An Overview of Digital Workflows for Precision Impact Dentistry

Rafeeq N. Rahman, DDS; Alexander Lee, DMD; Setareh Lavasani, DMD, MS; and Tobias Boehm, DDS, PhD

ABSTRACT

Digital workflows in implant dentistry can help streamline and improve the quality of implant therapy by harnessing the power of cone beam computed tomography (CBCT), intraoral scanning, implant planning software, 3D printing and guided implant placement. This article provides an overview of the key steps and considerations for implementing digital implant dentistry for implant-supported fixed single or shortspan restorations using a static implant guide.

Key Steps

1. Take a CBCT and intraoral scan.

2. Merge the DICOM file with the STL file.

3. Do a digital wax-up of the tooth that needs to be replaced.

4. Plan the implant position in a restoratively driven manner.

5. Design the surgical guide.

6. 3D-print the surgical guide.

7. Place the implant using a guided implant surgical kit.8. Take an implant-level intraoral scan with a scan body.9. Deliver the implant restoration.

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AUTHORS

Rafeeq N. Rahman, DDS, is an assistant professor and clinic team leader at the Western University of Health Sciences College of Dental Medicine and practices general dentistry in Anaheim, California, with a strong emphasis on using digital workflows in dentistry. He is a fellow of the Academy of General Dentistry and the International Congress of Oral Implantologists. Conflict of Interest Disclosure: None reported.

Alexander Lee, DMD, is a full-time professor and coordinator of dental informatics at the Western University of Health Sciences College of Dental Medicine. He is the originator of the iFF app for formative assessment of dental students and has published extensively on student assessment and technology topics. Conflict of Interest Disclosure: None reported.

Setareh Lavasani, DMD, MS, is a full-time associate professor at the Western University of Health Sciences College of Dental Medicine. She is a board-certified oral and maxillofacial radiologist teaching oral radiology and advanced imaging and provides advanced practice oral radiology services and consultations to the dental school clinic and dentists in California. Dr. Lavasani is a diplomate of the American Board of Oral and Maxillofacial Radiology and a fellow of the Global Dental Implant Academy. Conflict of Interest Disclosure: None reported.

Tobias K. Boehm, DDS, PhD, is a full-time associate professor at Western University of Health Sciences teaching periodontics, implantology and biomedical sciences, along with research and providing clinical specialist services at the associated dental school clinic in Pomona, California. He is a diplomate of the American Board of Periodontology and a fellow of the International Congress of Oral Implantologists. Conflict of Interest Disclosure: None reported.

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Digital workflows in implant dentistry improve practice efficiency, procedure predictability and clinical outcomes. Digital implant planning aims to ensure that the implant is placed in a restoratively driven manner, while guided implant placement aims to ensure that the implant is placed exactly where it is digitally planned. Guided implant placement achieves higher accuracy and lower failure rates than freehanded or half-guided surgery because it provides a defined implant drilling and insertion path. [1–3] Implants placed in such a manner are also more apt to be restored with screw-retained restorations, which leads to easier maintenance. By digitizing data, the implant planning process is sped up, physical storage space is decreased and patient chair time is decreased [1,4,5]

Cone Beam Computed Tomography

The foundational technology that makes a digital workflow possible in implant dentistry is cone beam computed tomography (CBCT). CBCT uses a single, inexpensive, flat-panel or image intensifier radiation detector. CBCT imaging is performed using a rotating platform to which the X-ray source and detector are fixed. The X-ray source and detector rotate around the object being scanned and multiple, sequential, planar projection images are acquired in an arc of 180 degrees or greater. [6]

X-ray attenuation measurements from each machine position are then used to reconstruct a 3D dataset of the implant site, which can then be used by CBCT viewing software to display either a 3D rendering or any cross-sectional view of the implant site. [7,8] CBCT differs from computed tomography (CT) in that it uses a single X-ray source that produces a cone beam of radiation, rather than a fan beam as with CT. There is no accepted definition of when a fan beam (which is assumed to be planar) becomes a cone beam. [9]

The significantly lower cost and smaller computing power needed to analyze CBCT images compared to computed tomography made this technology accessible to the dental practice in 1999, when the first commercially available CBCT machine, the NewTom DVT 9000, was introduced in Europe. [8]

The American Academy of Oral and Maxillofacial Radiology (AAOMR) recommends that cross-sectional imaging be used for the assessment of all dental implant sites and that CBCT is the imaging method of choice for this information. 8 Once a CBCT image is taken, it is recommended that the image be interpreted by an oral and maxillofacial radiologist. The AAOMR noted that “dentists using CBCT should be held to the same standards as boardcertified oral and maxillofacial radiologists (OMFRs), just as dentists excising oral and maxillofacial lesions are held to the same standards as oral and maxillofacial surgeons. It is the responsibility of the practitioner obtaining the CBCT images to interpret the findings of the examination. Just as a pathology report accompanies a biopsy, an imaging report must accompany a CBCT scan.” [10]

A CBCT image can be obtained from a dental imaging center or by setting up a CBCT machine within the dental office. The choice for either depends on multiple factors including physical space, economic feasibility, practitioner comfort with the devices and the needs of the patient population. For those looking to purchase a machine for their office, contemporary CBCT devices have a smaller footprint than previous generations as well as higher resolution and faster image acquisition. Additionally, these CBCT machines possess scatter correction or scatter reduction methods that reduce X-ray artifacts from radiation being deflected by restorations using beam-blocking techniques [11] or mathematical corrections. [12]

Digital File Types

Digital implant planning requires two main pieces of data: a CBCT of the patient as a series of DICOM (.dcm) files and an intraoral scan of the arch as an STL (.stl) file.

