Digitally Designed 3D Printed Replacement Dentures

Treatment of the full arch may involve removable prostheses, either with or without implant retention, or fixed implant-supported prostheses (ie, hybrid prosthesis). Cases in which patients express dissatisfaction with the function or esthetics of their current traditional dentures can be challenging. If the vertical dimension of occlusion (VDO) is too great or insufficient, functionality can be compromised.

Advances in technology have facilitated improvements in the planning, design, and fabrication of removable prostheses. When removable full-arch prostheses are digitally planned, the fabrication of try-in prostheses can simplify the design and fabrication of the final prostheses. Intraoral scanning has obviated the need for physical material-based impressions of the arches during certain steps in the workflow, which improves efficiency by reducing the amount of manual labor involved, especially considering that the impressions do not need to be cast with gypsum. When intraoral scanning is combined with facial scanning, digital design software can be used to develop virtual images to allow patients to have some input into the esthetic planning. In addition, with advances in 3D printing resins, dentures can be 3D printed that are as esthetic and durable as those fabricated using traditional methods.¹

In the clinical case presented here, intraoral scanning and facial scanning were combined with 3D printing to produce try-in dentures to allow the patient to "test drive" the design before fabrication of the final prostheses.

Case Report

A 65-year-old male patient presented with full maxillary and mandibular dentures and indicated that he was dissatisfied with their function and esthetics. More specifically, he did not like how they resulted in a tilt of his smile that he felt made him look older than he was (Figure 1). An examination was performed, which revealed overclosure when his dentures were in occlusion that was related to decreased VDO. When smiling, the patient's plane of occlusion tipped to the right instead of paralleling the maxillary lip line perpendicular to his facial vertical axis. Furthermore, minimal maxillary anterior teeth resulted in an excessive presentation of the mandibular anterior teeth when the patient smiled, which looked unnatural. The patient was informed that a new set of dentures could be produced to achieve his expressed desires, and the benefits of using facial scanning to design the smile and 3D printing to fabricate the new dentures were discussed.

After the patient accepted the treatment plan, pretreatment full-face photographs of him smiling were acquired both with and without the dentures present. The images were then imported into smile design software (Trios Smile Design, 3Shape). Using the image without the dentures, virtual teeth were created in the software to design an esthetic smile (Figure 2). The outline of the virtual maxillary teeth was then transferred to the image with the current dentures in place for evaluation (Figure 3). The outlines of both arches of virtual teeth were viewed within the full face and modified as needed to complete the design (Figure 4). Even if facial scanning won't be used during treatment planning, designing the smile using pretreatment photographs is recommended. Full-face images both with and without the teeth being apparent are key components of smile design and execution of the overall treatment. Once the proposed smile design was completed, it was shown to the patient in the software alongside his current smile so that he could visualize the potential results (Figure 5). This step allows patients to provide input into the design of their new smiles, which enables clinicians to rectify any issues that will not achieve patients' expectations. In this case, the patient approved the proposed virtual smile, allowing the process to proceed.

Digital Record Capture

During this same appointment, a set of duplicate dentures was created. Beginning with the duplicate maxillary denture, a vinyl polysiloxane (VPS) tray adhesive was applied to the flanges and intaglio surface. A heavy body VPS impression material was then used to border mold the denture intraorally. Next the border molding was trimmed with a scalpel, and a wash impression was captured with light body VPS impression material (Figure 6). This process was then repeated for the duplicate mandibular denture. Once that was completed, both duplicate dentures were inserted intraorally, and a bite registration was captured with a VPS bite registration material to record the patient's current VDO (Figure 7).

After the bite was registration was captured, the duplicate dentures and interocclusal record were scanned with an intraoral scanner (TRIOS 4, 3Shape) and imported into the design software (Dental System, 3Shape) (Figure 8).² A facial scan of the patient was then obtained (Qlone Dental Pro, EyeCue Vision Technologies), ensuring that he had an open smile (Figure 9). Next, a small jig in the shape of a partial impression tray was created. It incorporated central incisors on the face with square (right central) and triangular (left central) depressions on their facial aspects to serve as reference points. The jig was loaded with impression material and positioned on the maxillary denture intraorally, and the patient was guided to occlude with it. Additional VPS impression material was then applied externally over the patient's upper lip to connect the jig to the base of his nose (Figure 10).³ This jig was pivotal in capturing a stable connection between the intraoral biocopy scan and the nose. This efficiently achieved a smooth and precise inclusion of the nose in the facial scan (Figure 11). At this time, the patient was scheduled for a try-in appointment and dismissed.

