Many digital workflows have been utilized in the past few years in the acquisition of implant positions for full arch implant positions intraoperatively and postoperatively. The goal of the different workflows is to offer speed, precision, and predictability. This study outlines the steps for an innovative fully digital full arch workflow that ensures predictable and fast outcomes using digital tools available in most dental implant centers.
Key points
- •
This Digital full arch workflow integrates advanced digital tools to streamline complex dental implant procedures.
- •
The scanning markers serve as radiopaque healing caps, facilitating the alignment of preoperative and postoperative cone beam computed tomography (CBCT) digital imaging and communications in medicine data.
- •
Photogrammetry systems capture precise implant positions for accurate prosthesis fabrication.
- •
Mobile intraoperative CBCT units, like the Xoran’s ultra-compact, mobile CT scanner (XCAT) by Xoran (Ann Arbor, MI) or Planmeca (Hoffman Estates, IL), facilitate capturing CBCT scans during surgery.
Introduction
The accuracy of full arch impressions for implant supported restorations in dentistry is crucial for ensuring the proper fit and function of dental prosthetics. Several factors influence the accuracy of these impressions, including the materials used, the technique employed, and the experience of the practitioner. The treatment of complex implant cases has evolved significantly with the advent of digital technology. This workflow represents a cutting-edge approach that leverages these advancements to achieve predictable outcomes. This study outlines the fully digital full arch workflow, detailing the steps involved, the equipment and materials used, and the advantages of this method in managing complex implant cases.
Discussion
The workflow represents a significant advancement in the treatment of complex implant cases. By integrating digital planning, precise surgical execution, and advanced prosthetic fabrication, this workflow addresses many of the challenges traditionally associated with implant dentistry. This workflow was created by Drs Mounir Iskandar, Bhavesh Bhakta, Ola Al Hatem, and esteemed dental technician Jeffry Tobon. It has been 2 years since implementing this workflow with over 500 successful cases delivered up to date. The concept was to find a way to align and properly mount preoperative, intraoperative, and postoperative scans. This has been a challenge for many years and many workflows have been used like fiducial markers, which are small fixation screws to be installed in specific bone sites to create landmarks; however, there were still some inaccuracies encountered. In addition, the increase in morbidity and the potential movement of these markers during surgery posed an issue to the operator. Through the integration of cone beam computed tomography (CBCT) data, photogrammetry files, and iOS scan data, this workflow provides a unique, precise, and predictable result to the full arch clinician, minimizing troubleshooting and remakes during the process.
Summary
This protocol will outline the establishment and merge of the occlusal vertical dimension and centric relation (CR) of the patient using segmented CBCT digital imaging and communications in medicine (DICOM) data preoperatively and postoperatively with the postoperative intraoral soft tissue scans and the implant positions acquired via photogrammetry. It outlines a unique and innovative protocol that minimizes guess work and provides predictable and precise results, saving both the clinician and the patient chairside time and money. With several options portrayed, the clinician may select the best fit for their practice.
Assessment and determination of patient’s centric relation for bite registration
It has been the consensus that recording the CR position of a patient in need of full mouth reconstruction is crucial for ensuring proper occlusion and prosthetic treatments. CR is a reproducible reference position, which can be utilized for diagnostic and restorative procedures with substantial historic and scientific evidence to support that premise. It stands for the maxillomandibular relationship whereby the condyles articulate with the thinnest avascular portion of their respective discs with the complex in the anterosuperior position against the shape of the articular eminence.
Regardless of the methods utilized, each has its own advantages and may be chosen based on the specific clinical situation, the dentist’s preference, and the patient’s comfort. Some examples include bimanual manipulation, chin-point guidance, free-closure, lucia jig, leaf gauge, anterior deprogrammer, electronic jaw tracking devices, gothic arch tracers, and other methods. In this technique, a simple and repeatable method of locating and recording centric relation contact position (CRCP) is with the use of a leaf gauge. This device is made up of around 50 flexible mylar strips fastened together, with each leaf thickness measuring at about 0.1 mm, numbered in order to provide an approximate record of the vertical dimension opened between the incisors.
