A novel digital altered cast impression technique for fabricating a removable partial denture with a distal extension

1. Journal Club Presentation
Neeraja M Menon
2nd MDS

2. A novel digital altered cast impression
technique for fabricating a removable partial
denture with a distal extension.
Wu J, Cheng Y, Gao B, Yu H. The Journal of the American Dental
Association. 2020 Feb 17.

3. CONTENTS
✔ Aim
✔ Introduction
✔ Materials and method
✔ Result
✔ Discussion
✔ Conclusion
✔ Related articles

4. .
AIM
✔ The objective of the study is to determine an
alternative technique for constructing the altered
impression and cast via digital methods

5. INTRODUCTION
✔ The altered (corrected) cast impression technique
is commonly used in the distal extension of partial
removable dental.

9. ✔ It is a labor-intensive and time-consuming clinical
procedure.
✔ Significant errors occur if the framework does not fit
or is not fully seated during the impression or
laboratory phase of fabricating the altered cast.
✔ This novel digital altered cast impression technique
may eliminate interoperator variability and increase
precision compared with the traditional technique.

10. CASE REPORT

11. Conventional
impression was made
Cast poured with type
IV dental stone
Jaw relation recored
and bite registered
Mounted on an
articulator
The casts and the
relation was scanned
and data imported to
software.
Electronic surveying
was performed.
A novel custom tray
with record rims and
window was
designed.
.
The altered cast
impression was made
with soft polyether
impression material.
At the same time, jaw
relation record were
obtained using PVS
registration paste
Border moulding
was done using
Modeling plastic
impression
compound
The border and
tissue surfaces
of the bases
were adjusted
in the mouth

13. The altered cast was
poured with type IV
dental stone and the cast
was digitally scanned
The primary and altered
cast images were
precisely matched with
Geomagic Studio
software
The data for the distal
extension on the primary
cast were removed and
replaced with the data
images of the altered
cast
The data were
reconstructed into a
digitized mandibular
altered cast
The digital RPD
framework was designed
on the digital altered cast
Using the scan data and
design, the polymerized
cast was fabricated with
methacrylate using digital
light procession
The titanium alloy RPD
framework was
manufactured using a
selective laser melting
machine
The framework was
polished and the RPD
framework was fitted and
adjusted on the cast and
then placed in the
patient’s mouth.
The denture bases were
processed with a lost-
wax casting injection-
molding process.

15. ✔ The quality of the fit of the final prosthesis was evaluated as
good with fit checker material (Fit Checker II, GC).
✔ At the 6-month follow-up examination, the RPD fit well and was
tolerated without discomfort to the patient.

16. DISCUSSION
✔ Results of several studies have shown the
advantages of altered cast technique include
increased support for the base and decreased
forces on the abutment teeth and the RPD
fabricated using an altered cast impression is
believed to improve patient comfort and preserve
oral health.

17. ✔ With the development of CAD-CAM RP methods, it has been
suggested that altered cast procedures can be performed in
a more cost-effective and efficient manner.
✔ The novel impression method, these labor-intensive steps
can be digitally combined, and the clinical time for dentists
and 5 or 6 appointments needed for the traditional RPD
treatment can be reduced to 3 visits. The RPD fabricated by
CAD-CAM SLM can be delivered to the patient within 3
through 5 days.

18. ✔ Conversely, intraoral scanning still lacks accuracy and
there are difficulties in capturing soft tissues. Therefore,
the development of novel intraoral scanning is expected
to improve the reliability and accuracy of a fully digital
approach in the future without a physical cast.

19. CONCLUSION
✔ Based on the article, it can be concluded that digital
and 3D printing technologies show the potential of
obtaining a digital altered cast impression of RPD with
distal extension.
✔ Furthermore, with improvements in the software, the
number of clinical appointments, chair time, and
laboratory procedures can be reduced.

21. A stereolithographic resin pattern for evaluating
the framework, altered cast partial removable
dental prosthesis impression, and
maxillomandibular relationship record in a single
appointment.
Lee, J.H. and Lee, C.H., The Journal of prosthetic dentistry, 114(5), pp.625-626.

