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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5199_Библиотеки_им_академика_М_И_Перельмана.pdf
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Fig. 4.11 Plan drawn on the cast
Fig. 4.12 Build the virtual meshwork pattern
(g) Build tissue stops, and draw nish lines using the
curve tool which utilizes default and customized proles (Fig.4.19).
(h) Add supports and nish the design (Figs.4.20 and
4.21).
(i) Design customized articial teeth.
Set up and align articial teeth selected from the
tooth library, and adjust them if necessary, especially
when designing a one-piece removable partial denture (Figs.4.22, 4.23, and 4.24).
(j) Design digital dental base.
Adjust the shape of the customized base when
designing a digital complete denture or one-piece
removable partial denture (Fig.4.25).
4 Digitalization inRPD
Fig. 4.13 Adjust technical parameters of the meshwork
(k) Design the one-piece RPD.
Combine all components through the Boolean
operation function of the software after the completion of the framework, articial teeth, and base to
design one- piece RPD (Fig.4.26).
5. Arrangement of the RPD
Appropriate supports of adequate strength should be
added to the polishing surface of RPD (Fig.4.27), not the
tissue surface, to avoid damaging the shape and affecting
the adaptability of the framework during manual
grinding.
6. Computer-Aided Manufacturing (CAM)
(a) Obtain metal or PEEK frameworks by CNC milling
system.
(b) Obtain metal frameworks (Fig.4.28) or resin or wax
patterns by 3D printing (Fig.4.29).
7. Post-processing and Subsequent Steps
In the case of 3D printing, metal frameworks are heat-
treated following manufacturer instructions to release the
stress (Fig.4.30) and then are separated from the supporting base (Fig.4.31), nished and polished in several steps
(Fig. 4.32), delivered to the clinic after being cleaned,
disinfected, and sterilized. RPD framework is checked for
t and occlusion intraorally and adjusted as necessary;
subsequent steps including the selection and alignment of
articial teeth, nal wax-up and polymerization of the
base, nishing, and polishing are in similar manners used
for traditional RPD.However, there’s no need to be subjected to post-processing for milled metal and PEEK
frameworks.
4.3 Digital Design Principles
Fig. 4.14 Different shape and size of the meshwork
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Fig. 4.15 Build the virtual major connector
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Fig. 4.16 Draw the clasp, rest, and minor connector three-dimensionally
4 Digitalization inRPD
Fig. 4.17 Set up the retentive pin
The 3D printed wax (Fig.4.33) or resin pattern is then
cast conventionally using lost-wax technique (Fig.4.34),
and subsequent procedures are the same. It’s worth noting
that the wax or resin pattern should be invested and casted
together with the refractory model to reduce the possibility of deformation.
Compared with 3D printed and milled metal frameworks, there is a traditional workow of spruing, investing, burnout, and casting from 3D printed resin or wax
patterns to the nal metal framework, which is complex
and has many human errors decreasing the quality of
Fig. 4.18 Adjust technical parameters of the wax
frameworks. For example, errors occurring in duplicating
the cast will result in the mist of the pattern; incorrect
ratio of powder to liquid will decrease the strength of the
investment, and then it will be prone to cracks during
casting or generate the wear debris and contaminate the
alloy; the mismatch between the expansion rate of the
investment and the alloy may result in the mist of frameworks; mixture of old and new alloys results in the uncertain expansion rate; selection of the investment is
complicated; improper setting of sprues and storage pool
will result in incomplete casting.
8. CAD/CAM of the Custom Tray
Based on the digital primary model, rstly determine
the path of insertion, block out undesirable undercuts,
and lay thin layers of virtual wax on relief areas
4.3 Digital Design Principles
Fig. 4.19 Draw the outer nish line
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Fig. 4.20 Add appropriate supports to structures
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4 Digitalization inRPD
Fig. 4.21 Finish the design
Fig. 4.22 Select and align the articial teeth from tooth library
4.3 Digital Design Principles
63
Fig. 4.23 Adjust the shape of the articial teeth as needed
Fig. 4.24 Occlusal adjustment
64
4 Digitalization inRPD
Fig. 4.25 Design the base of RPD
Fig. 4.26 One-piece RPD
4.3 Digital Design Principles
65
Fig. 4.27 Add supports to structures
Fig. 4.28 3D printed Co-Cr framework
Fig. 4.29 3D printed wax pattern
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Fig. 4.30 Post-processing for
stress release
4 Digitalization inRPD
Fig. 4.31 Manual removal of supports added to 3D printed wax
patterns
Fig. 4.33 3D printed wax pattern of the framework
Fig. 4.32 Polish the 3D printed framework
4.3 Digital Design Principles
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(Fig.4.35); then determine the extension range (Fig.4.36)
and the thickness to generate a tray with preliminary
shape; nally design the handle (Fig.4.37), and perforate
the tray virtually according to the actual needs. Export the
data after completion (Fig.4.38), and print the tray using
the resin printer.
Fig. 4.34 Cast metal framework by lost-wax technique
4.3.2 Comparison ofDigital andTraditional
Frameworks
The conventional workow, including making primary and
nal impression, making and trimming primary and nal
casts, waxing, investing, casting, nishing, and polishing of
Fig. 4.35 Primary model with relief and blockout of undercuts