Digital Implant Therapy for the Edentulous Patient

Recent advances in digital technology have streamlined the clinical steps necessary to achieve successful implant treatment of edentulous patients, with various treatment modalities emerging. The "digital clone" concept focuses on collecting extraoral and intraoral photographs, intraoral scans, and cone-beam computed tomography (CBCT) scans of the existing dentition and prosthesis to accurately transfer the patient's oral condition and maxillomandibular relationship (MMR) into a prosthetic design and implant planning software. In cases where fully edentulous arches are present, placement of radiopaque markers on the existing prosthesis is necessary before making the preliminary digital impressions and CBCT in order to obtain a correct file alignment and MMR (Figure 1 through Figure 3).¹

In such cases, a facially driven digital wax-up should be the starting point of the planning phase in the software. Understanding the different multi-unit abutment heights and angulations of the selected implant system is important to optimize the use of the available autologous bone ridge while achieving ideal position of the screw-access holes in the provisional restoration design. This may circumvent the need for invasive grafting procedures that will extend the duration of the treatment and will simplify the prosthetic design. Multiple software versions provide bone density indicators around the planned implant sites. This is important to consider when low density is found, especially in the maxilla. A drilling sequence modification in relation to the osteotomy width is suggested to achieve higher bone-to-implant contact and insertion torque values when immediate provisionalization is desired (Figure 4).²

Once the desired number of implants and positions have been determined, the surgical guide and provisional restoration are 3D-printed. If a hybrid design is needed for the provisional restoration, pink composite is manually layered over the tooth-colored printed provisional. For maxillary cases, the palatal surface of the provisional is maintained, providing support against the soft tissue to achieve accurate positioning. After try-in, the provisional in the present case was removed and the surgical guide inserted and fixated as planned (Figure 5 and Figure 6). The drilling sequence was followed, and the implants were inserted through the surgical stent for a fully guided placement.

All implants were submitted to ultraviolet (UV) irradiation or photofunctionalization prior to insertion to achieve higher hydrophilicity of the implant surface and increased interfacial bone deposition, denser cortical bone formation, and a stiffer bone connection, which is especially beneficial in the posterior maxillae where low-density bone is usually present.³ The use of UV irradiation is a simple method that facilitates osseointegration in compromised regions, allowing for faster osseointegration and delivery of the definitive prosthesis.⁴

After confirming that insertion torque values on each implant were higher than 35 Ncm², the previously planned multi-unit abutments were inserted and torqued, followed by placement of the temporary cylinders to convert the provisional into a fixed screw-retained immediate prosthesis (Figure 7). All temporary abutments were cleaned intraorally with a 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-containing universal cleaner with a mild pH value of 4.5 (Katana^™ Cleaner, Kuraray, kuraraydental.com), and the bonding surface of the 3D-printed provisional was air-particle-abraded with aluminum oxide, followed by application of a silane coupling agent (Clearfil^™ Ceramic Primer Plus, Kuraray). A composite resin cement (Panavia^™ V5, Kuraray) was used to adhere the temporary cylinders to the provisional prosthesis.⁵ A strong bonding interphase between the titanium cylinders and the 3D-printed provisional is critical to reduce micromovements and promote osseointegration (Figure 8).

The flanges and palate were removed and the intaglio surface was finished, ensuring that no concave surface would be present in order to provide a cleansable surface. The immediate prosthesis should be torqued following the manufacturer's recommendations and occlusal adjustments made to distribute occlusal contacts evenly throughout the arch (Figure 9).⁶

Use of a prototype is a novel step in the workflow whereby the main objective is to create a fixed interim prosthesis that corrects any possible esthetic and functional issues with the immediate provisional and provides a closer approximation to what the definitive prosthesis should look and function like. Utilizing advancements on intraoral scanners, multi-unit level scan posts are placed, and a digital impression is made, followed by a second digital impression of the immediately loaded prosthesis with scan analogs to record the intaglio, buccal, palatal, and occlusal surfaces (Figure 10 and Figure 11).

With this information, the new interim prosthesis can be designed with improved esthetics and function, 3D-printed, finished, and delivered to the patient 48 hours after the surgery while the patient wears the immediate prosthesis.⁷ This prototype is redesigned with a better overall thickness and intaglio surface because the fit with the titanium bases can be controlled (Figure 12 and Figure 13). Improved esthetics, phonetics, surface finish, and function provide a better experience to the patient during the osseointegration process and facilitate the design of the definitive prosthesis, as it is basically a difference in material only (Figure 14).

Three months after implant placement, a radiographical and clinical evaluation was made. The prototype was unscrewed, and all multi-unit abutments were retorqued at 30 Ncm² without any movement or pain, confirming a successful osseointegration. The definitive prosthesis was designed in two pieces: a titanium framework and a zirconia superstructure, which are adhesively bonded following the APC concept (air-abrasion, primer with MDP, composite resin cement). This design reduces the overall weight of the prosthesis in comparison to a full zirconia design (Figure 15 and Figure 16).⁸ Once the prototype was removed, healthy soft tissues around the implants were observed due to the ideal intaglio surface design and cleansable design (Figure 17).

The definitive titanium-zirconia prosthesis was inserted, and fixation screws were torqued at 20 Ncm². Screw-access holes were filled with direct composite material and the surface was polished after occlusal re-evaluation (Figure 18 and Figure 19). Because the design of the definitive prosthesis is very similar to the prototype, the patient experiences a smoother transition and adaptation period.⁹

High-quality data collection of extraoral and intraoral structures for an accurate replication of the patients' initial situation through the "digital clone" enables clinicians to execute a prosthetically driven plan for guided implant placement considering the final prosthetics. With an understanding of immediate loading principles, along with the correct use of intraoral scanners and newer digital implant components like scan posts and scan analogs, clinicians can obtain the necessary information to create a highly esthetic and functional prototype that will improve the quality of the interim prosthesis during the osseointegration period. This workflow facilitates the design and manufacture of the definitive implant-supported fixed dental prosthesis as well as the adaptation of the patient to the prosthesis.

Julian Conejo, DDS, MSc
Assistant Professor, Clinical Restorative Dentistry, and Director, Chairside CAD/CAM Dentistry, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Sergio Miravete, DDS, MSc
Private Practice, Mexico City, Mexico

Kwang Ho Jean, DDS
Director, DIOnavi Digital Center, Mexico City, Mexico

Jose M. Ayub, DDS
Visiting Scholar, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

Markus B. Blatz, DMD, PhD
Professor of Restorative Dentistry, Chair, Department of Preventive and Restorative Sciences, and Assistant Dean, Digital Innovation and Professional Development, University of Pennsylvania School of Dental Medicine, Philadelphia Pennsylvania; Editor-in-Chief, Compendium of Continuing Education in Dentistry