Utilizing Intraoral Scanning and Digital Design for Implant-Based Overdentures

An excellent example of the benefits of digital dentures can be found in the case of a patient who presented to the author's denture clinic with a loose-fitting maxillary denture. After extraction of her maxillary dentition a year earlier, she had had a provisional denture made by another practice, but had not worn it due to retention complaints (Figure 1). After a consultation, the denturist decided, in collaboration with the dental surgeon, to place four implants in the maxilla. This was based upon the patient's desire to wear a prosthesis with an open palate and with the maximum retention that could be achieved. A healthy natural dentition was present in the lower arch.

Treatment Plan

Due to the expressed wishes of the patient, the restorative team decided to place four soft tissue-level Straumann implants in positions No. 13, 16, 23, and 26. No additional bone augmentation was required due to the sufficient presence of bone density in the upper arch. Two separate bars with an extension were chosen for maximum retention and stability of the prosthesis. A superstructure was designed to be fabricated over these bars. Then, the prosthesis would be milled from a monolithic base and teeth material.

To achieve optimal esthetics, the denturist planned to utilize digital smile design software, a smile library, and 3D face scanning.

Treatment Workflow and Laboratory Workflow

After the placement of the four implants and an osseointegration period of 3 months—the author sometimes allows 4 months, but the condition of this patient's bone was sufficient for loading after 3—the design of the denture could be started.

During the first consultation, the team created a portrait photo and a smile design in the design software (3Shape Smile Design, 3Shape) together with the patient (Figure 2). With the help of Fabulous Smiles, a book by Przemek Seweryniak and Kate Brantvik, a choice was made for a beautiful new smile. In addition, a 3D face scan was taken with an iPad Pro and face scanning software (Dental Pro, Bellus3D). Subsequently, an intraoral scan (TRIOS, 3Shape) was made of the maxillary and mandibular arches (Figure 3), followed by a scan with four Straumann scan flags (Figure 4). Because the patient was not wearing a prosthesis, there was no occlusal reference. The denturist measured the resting position and removed the freeway space, and then ground the scan flags—which are disposable and intended for single-use—until good contact was established with the antagonist at the correct vertical dimension of occlusion to record the interocclusal scan.

In the design software, the denturist first designed the denture based on the intraoral scans. The 3D face scan was incorporated and aligned with the lower dentition (Figure 5 and Figure 6). The chosen smile from Fabulous Smiles was utilized. To give the patient an idea of the final result, a try-in denture was 3D printed with try-in material (Figure 7 and Figure 8) (NextDent Try-In, NextDent).

The denturist then created the order for the design of both bars, adding the prosthesis as an additional scan as a reference for the position of the bars (Figure 9). By utilizing the software's "Copy and Append CAD Design to Preparation scan" workflow, the team was able to use the scan with the bars when designing the framework in the RPD workflow (Figure 10). Finally, they added the scan with the bars and the framework back to the order with the denture design to create the exact space for the basal side of the prosthesis for the framework and the bars.

The RPD was printed in casting material (Figure 11 and Figure 12) (NextDent Cast, NextDent) and converted into metal. The bars were milled by Straumann, and a model was printed with four replaceable Straumann analogs (Figure 13 and Figure 14). The arch and base were milled from base and teeth material (Ivotion, Ivoclar Vivadent).

The bars with matrices and the framework were placed on the printed model and separated with petroleum jelly (Figure 15 and Figure 16), and the milled prosthesis was connected to the matrices and the framework by means of autopolymerizing acrylic resin (Figure 17 through Figure 19).

After three appointments, the bars with the denture could be placed on the implants (Figure 20 and Figure 21), and after a year without wearing any denture, the patient had a fantastic smile again (Figure 22 through Figure 25).

Discussion

Clinically, utilizing an intraoral scanner allowed the restorative team to provide greater comfort for the patient. Additionally, the use of smile design and 3D face scanning provided a very predictable esthetic result. The final fit of the bars and denture were incredible due to the precision of the digital workflow.

For the patient, three appointments were saved through the use of the intraoral scanner and design software. Also, discussing her esthetic wishes with the smile design tool ensured a predictable end result and provided the ability for her to have much more involvement in the manufacture of the denture.

Normally, this type of case would have been intense and time-consuming for all parties involved. By collecting all the information during the first consultation and combining different options in the design, the restorative team was able to save at least 50% of its time on the clinical and laboratory work.

The successful use of an intraoral scanner in combination with a fully implanted prosthesis offers several advantages, including the clear communication to the patient, the involvement of the patient in the treatment, the reduction of the number of appointments, and the large time savings both clinically and in the laboratory.

The use of an intraoral scanner for edentulous patients does require some experience on the part of the user. Certainly, scanning multiple scan abutments in the same arch remains a task for which accuracy in the scan strategy is essential. When several steps are combined in the design software, different parts of the denture can be fabricated externally and joined together in the final phase with a perfect fit.

The author's opinion is that scanning of edentulous patients and the use of digital design for the manufacture of both implant-based and conventional prostheses will increasingly become the standard in daily practice.

About the Author

Germen Versteeg
Owner
DTL Mediaan and
Denticien
Heerhugowaard, Netherlands