A DICOM file is the standard file type for medical data, defined by the National Electrical Manufacturer’s Association (NEMA), that all CBCT machines are capable of outputting. In addition to the image data, each file contains information about the patient, acquisition date and method and the spatial location of the image data. Each DICOM file represents an image section, and the entire collection of DICOM files makes up the 3D representation of an implant site. [13] Because of the patient data associated with each DICOM file, practitioners should take care to follow HIPAA guidelines to secure them, especially when they are exported from their picture archiving and communication system (PACS).

Intraoral scans can be exported into 3D model file formats such as STL, OBJ, 3MF and more. While each format has its unique properties, the STL has become the most widely used format for 3D models because of its relatively small file size, speed of export and wide-ranging compatibility. Disadvantages of the STL file type for dentistry are that it does not contain color or scale information, meaning its units of measurement are arbitrary. Despite these drawbacks, adoption of the STL is so wide that most current dental scanning software and device manufacturers use the file type. Due to its established use in dentistry, this paper refers to 3D model files as STLs.

Intraoral Scanners

There are many intraoral scanners on the market, each with software capable of doing simple to complex dental treatments digitally. Though an in-office intraoral scanner streamlines the process, many dental labs can scan conventional models or impressions and provide an STL file for a fee. For practitioners looking to purchase an intraoral scanner, factors to consider when selecting one include:

■ Integration with other existing practice technologies: Software suites like Romexis, DTX Studio and Dolphin Imaging support intraoral scanning. If a practice is already using such a software but is not utilizing the intraoral scanning capabilities, acquiring a manufacturer-supported intraoral scanner would decrease the setup and training time.

■ Practice use case: Different scanners may be optimized for different procedures. For example, the iTero Element series of scanners would be ideal for Invisalign users due to the tight softwarehardware integration, as both are made by Align Technologies.

■ Form factor: In addition to considering an intraoral scanner’s size for a patient’s mouth, practitioners should also evaluate whether a scanner comes attached to a proprietary cart, the length and type of cable, size of cradle and device ergonomics.

■ Manufacturer support: Terms of support and its cost influence practitioner confidence and can minimize downtime.

■ Cost: New intraoral scanners cost between $9,000 to $50,000 per unit. Support packages range from free to hundreds of dollars a month.

■ User interface and experience: While some manufacturers offer a “white glove” experience where all support concerns are mitigated, others provide a “bare bones” approach that encourages the end user to create custom solutions.

Some examples of intraoral scanners include 3Shape Trios 4, Planmeca Emerald S, Align Itero Element D, Carestream Dental CS 3700 and Medit i700. The images shown in this review are from 3Shape’s Trios 3 intraoral scanner.

Intraoral Scanning

For restoratively driven implant placement, three intraoral scans are needed: an intraoral scan of the arch containing the implant site (FIGURES 1), an intraoral scan of the opposing arch and an intraoral scan of the bite (FIGURES 1). This can be used to create a virtual articulator and a digital wax-up. The digital waxup must have the proper dimensions, be in the correct occlusal plane and occlusion, and most importantly, be in the correct long-axis. Ideally the tooth should be missing in the intraoral scan. However, for immediate implant cases, the tooth to be replaced can be digitally removed using the planning software.

It is crucial that the intraoral scan is accurate, since the fit of the surgical guide and the placement of the implant depend on it. Digital impressions obtained from intraoral scanners appear to be as accurate as analog. [14–17]

Intraoral scanning accuracy can be improved with these techniques:

■ Keep the teeth dry, especially the occlusal surfaces. Scanners have difficulty differentiating between teeth and saliva.

■ Use a proper fulcrum or manufacturer-specified support.

■ Visually focus on the computer monitor and not the intraoral scanner itself.

■ Capture a few millimeters of soft tissue past gingival margins of the teeth, especially in the edentulous space where the implant will go.

■ Capture the interproximal tooth surfaces of the teeth adjacent to the edentulous space. This requires tipping the scanner head mesially or distally to capture tooth structure cervical to the height of contour.

■ More scanning does not mean more accuracy. The data should be captured completely, but efficiently. If certain areas need to be rescanned multiple times to get the data completely, there is likely an error or discrepancy somewhere in the scan, and it is best to start over.

Digital bite registrations can be improved with these techniques:

■ Make sure the patient is biting properly in their maximum intercuspal position (MIP) without moving or quivering.

■ Ensure the teeth are quite dry.