Design and Fabrication of the Try-In Dentures

In the digital design software, the scans of the jig and duplicate dentures were combined with the facial scan using the nose as the orientation point to achieve alignment (Figure 12). The first step in this process is aligning the scan of the jig/nose assembly with the scan of the upper denture. Then, the face scan is aligned to the jig using anatomical landmarks of the nose. With all of the files aligned, the design of the teeth is set up on the scanned upper and lower complete dentures. The face scan aids significantly in the overall visualization of the spatial position of the teeth during the design process. The mesh deviation among the aligned files is minimal and does not interfere with the spatial outcome of the final design.

Utilizing the designed smile, a virtual maxillary denture was designed, which was then separated in the design software into denture teeth and a denture base with positions to accommodate the teeth (Figure 13). This process was repeated for the mandibular arch (Figure 14). These files would be used to create try-in dentures to allow the patient to "test drive" the planned design to see if any functional or esthetic changes were needed before the final dentures were fabricated. The virtual denture bases and teeth were readied in the software by adding supports to them and positioning them on the build plates (Figure 15 and Figure 16).

The try-in denture bases were 3D printed (Pro 2, SprintRay) with a pink denture base resin (APEX Base, SprintRay) and the denture teeth were 3D printed with a denture tooth resin (APEX Teeth [shade A1], SprintRay). Following printing of the components, the supports were removed, and the surfaces were finished with laboratory rotary burs and polishers. Denture base resin was then placed into the sockets on the base, and the teeth were inserted into the sockets. After the excess resin was cleaned from the margins with a brush, the units were light cured to lock them to the denture base. Post-curing of the assembled try-in dentures was accomplished per the manufacturer's instructions.

When it comes to digital technology, the value is truly realized when we consider how digital processes overcome the errors associated with conventional methods. Digitally designed 3D printed prostheses are more retentive, stable, and comfortable than conventionally fabricated ones due to the accuracy of digital scanning as well as the accuracy of 3D printing, which mitigates the overall dimensional/volumetric shrinkage associated with using stone casts. Furthermore, stabilized, light-cure record bases and the availability of "full arch libraries" of tooth designs enable the development of a more accurate and balanced occlusion, which is particularly important in today's world given the lack of skilled denture technicians. In the case presented here, a denture system (Ivotion^® Denture System, Ivoclar) tooth library (Vivodent^® S DCL, Ivoclar ) was selected that would provide a natural-looking, functional, and esthetic outcome for the patient. All of these factors lead to the fabrication of try-in dentures that would enable both the patient and clinician to accurately assess the necessary aspects of the design prior to fabrication of the final dentures.

Try-In and Final Delivery

The patient presented to the office, and the try-in dentures were tried in (Figures 17 and 18). During the evaluation, it was noted that the left buccal corridor was more pronounced than the right buccal corridor, the mandibular anterior teeth demonstrated too much incisal display, and the midline needed to be shifted to the patient's left (Figure 19). After all of the needed improvements were identified, the patient was reappointed and dismissed. The necessary modifications were then made in the software to finalize the design for the fabrication of the definitive dentures. One of the advantages of the digital process is that it enables such changes to be made predictably and precisely, avoiding in many instances the need for additional try-in appointments.

Following the minor modifications to the design, the definitive dentures were fabricated using the same process and materials that were used to fabricate the try-in dentures. The patient returned, and the final dentures were inserted intraorally. He was given a mirror, and he expressed that he was happy with the result and that he felt that he now had a natural-looking smile (Figure 20).

Conclusion

It is common for patients who wear dentures to become unhappy with their esthetics. In addition, many experience functional issues related to VDO that drive them to seek new dentures. Virtual planning permits patient involvement in the esthetic aspects of denture design, and 3D printing facilitates the fabrication of trial dentures to allow the patient to "test drive" the design and incorporate any changes prior to fabrication of the final dentures. Advances in 3D printing resins have enabled the fabrication of esthetic and durable prostheses that are comparable to traditionally fabricated ones but can be created in less time, which further improves patient satisfaction.

