Prof. János Vág
DMD, PhD, Habil
• Academic professional with extensive expertise in restorative dentistry and endodontics
• Department head and full professor at Semmelweis University of Medicine, Budapest
• Over 69 peer-reviewed publications with 694 citations and 204 scientific conference lectures
• Member of the Editorial Board of the Journal of Dentistry, Dental and Medical Problems
• Active member in international research collaborations, including the Scientific Committee of the Digital Dentistry Society and the International Association of Dental Research. American Society of Forensic Odontology and founder and first president of the Hungarian Association of Aesthetic and Restorative Dentistry
the case
the case
An acrylic fixed hybrid denture was fabricated for a 77-year-old male patient five years ago, supported by four Nobel Replace CC bone-level implants following the all-on-four concept. The patient has since reported frequent issues with detachment or fracture of the lateral incisors and the fifth tooth in the upper right quadrant (Fig. 1A, B). The denture was fabricated using conventional methods in both clinical and laboratory settings. However, it was noted that the three problematic teeth overlapped the screw-hole positions, potentially contributing to detachment due to a limited bonding surface between the acrylic teeth and the denture base.
In response to these recurrent issues, it was hypothesised that a monolithic material, where both the teeth and the base are formed in one step from the same block, could provide greater resistance to fracture. Consequently, a new implant-supported fixed denture made from monolithic full-contour zirconia material was produced using a digital workflow.
The orthopantomogram radiograph indicated no marginal bone loss or inflammation at the four implants (Fig. 2A). All implant abutments were Nobel multi-unit abutments, which were retained for the new full-arch denture (Fig. 2B).
Digital impressions were acquired using the Emerald S intraoral scanner (software version 6.3.5.9; Planmeca, Finland). Initially, a preoperative scan was conducted, encompassing the upper denture, lower dentition and bites on both sides to capture the maximal intercuspation position, reflecting the patient’s satisfaction with the existing articulation (Fig. 3).
Conical scan bodies, designed explicitly for intraoral scanning within the OXO Core system (OXO technology, Spain), were placed on the multi-unit abutments and secured manually (Fig. 4A, B). Then, the scan bodies and surrounding mucosa were intraorally scanned using the Emerald S intraoral scanner. The flagged scan bodies, identified with unique dot labels, were then affixed to the implants (Fig. 4C) and scanned via extraoral photogrammetric technology using the OXO Core system (Fig. 4D). This method ensures the precise determination of implant positions since the OXO technology reportedly has a 5 µm accuracy in capturing implant locations. Additionally, the software automatically converted the flagged scan bodies in the OXO Core scan to conical scan bodies (Fig. 4E).
“This method ensures the precise determination of implant positions since the OXO technology reportedly has a 5 µm accuracy in capturing implant locations.”
Subsequent procedures were performed using the same dental CAD software (3Shape Dental System, version 2021-1 2.21.2.2; Denmark). A merged virtual dental model was generated using the conical scan bodies, intraoral scan and photogrammetric mesh (Fig. 5A). The mean surface deviation between the scan bodies was measured as 64.2 µm using the Zeiss Inspect 3D metrology software (Zeiss GmBh, Germany; Fig. 5B). The implant positions were defined using the OXO scan, while the mucosa was defined using the intraoral scan. The occlusion and bite registration from the preoperative scan were superimposed onto the merged model to transfer the occlusion within the dental CAD software.
The framework, designed in the 3Shape Dental System, considered the previous occlusion and the final material, full-contour zirconium (Everest Zirconia Multilayer PT; UNC International, South Korea). The gingiva was fabricated from a gingiva ceramic system (MiYO Pink Ssystem; Jensen Dental GmbH, Germany) using merlot, trans lumin, trans garnet, and flamingo colours. Then, the manufactured denture was placed on a 3D-printed model with an implant replica to identify potential milling errors (Fig. 6A). The prosthesis was placed in the oral cavity and mounted on the implants. Passive fit was evaluated using the one-screw test. Intraoral X-rays, parallel to the implant platforms, were taken for each implant after tightening the screw in the #25 implant, while the other three screws were loosely fastened (Fig. 6B). Finally, all screws were tightened to 15 Ncm torque (Fig. 6C), and the occlusion, esthetics and cleanability, particularly around the abutments, were assessed (Fig. 6D).
The screw holes were sealed with Teflon tape and light-curing composite material (Fig. 7). No occlusal adjustment was necessary. The patient remained free of complaints at the one-week and three-month follow-ups, and the prosthesis was deemed aesthetically and functionally satisfactory. The digital workflow used in this case report significantly streamlined the treatment process, reducing the need for extensive corrections and condensing the treatment into just two sessions, each lasting only one hour.
“The digital workflow used in this case report significantly streamlined the treatment process.”
NOTES
*Accuracy Test Methods
For evaluation of the accuracy, two aspects (trueness and precision) were tested respectively employing methods commonly adopted by the industry.
A gypsum dental model was scanned beforehand by an industrial grade scanner to generate a dataset as reference for trueness testing where a single, trained operator used AS 260 to scan the same model for 10 separate times to obtain datasets (all STL formatted).
The datasets were then superimposed to the reference dataset for 3D comparisons to acquire 10 average error values, the mean of which was calculated to describe the trueness.
In terms of precision measurement, pairwise comparisons between the 10 datasets were operated and the average error of each comparison was calculated to generate 45 different values, the mean of which was then used to represent precision.