Digital Workflow for Full-Arch Implant Restorations: A Case Report

By Dr Jonathan Michael

Abstract 

This case report discusses the comprehensive treatment of a 45-year-old patient, referred to as Erica, who presented with failing dentition due to previous extensive restorative work. The patient elected to proceed with full-arch implant-supported restorations after exploring various treatment options, including new crown and bridge work and bone grafting. The treatment plan was complicated by limited bone quantity in the maxilla, collapsed vertical dimension, and mandibular asymmetry. Utilising advanced digital protocols, including CBCT radiography, intra-oral scanning, and photogrammetry, the team was able to efficiently design and fabricate a temporary prosthetic, which was quickly adapted post-surgery. The final restoration was achieved using monolithic zirconia, chosen for its aesthetic properties and the high accuracy afforded by digital workflows. This approach reduced treatment time and enhanced outcomes, highlighting the benefits of integrating modern digital technologies in complex implant restorations. 

Introduction 

Erica (pseudonym) aged 45 presented seeking solutions for her failing dentition. There had been a slow decline of her natural teeth following years of past rehabilitation with crowns and bridge-work that had served her well but were no longer able to stand the test of time (Image 1; Image 2). After an interview with Erica and identifying her motivations and the outcome that she was hoping for it seemed suitable to continue our quest for information to assist the treatment planning process. CBCT radiography and dental photography were critical tools in identifying the underlying structures and lack thereof. This led us immediately into the discussion of her treatment options which ranged from complex reconstructive work with new crown and bridge work as well as bone grafting/sinus augmentation and placement of multiple implants and finally segmented prosthodontic full arch work. Additionally, the complete removal and replacement of her remaining dentition with implant supported full arch restorations was offered as an alternative treatment option. After in-depth discussion with Erica about her available options, and the pros- and cons- of each scenario, she elected to discuss and proceed with the full arch implant pathway. 

The key challenge for this case, from the surgical perspective, was the limited bone quantity and quality in the Maxilla. From the prosthodontic perspective, an incisal and midline cant, heavily collapsed vertical dimension and deep bite due to lack of posterior support as well as limited reference points, all result in a challenging starting point in re-establishing the correct rehabilitative position. Erica presented with an unusual skeletal asymmetry in the mandible adding to the difficulty in assessing the cosmetic aesthetic of the lower jaw in relation to her upper jaw. For the past few years, we have been performing full arch implant surgeries with modern digital protocols and collecting all the required data during the first appointment in anticipation of the surgery to be performed after general health checks and clearances. This protocol greatly facilitates the pre-surgical work up needed for cases like Erica’s, shortening the time and appointments needed before we are able to bring heavily compromised dentitions back to a harmonious and stable state. 

Clinical outcomes 

As mentioned above, although not entirely prohibitive, having limited reference points off which to base a smile design, is often the challenge in a case similar to Erica’s. High quality digital photography, coupled with intra-oral scanning, form the foundation on which the preliminary pre-surgical smile design is based upon. This foundation is then used as the designer and technicians’ guide for alignment of several intra-oral scans that are provided to them during and after the surgery. From the collated data, technicians are able to merge the digital pre-op design to the accurate position of the implants captured with our photogrammetry device. The link in the workflow chain which is critically under-estimated is the ‘mid-surgery’ intra-oral scan. As outlined in Fig 1., this is performed using the same soft tissue scan-bodies that are then utilised for the full arch soft tissue scan at the end of the surgery once the flap is approximated (Image 3). The ‘mid-surgery’ scan is crucial for the designers to have a STL file that presents with some of the original dentition as well as some of the newly placed implants. The two files are then able to be merged with the post-op STL of the soft tissue where all the implants in each jaw have been placed and the same soft tissue scan-bodies are also placed here for this ‘soft-tissue scan’. 