22. AIM
✔ To introduces an alternative technique for the
evaluation of the framework, altered cast partial
removable dental prosthesis impression, and
maxillomandibular relationship record procedures
at the same appointment with computer-aided
design/computer-aided manufacturing
(CAD/CAM) and rapid prototyping (RP)
technologies.

23. TECHNIQUE
✔ After scanning the cast, design the framework
according to removable prosthodontic principles
with CAD software.

24. ✔ Make the altered cast partial dental prosthesis
impression trays that are based on the original
framework design.

25. ✔ Transfer the finished design information of
the framework to a rapid prototyping
machine (ProJet DP 3000; 3D Systems).
✔ Make a stereolithographic resin pattern of
the framework and cast it.
✔ Print the other 1-piece stereolithographic
resin structure of the altered cast
impression trays and the record rims.

26. ✔ Evaluate the cast framework and adjust it to fit in the
mouth.
✔ Make the altered cast impression with a modeling
plastic impression compound (Peri Compound; GC
Corp) for border molding and a polyvinyl siloxane
material (Examixfine Injection Type; GC Corp).
✔ Obtain the maxillomandibular relationship record with
a polyvinyl siloxane occlusal registration material

27. ✔ After making the altered cast, mount the casts in an
articulator with the maxillomandibular relationship
record. Remove the 1-piece sterolithographic resin
structure from the altered cast and place the cast
framework. Arrange the artificial teeth for trial placement.

28. DISCUSSION
✔ With CAD/CAM/RP technologies, the 1-piece
stereolithographic resin structure is used for making
the framework evaluation, altered cast impression,
and maxillomandibular relationship record in a single
appointment.
✔ The number of patient visits, chair time, and
laboratory procedures are reduced with this
technique.

29. An In Vitro Investigation of Accuracy and Fit
of Conventional and CAD/CAM Removable
Partial Denture Frameworks
Soltanzadeh P, Suprono MS, Kattadiyil MT, Goodacre C, Gregorius
WJournal of Prosthodontics. 2019 Jun;28(5):547-55.

30. AIM
To evaluate the overall accuracy and fit of
conventional versus CAD/CAM removable partial
denture frameworks based on standard tessellation
language (STL) data analysis, and to evaluate the
accuracy and fit of each component of the RPD
framework.

31. MATERIALS AND METHOD
✔ A 3D printed model of a maxillary arch with a
Kennedy class III modification I situation was
fabricated.

32. ✔ Forty impressions (conventional and digital) of the master cast
were made and divided into 4 groups based on fabrication
method.
.

33. ✔ RPD frameworks were fabricated in cobalt-chromium
alloy.
✔ All frameworks were scanned, and the gap distance
between the framework and scanned master model was
measured at 8 locations
✔ Data were statistically analyzed using the Kruskall-Wallis
test, followed by the Bonferroni method for pairwise
comparisons.

34. RESULT
✔ A gap from 0 to 50 μm was considered close
contact (no gap), and a gap from 50 to 311 μm
was defined as clinically acceptable fit.
✔ The lowest value (best fit) for overall framework
adaptation was obtained from the conventional
group, and the highest value (worst fit) was
found with the CAD-printing group.

35. ✔ There was no significant difference between the
conventionally cast frameworks (group II and group IV),
or between the 3D-printed frameworks (group II and
group III).
✔ The biggest gap (0.33 mm ± 0.20 mm) was observed
with the anterior strap of the major connector with the
printed frameworks (groups II and III).

36. ✔ The mean values measured for rests, posterior
straps of major connectors, and reciprocal plates
from all groups were less than 50 μm, and were
considered as close contacts.
✔ For the major connectors, the lowest values obtained
were from conventionally cast frameworks (0.04
mm), and were significantly different when compared
to the printed frameworks (0.2 mm)

37. Conclusion
✔ Although both conventional and 3D-printing
methods of framework fabrication revealed
clinically acceptable adaptation, the
conventional cast RPD groups revealed better
overall fit and accuracy.