About the Authors

Eric Kukucka, DD
President and Owner
The Denture Center
Windsor, Ontario, Canada
Vice President
Clinical Removable Prosthetics &
Design Technologies
Aspen Dental

Marcus Vinicius Ferreira, DDS, MSc, PhD
Adjunct Professor
Department of Restorative Dentistry
Federal University of Minas Gerais
Belo Horizonte, Brazil

Nelson RFA Silva, DDS, MSc, PhD
Professor
Department of Restorative Dentistry
Federal University of Minas Gerais
Belo Horizonte, Brazil

Gregori M. Kurtzman, DDS
Master
Academy of General Dentistry
Diplomate
International Congress of Oral Implantologists
Private Practice
Silver Spring, Maryland

Figures and Images

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Eric Kukucka, DD

Marcus Vinicius Ferreira, DDS, MSc, PhD

Nelson RFA Silva, DDS, MSc, PhD

Gregori M. Kurtzman, DDS

Fig. 1

Pretreatment full-face photographs with the mouth closed and smiling, respectively, of the patient with his current upper and lower full dentures, demonstrating a tilt in the occlusal plane that affected the overall esthetics.

Fig. 2

Software view of virtual teeth being placed into an image of the patient without the current dentures to design an esthetic smile.

Fig. 3

The outline of the virtual maxillary teeth was transferred to an image of the patient smiling with the current dentures in place for evaluation.

Fig. 4

Software view of the outlines of both arches of virtual teeth within the full face to facilitate final modifications to the smile design.

Fig. 5

A comparison of the patient’s smile with the current dentures (left) and his smile with the virtual dentures (right) was used to help him visualize the potential results so that he could proide input into the final design.

Fig. 6

Extraoral views of the duplicate maxillary denture, which was border molded intraorally with a heavy body VPS material, trimmed, and covered with a light body VPS material for a wash impression. This process was then repeated for the duplicate mandibular denture.

Fig. 7

Extraoral views of the duplicate maxillary and mandibular dentures after the impressions were finalized and an interocclusal record was acquired using a bite registration material.

Fig. 8

Design software views of the scanned duplicate maxillary and mandibular dentures with the bite record.

Fig. 9

The scans of the duplicate maxillary and mandibular dentures with the bite record were imported into the software and combined with a facial scan of the patient to inform the design.

Fig. 10

Extraoral views of a small jig in the shape of a partial impression tray, which was created with reference points on its central incisors, before and after it was placed intraorally over the duplicate maxillary denture, connected to the base of the patient’s nose with impression material, and digitally scanned.

Fig. 11

The jig aided in capturing a stable connection between the intraoral biocopy scan and the nose.

Fig. 12

The scans of the jig and duplicate dentures were combined with the facial scan using the nose as the orientation point to achieve alignment

Fig. 13

View of the virtual design of the new maxillary denture, which was then separated into designs of the denture teeth and the denture base for 3D printing.

Fig. 14

View of the virtual designs of the denture base and teeth for the new mandibular denture.

Fig. 15

View of the virtual denture bases for the maxillary and mandibular full dentures on the build plates with added supports.

Fig. 16

View of the virtual teeth for the maxillary and mandibular full dentures on the build plate with added supports.

Fig. 17

Full-face photograph of the patient wearing the 3D printed try-in dentures, which were used to confirm the function and esthetics and get the patient’s approval prior to fabricating the final 3D printed dentures.

Fig. 18

Right and left lateral full-face views of the 3D printed try-in dentures.

Fig. 19

Side-by-side comparison of the facial scan with the virtual design of the dentures and the full-face photograph of the patient wearing the 3D printed try-in dentures. It was noted that the left buccal corridor was more pronounced, the lower teeth demonstrated too much incisal display, and the midline needed to be shifted to the patients left.

Fig. 20

Posttreatment full-face photograph of the patient after delivery of the final 3D printed dentures demonstrating natural esthetics.

Eric Kukucka, DD

Marcus Vinicius Ferreira, DDS, MSc, PhD

Nelson RFA Silva, DDS, MSc, PhD

Gregori M. Kurtzman, DDS