Erica’s case presented a challenge due to the limited pre-existing teeth, which meant that upon removal of some of the existing dentition necessary for the placement of the anterior implants, the design team had less reference points to align for the merging of the pre-op scans to the digital smile design to the post-op scan file (Image 3). Following this stage the remaining teeth are then extracted and the final implant was placed allowing the implant positional scans to be taken. This scan is done with the photogrammetry unit which allows for quick, consistent and accurate scanning to be performed after which the suturing occurs for the completion of the surgery (Image 5). This structured digital workflow facilitates the fabrication of a printed try-in prosthetic within a few hours of the completion of the surgery and allows the delivery of an initial set of teeth either the same or next day following this type of surgery.

The quickly fabricated try-in/temporary prosthetic affords the opportunity for easy modifications, both cosmetically and functionally, in attempts to find a new stable occlusion for Erica as well as identify any new cosmetic concerns that may occur. Generally, we will allow the process of osseointegration to continue, hopefully uneventfully, for three-months (Pandey et al., 2022). After three months we then reviewed Erica to confirm the healing process, removed the temporary prosthetic for the first time which allowed us to recapture the implant positions for a second time with the photogrammetry device as can be seen in Image 5. This process allows for the fabrication of a completely redesigned, improved and functionally more stable/strong set of full arch prosthetics. Our general protocol for final full-arch restoration is titanium reinforced prosthetics. However, with all types of full arch prosthesis there are pros and cons; the methods of positional capture of the implants can vary the ideal choice for each case as a passive fit of the final prosthetic is the ultimate goal (Wulfman et al., 2020). Some materials are more forgiving than others with this regard, offering some minor degree of flexibility whilst still being rigid enough for long term stability of the prosthetic, multi-unit abutments (MUAs), and the implants (Jivraj, S., Rawal, S., 2023). 

Three main methods can be considered in the positional capture of implants for full arch scanning that involves cross-arch scanning and cross-arch splinting of implants; analogue impression techniques, intra-oral scanning using standard, or modified scanbodies and photogrammetry (Ma et al., 2021; Revilla-León et al., 2020; Rutkūnas et al., 2023). With regards to the accuracy of each identified technique above, there is much debate in the literature with new studies and techniques emerging frequently. 

Currently, the technology of photogrammetry is superior to all other methods in the ability to deliver a prosthesis with the highest level of passivity (Lie & Jemt, 1994; Penarrocha-Oltra et al., 2017) (Image 5). A higher level of passivity allows the clinician to be able to offer a wider range of prosthetics for full arch restorations that traditionally may have presented with issues, both short- and long-term. The most notable of these materials is monolithic zirconia (De Angelis et al., 2024). Whilst relatively recent as a material of choice by some clinicians for full arch work, the lack of any flexibility of this material make it a challenging choice for a direct-to-abutment solution if impressions or intra-oral scans are the positional capture methods used. With no ti-bases, ti-bars and/or cement to offer forgiveness, the highest accuracy is essential for us to have selected monolithic zirconia direct to MUA for Erica (Image 6; Image 7). The advantages specifically for Erica was reduced turnaround time in the fabrication of her prosthetics, a more simplistic workflow and manufacturing, as well as a reduced cost overall of her treatment all whilst maintaining the high level of aesthetic output that zirconia provides (De Angelis et al., 2024). It must be noted, that with prosthetics that are direct to MUA; whether it is a printed resin, a milled PMMA or milled zirconia, as can be seen in Image 6 and Image 7, special screws are necessary for securing these prosthesis. There are few available in the current dental market; the Powerball screws, the Rosen screws, and the LA-Vis/Vortex screws. 

Concluding thoughts 

The surgical and prosthetic considerations for full arch implant therapy are numerous. From the prosthetic perspective, a few considerations are quite critical in the decision making process. The final choice of material is one of these key factors, thus ultimately determining the level of accuracy needed during the implant position capture phase. With the rise of technology in the field of implantology, previously considered niche devices and techniques are becoming more accessible and affordable, allowing the clinician to be able to choose from a wider range of restorative options without compromise to the final clinical outcome. 