38. Use of intraoral scanning and
3-dimensional printing in the
fabrication of a removable partial
denture for a patient with limited
mouth opening
Wu J, Li Y, Zhang Y. The Journal of the American Dental
Association. 2017 May 1;148(5):338-41.

39. AIM
To improve the efficiency and quality of fabricating an
RPD framework by integrating the technologies of
intraoral scanning, computer-aided design, and 3D
printing.

40. CASE REPORT

41. ✔ The mesial occlusal rests on teeth nos. 16 and 25 were
prepared, and the vertical distance was recorded.
✔ An intraoral video scanning system (CEREC Omnicam,
Dentsply Sirona) was used to perform intraoral scanning.
✔ Multiple overlapping scans were made to collect enough
data.
✔ Then the data was united by using software (Mimics
17.0, Materialise) and reconstructed the digitized
maxillary dentition defect cast in the standard
triangulation language file format.

43. ✔ By means of 3D printing, the polymerized cast was
made and the RPD was virtually designed and with
3D printing technology, then the titanium alloy RPD
framework was fabricated with adequate supports by
using an SLM machine

44. ✔ The RPD framework fit the 3D printing polymer cast
well. Then the 3D printing framework was polished
and made the RPD by means of the injection
molding process.

45. DISCUSSION
✔ During impression procedures, a wide mouth
opening is required for proper tray insertion and
alignment.
✔ Baker and colleagues, outlined and illustrated a
method of using sectional, locking custom
impression trays for such patients.

46. ✔ Although it can simplify the manipulation and
decrease the patient’s trauma, the additional time,
materials, and labor made this method more
complicated.

47. ✔ With the development of the intraoral scanning
system, clinicians can reconstruct highly accurate 3D
surfaces of teeth or mucosa and record them in a
short time, which allows them to make accurate
impressions for patients with limited mouth openings.

48. CONCLUSION
✔ Unlike the traditional method, this integrated system
has the potential to design a custom-made dental
prosthesis and directly make an RPD framework with
complicated patterns.

49. Comparison
Between Altered Cast Impression and
Conventional Single-
Impression Techniques for Distal
Extension Removable Dental
Prostheses: A Systematic Review
Sayed M, Jain S The International journal of prosthodontics.
2019;32(3):265-71.

50. AIM
✔ To systematically review the available literature and
determine the potential benefits of altered cast
impression technique over conventional single-
impression techniques for the fabrication of distal
extension removable dental prostheses.

51. MATERIALS AND METHODS
✔ The indexed English literature published up to April
30, 2018, was systematically searched for studies
comparing altered cast impression technique to
conventional single-impression techniques for the
fabrication of distal extension removable dental
prostheses using guidelines recommended by
Preferred Reporting Items for Systematic Reviews
and Meta Analyses (PRISMA).

52. ✔ The databases searched were PubMed, the
Cochrane Library, and MEDLINE (OVID).
✔ Two reviewers independently screened and
shortlisted the relevant studies based on predefined
inclusion and exclusion criteria

53. RESULT
✔ Seven studies were included in this review; all were
in vivo studies.
✔ All seven studies reported that cast removable
partial dentures fabricated with altered cast
impression technique displayed less vertical
movement of denture bases compared to those
fabricated using conventional impression techniques.

54. ✔ Two of these studies reported that this difference in
vertical movement was clinically insignificant, while
the other five studies reported a statistically
significant difference in vertical movement but were
uncertain regarding clinical significance.

55. CONCLUSION
✔ The results of this literature review indicate that the
altered cast impression technique did not offer
significant advantages over conventional single-
impression techniques.

56. ✔ The lack of convincing data to predict superiority of
the altered cast impression technique for distal
extension removable dental prosthesis impressions
emphasizes the need for more scientific research
with larger sample sizes and longer performance
reviews of removable dental prostheses.

57. Thank you..
..And stay sa