More recent studies suggested the use of novel jaw-tracking systems that integrate into digital prosthetic workflows, such as (Modjaw, Villeurbanne, France). This system proved superiority in terms of accuracy over other industrial scanners and traditional methods. In addition, computerized occlusal analysis systems such as (Occlusense, Bausch – Laval, Canada), and (T-scan Novus, Tekscan – Norwood, MA) provide a reliable method to measure the occlusal contact areas (OCAs) at maximum bite force. Nevertheless, conventional occlusal registration methods still provide the highest validity and reliability for measuring OCA.
Surgical and digital workflow
Presurgical Protocol
Preoperative visit #1
- 1.
Establishment of the CR and vertical dimension of occlusion (VDO) is the first and most crucial step. The majority of the smile design esthetic parameters is established at this stage.
- a.
If the patient is dentate, and there is a definitive posterior stop, the CBCT is taken at the current vertical ( Fig. 1 ). If the VDO needs to be increased, it can be opened using a leaf gauge, if needed in CR.
Fig. 1 Segmented preoperative CBCT. - b.
If the patient is partially edentulous or edentulous in one or both jaws, occlusal rims and records are need to be fabricated to re-establish anterior esthetics with a definitive posterior stop and occlusal relationship at the desired vertical dimension. If the patient has existing dentures at the desired CR, the dentures will need to be relined with a wash impression to ensure the intaglio captures the anatomy of the ridges for an easier merge process to the intraoral scan (IOS) of the tissue.
- a.
- 2.
An IOS is required to capture the anatomy of the teeth and soft tissues:
- a.
If the patient is dentate or partially edentulous, the IOS is captured with adequate amount of the vestibule for virtual tissue and bone reduction.
- b.
If the patient is edentulous, 2 sets of IOSs are needed: the first one is an IOS of the edentulous tissues. The second is a scan of the intaglio and cameo surfaces of dentures/occlusal rims with radiopaque radiographic markers. Once a stable CR record is obtained, at least 3 markers are needed buccally and lingually, this will facilitate the alignment process in the digital smile design software and guarantee a seamless merge. Typically, fiducial markers like Scaneez (Suremark – Mesa, AZ), titanium, or composite markers can be used. Here composite is used and light cured with a light-emitting diode light cure ( Fig. 2 A–D ).
Fig. 2 ( A–D ) Showing the relined existing dentures ( A, B ) or record bases ( C, D ) with radiopaque composite markers.
- a.
- 3.
A CBCT is now taken at the desired CR ( Fig. 3 ).
- a.
If the patient is dentate or partially edentulous, the CBCT is captured with the teeth at the desired vertical dimension. The teeth will serve as radiographic markers for the smile design merge process in the next step.
- b.
If the patient is edentulous, the occlusal rims/relined dentures will be captured at the desired CR with the radiopaque fiducial markers.
Fig. 3 This workflow can be utilized in all scenarios; edentulous, partially dentate, and fully dentate patients. - a.
CBCT offers several benefits for full arch bite registration. These benefits make CBCT a valuable tool in achieving fast, efficient, convenient, precise, and reliable full arch bite registrations through visualizing the entire bony landmarks of the skull. In addition, bypassing common bite registration errors such as incorrect impressions and material distortion, eliminating the need for multiple steps and materials. The clear and detailed files from the CBCT can be used in the CAD system to design and fabricate restorations and be easily shared among dental professionals and laboratories. The field of view (FOV) of the 3 dimensional (3D) radiography unit should allow for capturing sufficient skull anatomy for accurate data merge. In this study, the Planmeca ProMax 3D Mid is being used in this scenario, and it combines high-quality 3D imaging and advanced large FOV dental cone beam in a variety of sizes ranging from 10 × 13 cm 2 (about 5.12 in 2 ) up to 17 × 20 cm 2 supporting a wide range of clinical options.
- 4.
Photos are required for the establishment of incisal edge position, buccal corridor, and smile line of the future prosthetic: a “Duchenne/exaggerated” smile photo is required as this can provide critical information regarding the smile line for the clinician to reduce the proper amount of bone. A great tip is to make the patient smile and squint to see how high their lip goes and capture this information. Asking the patient to close their eyes for this specific photo is extremely helpful, as patients are often conscious about the way their teeth look preoperatively. ,
Additionally, a social smile, repose, and profile photos are preferred to deliver adequate information to the digital designer. A facial scan is helpful and recommended for facial landmarks recognition and overall better case presentation. Communication with the patient and setting expectations is crucial at this stage, it is recommended to inquire about patient’s specific requests for their smile design to incorporate all requests into the smile design and discuss at the next visit.