In Erica’s case we were fortunate enough to have a photogrammetry device which was able to capture our implant MUA positions to a high level of accuracy as seen in the last two photographs within Image 5. The result is greater flexibility of choice for the selection of final restorative materials. Despite this, patient factors (such as parafunction, maxilla/mandible being treated, aesthetic demands/expectation, and number of implants planned) do influence the clinician’s choice irrespective of whether or not the scan was accurate or not. 

With these surgical and prosthetic considerations discussed above, we were able to recommend a monolithic zirconia upper and lower set of prosthetics, as seen in Image 6, 7 and 8, as well as understanding the benefits but also limitations of our choice. Erica began this journey with few functional teeth remaining, and after a few well planned appointments left us with an aesthetic and functional set of teeth that will hopefully stand the test of time for many years to come. 

Digital workflows now allow us to have a fairly simplified method with which we are able to achieve predictable and efficient treatment compared to methods of the past. Understanding the tools that are available to the clinician (whether it be photogrammetry or other forms of scanning) as well as having a variety of 

techniques and equipment will ultimately open up the potential for treatment of a variety of cases with more ease and calculation. In doing so, we reduce both the chair time for the patient as well as curating a reliable and long-lasting outcome. Some equipment may not be readily available to some clinicians who do not perform these procedures often enough to justify the initial outlay. However, an exploration of more affordable alternatives that allow the digital workflow detailed above to be utilised certainly exist and most will achieve clinically comparable outcomes that a clinician can be confident in providing to their patients as a high standard of care. 

References 

• De Angelis, N., De Lorenzi, M., Presicci, F. et al. The Use of Full-Contour Zirconia for Full-Arch Implant-Supported Rehabilitations—A Narrative Review. Curr Oral Health Rep 11, 8–14 (2024). https://doi.org/10.1007/s40496-024-00364-5 
• Jivraj, S., Rawal, S. (2023). Material Considerations for Full-Arch Implant-Supported Restorations. In: Jivraj, S. (eds) Graftless Solutions for the Edentulous Patient. BDJ Clinician’s Guides. Springer, Cham. https://doi.org/10.1007/978-3-031-32847-3_13 
• Lie, A., & Jemt, T. (1994). Photogrammetric measurements of implant positions. Description of a technique to determine the fit between implants and superstructures. Clinical Oral Implants Research, 5(1), 30–36. https://doi.org/10.1034/j.1600-0501.1994.050104.x 
• Ma, B., Yue, X., Sun, Y., & et al. (2021). Accuracy of photogrammetry, intraoral scanning, and conventional impression techniques for complete-arch implant rehabilitation: An in vitro comparative study. BMC Oral Health, 21, 636. https://doi.org/10.1186/s12903-021-02005-0 
• Pandey, C., Rokaya, D., and Bhattarai, B.P. (2022). Contemporary Concepts in Osseointegration of Dental Implants: A Review. Biomed Res Int., 6170452. doi: 10.1155/2022/6170452. 
• Revilla-León, M., Att, W., Özcan, M., & Rubenstein, J. (2020). Comparison of conventional, photogrammetry, and intraoral scanning accuracy of complete-arch implant impression procedures evaluated with a coordinate measuring machine. Journal of Prosthetic Dentistry, 125(1), 96-103. https://doi.org/10.1016/j.prosdent.2020.03.005. 
• Rutkūnas, V., Gedrimienė, A., Mischitz, I., Mijiritsky, E., & Huber, S. (2023). EPA consensus project paper: Accuracy of photogrammetry devices, intraoral scanners, and conventional techniques for the full-arch implant impressions: A systematic review. European Journal of Prosthodontics and Restorative Dentistry. Advance online publication. https://doi.org/10.1922/EJPRD_2481Rutkunas12. 
• Wulfman, C., Naveau, A., & Rignon-Bret, C. (2020). Digital scanning for complete-arch implant-supported restorations: A systematic review. Journal of Prosthetic Dentistry, 124(2), 161-167. https://doi.org/10.1016/j.prosdent.2019.06.014