Dental Sales Flyer - June 2021 - 61

Digitizing Removable Prosthetics: Case Example
The case presented for this article will identify the workflow and the
combined intraoral scanning, 3D printing, and software that allow for
designing and processing an immediate removal prosthesis following
extractions of the mandibular central and lateral incisors.
Figure 1 shows the patient at presentation, with significant periodontal
disease evident at the mandibular incisors. The patient was given the
treatment options of dental implants with cemented/bonded long-term
restorations, fixed crown-and-bridge to replace the mandibular incisors,
and extraction of the mandibular incisors preparatory to a removable
partial denture (RPD). The patient chose to extract the incisors and
accept the mandibular RPD treatment plan.
To move forward with the workflow, prior to extraction and seating of
the final RPD, rest seat preparations were completed (Figure 2). CEREC
intraoral scanning of the final rest seat preparations were acquired
and printed working models were fabricated (Figure 3). The diagnostic
images were uploaded and delivered to the laboratory.
Once the scan and files were evaluated for accuracy, the process of
designing a removeable partial framework was proposed following
an identified path of insertion (Figure 4). The steps to create the final
prosthesis included virtually blocking out undercuts, determining
clasping tip locations, establishing the finish lines of the framework,
applying tissue stops, designing the mesh, and designing major
and minor connectors (Figures 5 and 6). The laboratory prescription
identified the mandibular lateral and central incisors to be extracted at
the seating appointment for the mandibular RPD.

Figure Captions
Fig 1. Preoperative periapical radiograph.
Fig 2. Preoperative rest seat preparations.
Fig 3. 3D printed working model.
Fig 4. Design software is used to determine the path of insertion.

References
1. Progress in digital dentistry: The practical use of intraoral scanners.
Suese K. Dent Mater J. 2020 Jan 31;39(1):52-56.
2. Clinicians reaping benefits of new concepts in impressioning.
Lawson NC, Burgess JO. Compend Contin Educ Dent. 2015 Feb;36(2):152-3.
3. Accuracy and practicality of intraoral scanner in dentistry: A literature review.
Kihara H, Hatakeyama W, Komine F, Takafuji K, Takahashi T, Yokota J, Oriso K, Kondo H. J Prosthodont
Res. 2020 Apr;64(2):109-113.
4. Accuracy of digital models generated by conventional impression/plaster-model methods and
intraoral scanning.
Tomita Y, Uechi J, Konno M, Sasamoto S, Iijima M, Mizoguchi I. Dent Mater J.
2018 Jul 29;37(4):628-633.
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Zimmermann M, Ender A, Mehl A. J Am Dent Assoc. 2020 Feb;151(2):127-135.
6. Accuracy, reliability, and efficiency of intraoral scanners for full-arch impressions: a systematic
review of the clinical evidence.
Goracci C, Franchi L, Vichi A, Ferrari M. Eur J Orthod. 2016 Aug;38(4):422-8.

Figure 7 shows the final RPD delivered to the practice on a printed
model. This final removable restoration was digitally designed and
fabricated in the laboratory based on a single diagnostic imaging
appointment at the clinician's office using CEREC intraoral scanning.
The final seating appointment required local anesthetic and extraction
of teeth Nos. 23 through 26 (Figure 8). After insertion, the RPD was
adjusted only on the distal denture flange due to tight fit against
the right mandibular canine. The midline was spot on, occlusion was
verified, and minimal additional adjustment was needed (Figure 9).
The clasps and rest seats were in intimate contact with the teeth
and the overall comfort to the patient was acceptable. Due to the
hygienic design of the RPD, a 7-day follow up revealed that the RPD
did not infringe upon soft tissue resulting in a clean, pain-free oral
environment at the surgical site (Figure 10).

Conclusion
Dental practices and patients both benefit from advancements in
digital technologies. Intraoral scanning for crown and bridge, clear
aligner orthodontics, whitening trays, all-on-X implant restorations,
and removable prosthetics are available and readily integrable. Digital
workflows can be clinically and financially rewarding for both practices
and patients, and expectations for better innovations, increased
processing speeds, and ergonomic improvements to these technologies
make for an even more promising future. It may be time to drop
the spatula and mixing bowls for time-saving and accurate digital
processes that will help us serve our communities with confidence
and predictability.

Fig 5. Tissue stops are applied virtually, indicated by blue dots in the molar region.
Fig 6. Major and minor connectors are also designed using this software.
Fig 7. Final mandibular removable partial denture as shown on printed model.
Fig 8. Day of surgery, immediately following extractions.
Fig 9. The removable partial denture is seated immediately following extractions.
Fig 10. Follow-up visit 7 days following seating.
7. Impact of different scanning strategies on the accuracy of two current intraoral scanning systems
in complete-arch impressions: an in vitro study.
Passos L, Meiga S, Brigagão V, Street A. Int J Comput Dent. 2019;22(4):307-319.
8. Validity and reliability of intraoral scanners compared to conventional gypsum models
measurements: a systematic review.
Aragón ML, Pontes LF, Bichara LM, Flores-Mir C, Normando D. Eur J Orthod. 2016 Aug;38(4):429-34.
9. Using Intraoral Scanning to Fabricate Complete Dentures: First Experiences.
Goodacre BJ, Goodacre CJ. Int J Prosthodont. 2018 Mar/Apr;31(2):166-170.
10. Marginal Adaptation of CAD/CAM All-Ceramic Crowns Made by Different Impression Methods: A
Literature Review.
Memari Y, Mohajerfar M, Armin A, Kamalian F, Rezayani V, Beyabanaki E. J Prosthodont.
2019 Feb;28(2):e536-e544.
11. Complete-arch accuracy of intraoral scanners.
Treesh JC, Liacouras PC, Taft RM, Brooks DI, Raiciulescu S, Ellert DO, Grant GT, Ye L. J Prosthet Dent.
2018 Sep;120(3):382-388.
12. Digital intraoral scanning technique for edentulous jaws.
Fang JH, An X, Jeong SM, Choi BH. J Prosthet Dent. 2018 May;119(5):733-735.
13. Learning curve of digital intraoral scanning - an in vivo study.
Róth I, Czigola A, Joós-Kovács GL, Dalos M, Hermann P, Borbély J. BMC Oral Health.
2020 Oct 19;20(1):287.

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