The advent of photogrammetry
Photogrammetry is increasingly used in dentistry, particularly for capturing detailed and accurate full arch implant positions. Photogrammetry systems exhibited superior accuracy to both intraoral scanners and conventional impression technique. The accuracy of photogrammetry in this context typically falls within 20 μm. It offers several benefits when applied to full arch dental restorations, including significant advantages in terms of accuracy, patient and operator comfort, efficiency, speed, and integration into digital workflows for full arch dental restorations. It allows for easier electronic storage for future purposes as well as more convenient sharing of data files among professionals and technicians. , An accurate and sealed fit of fixed full arch implant supported restorations is very important in preventing microleakages and accumulation of bacteria. An accurately and passively fitting prosthesis is thus extremely important in preventing perimucositis and peri-implantitis. For screw-retained implant level restorations, typically a marginal gap discrepancy from 25 to 50 μm is acceptable. However, in full arch implant supported restorations, where the prosthesis is designed at abutment level, the microgap tolerance for a passive restoration varies from 50 to 100 μm.
Minor limitations arise usually from using photogrammetry units, most notably the need for a separate soft tissue scan with an intraoral digital scanner due to the lack of soft tissue reproduction with photogrammetry. Another limitation is when implants are at greater proximity or converge, the scanning can be done in separate steps, by keeping at least 1 to 3 scan bodies already registered in the first step.
Data alignment and smile design stage
The preoperative records are aligned at this stage. First, the CBCT DICOM data are segmented into a Standard Triangle Language (STL) format. CBCT provides detailed 3D images of dental structures, including teeth and bony landmarks. Segmentation helps in isolating these structures, allowing for precise diagnosis and effective treatment planning. In addition, segmentation of CBCT data allows for seamless integration into Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) systems.
Some CBCT machines could convert DICOM to STL when exporting data files, such as Planmeca using the Romexis (Hoffman Estates, IL) software.
The preoperative IOS is merged to the patient’s segmented occlusion CBCT at the desired VDO and occlusion ( Fig. 4 ). Next, the smile design digital diagnostic wax-up is constructed at that vertical, using the patient’s 2 dimensional photos as a reference for the midline, smile line, transition zone, buccal corridors, and other esthetic parameters. Alternatively, a 3D scan of the patient’s face may be utilized. During this preoperative stage, it is crucial to relay to the digital designer the desired smile design outcome, including the proper anterior teeth esthetics, correction for any occlusal cant, teeth size proportions, proper midline, incisal edge, and buccal corridor. Proper overjet, overbite, incisal flare and lip support are equally important in determining the proper position, angulation, and orientation of the future teeth.
Intraoral scanners can vary in the speed of scanning, scanning patterns, size of the IOS scanning tip, and other factors may affect the accuracy and precision of scanning results.
Because all the STL files are being merged to the STL of the desired vertical occlusion obtained of the bite CBCT, this will minimize intraoral scanning discrepancies resulting from inaccurate stitching of 3D images when using an occlusal registration obtained from intraoral scanners. Studies suggest that intraoral scanners may exhibit clinically significant errors in reproducing the interocclusal relationships. Not many in vivo studies have explored bite registration with intraoral scanners by obtaining and comparing different digital bite records by different scanners or by comparing to a control conventional polyvinyl siloxane record. Many factors may influence the accuracy of bite registration with intraoral scanners, such as optical characteristics of scanned subjects in in vitro studies and the oral environment in in vivo studies such as the presence of blood, liquids, and mist on the scanner head. In addition, because intraoral scanners utilize light to record examined surfaces, the optical properties of the material being scanned affect the results. Highly reflective materials, such as ceramics, zirconia, resin, and other metals can affect the accuracy of scans and subsequently bite registration. Moreover, due to the refractive and reflective light properties on saliva, it plays an important role in affecting the accuracy of the scanned surfaces. In patients with edentulous posterior ridges, the accuracy of the scan is affected as only the residual ridges or structures with motion frenum remain, which is inadequate for an accurate bite registration Fig. 5 demonstrates the mishaps associated with bite registration using intraoral scanners. For those reasons, intraoral digital scanners seem to work better over smaller distances and are not very reliable for cross-arch distances. On the other hand, laboratory scanners demonstrate the best trueness and precision compared to all intraoral scanners for long distances.
