the original framework design.
3. Transfer the finished design to rapid prototyping machine.
4. Make a stereolithographic resin pattern of the framework and cast it.
5. Print the one-piece stereolithographic resin structure of the altered cast impression trays and
record rims.
6. Make altered cast impression with compound border molding and polyvinyl siloxane material.
Obtain maxillomandibular relationship with occlusal registration material.
7. Mount the cast in the articulator, remove the 1-piece stereolithographic resin structure from
the altered cast and place the cast framework.

48. Using altered-cast technique in prosthetic rehab
of a patient after a maxillectomy
 After primary impression capturing the crowns was made with irreversible
hydrocolloid impression material. This captures all the intraoral structures of non-
resected side and part of the resection defect with sufficient extension for the
production of a cast framework for the maxillary obturator.
 Poured with dental stone, a maxillary obturator cast framework produced from Co-
Cr-Mo alloy. The cast framework was modified in such a way that retentive mesh
and dowels were added over the resection defect to ensure retention for secondary
alter cast impression material and for acrylic resin bulb of the obturator.
 An altered cast impression was made with condensation high and low viscosity
silicone materials placed on and inserted intraorally with the obturator framework
serving as the tray.

49. Procedure (continue)
 The stone cast was altered and the portion of the cast corresponding to the
resection defect was trimmed until it was possible for the obturator cast framework
to be place on it with altered cast impression, then it was poured in dental stone.
 The predicted shape of maxillary sinus was formed by using polyvinyl siloxane to
produce a concave shape of the obturator toward sinus cavity.
 The hollow bulb obturator was made by pouring autopolymerizing acrylic resin in
the newly formed resection defect on the altered cast, covering retentive elements
of the case framework.

51. References:
 Santana-penin U., Gil Lozano J. 1998, ‘an accurate method for occlusal registration and altered-cast impression for removable partial
dentures during the same visit as the framework try-in’, the journal of prosthetic dentistry, vol. 80, no. 5, pp. 615-618.
 Ansari 1994, ‘a new procedure for separating the edentulous distal extension portion from the master cast when an altered cast is
made’, the journal of prosthetic dentistry, vol. 72, no. 6, pp. 666-669.
 Daniel B. 1999, ‘the altered cast technique revisited’, JADA, Vol. 130, October, pp. 1476-1481.
 Frank Richard P., Brudvik James S., Noonan Carolyn Jean 2004, ‘clinical outcome of the altered cast impression procedure compared
with use of a one-piece cast’, the journal of prosthetic dentistry, Vol. 91, no. 5, pp. 468-476.
 Lay Lih-Shou, Lai Wing-Hong, Wu Chen-Tsye 1996, ‘making the framework try-in, altered-cast impression, and occlusal registration in
one appointment’, the journal of prosthetic dentistry, Vol. 75, no. 4, pp. 446-448.
 Lee Ju-Hyoung, Lee Cheong-Hee 2015, ‘a stereolithographic resin pattern for evaluating the framework, altered cast partial removable
dental prosthesis impression, and maxillomandibular relationship record in a single appointment’, the journal of prosthetic dentistry,
Vol. 114, no. 5, pp. 625-626.
 Lund Peter S., Aquilino Steven A. 1991, ‘prefabricated custom impression trays for the altered cast technique’, the journal of prosthetic
dentistry, Vol. 66, pp. 782-783.
 Shifman Arie 1991, ‘index to reposition the metal framework accurately on the altered cast’, the journal of prosthetic dentistry, Vol. 68,
pp. 979-981.
 Vojvodic Denis, Kranjcic Josip 2013, ‘a two-step (altered cast) impression technique in the prosthetic rehabilitation of a patient after a
maxillectomy: a clinical report’, the journal of prosthetic dentistry, Vol. 110, no. 3, pp. 228-231.

52. Thank you for attention
Created 23/11/2019