Merging the CBCT and Intraoral Scan Data

Once the CBCT DICOM and intraoral scan STL files have been created, they can be imported into the implant planning software. Many different implant planning software packages are available. Common examples are Planmeca Romexis, 3D Diagnostics 3DDX, 3Shape Implant Studio, Dentsply Sirona Simplant and BlueSkyPlan by Blue Sky Bio. Implant planning software have similar capabilities; the choice depends on the subscription model and the ease with which the software integrates into the existing hardware of a particular office. The images in this section are from BlueSkyPlan by Blue Sky Bio.

The first step is to align the DICOM data containing bone and tooth surfaces with the STL data containing tooth and soft tissue surfaces. Some software merge the two datasets automatically. Additional manual refinement can be done by shifting the model in any of three axes to better align with the CBCT image. Aligning CBCT and tooth surface data can result in higher accuracy of implant placement. 18 If the software does not align automatically, you can manually do so by merging with points (FIGURES 2). In this method, the software user must select a series of corresponding points on the model and the CBCT image, such as grooves or cusp tips, which are easily identifiable in both data sets. The software will then align the two datasets together based on the points selected.

Regardless of the alignment method, the accuracy of the alignment needs to be verified. If the models are well aligned, tooth surfaces from both the model and the CBCT should be intimately adapted on individual CBCT slices (FIGURES 3).

Once the two data sets are merged, a digital wax-up of the tooth for the implant sites can be created. This is done by inserting a tooth shape from the software and adjusting its size and position along the mesiodistal, buccolingual and apicocoronal axes (FIGURE 4). The tooth should be positioned and sized exactly as the final restoration will be because the implant will be planned according to this digital wax-up. In most programs, the digital wax-up can be locked in so that it is not inadvertently altered later in the implant planning process.

Digital Implant Planning

The implant surgeon should review the entire volume of the CBCT to get acquainted with patient-specific local anatomy and look for bone abnormalities and/or presence of any other pathology. If implants in the mandible are placed, the inferior alveolar nerve should be marked in the volume by identifying its course distal from the mental foramen. Likewise, in the maxilla, the position of unusually prominent neurovascular bundles in the bone should be marked (FIGURE 5).

The next step is to determine the appropriately sized implant from the collection of implants in the chosen implant system. The available bone for implant placement provides the possible size for an implant at a given site and often dictates which implant size can be placed. To measure available bone accurately, the sectional views must be lined up so that the buccolingual and mesiodistal sections are perpendicular to the bone surfaces and the view is centered on each implant site (FIGURE 6).

Each implant must also meet the following requirements:

■ At least 2.65 mm superior to the inferior alveolar nerve 19 and 5 mm mesial to the mental foramen. 20

■ At least 1.0 mm (platform-switched implants) to 1.5 mm (nonplatform switched implants) from the implant platform to adjacent teeth [21] and at least 3.0 mm between adjacent implant platforms. [22]

■ A 2 mm thick shield of facial bone to the facial implant surface is advised. [23]

■ Most implants with completely rough surfaces need to be placed with the implant platform flush or slightly apical to the crestal bone. Placing implants with machined collars apical to the crestal bone may result in bone loss. These requirements typically provide maximum implant dimensions for the available bone. However, available implant dimensions and restorative design considerations including desired emergence profile and support may dictate different dimensions. For example, even if a posterior maxilla implant site features a 12 mm-wide ridge allowing placement of an 8 mm-wide implant, the largest implant size available from a given manufacturer may only be 6 mm in diameter. [24] Likewise, if available bone is less than required for restorative needs, site development procedures such as ridge augmentation need to be done. [25] Short implants (less than 10 mm length) may help overcome limitations in available bone height, although concerns have been raised about possible mechanical disadvantages from a poor crown:implant ratio. Yet, crown:implant ratio does not seem to be associated with enhanced peri-implant bone loss and may not affect implant survival. 26,27 Small diameter implants (less than 3.5 mm) may have similar bone loss and survival rates than standard diameter implants [28] when placed in atrophic ridges, but may have higher complication rates and potential for fracture if placed in posterior areas. [29,30]

Once the appropriately sized implant has been selected, it typically needs to be placed at the center of the restoration for posterior teeth and canines and palatal to the restoration center for incisors. The goal for incisors is to place the implant so that the facial platform edge is just lingual to the planned incisal edge to allow for a screw-retained restoration and allow for easier development of the facial emergence profile. The overall goal for implant placement is to achieve an implant axis perpendicular to the occlusal table of the restoration to minimize off-axis loading and avoid prosthetic complications [31] (FIGURE 7).

It is possible that the position of the virtual implant dictated by the restoration results in facial perforation of the cortex at the implant apex. In this case, the choice is either to accept a more difficult restoration by adjusting the implant position or to address the perforation with grafting during implant placement. The decision depends on which method can be more predictably achieved for a given case.

If the appropriate virtual implant length results in perforation of the sinus, appropriate sinus augmentation procedures should be planned along with implant placement. If the existing bone width is not sufficient for implant placement, ridge augmentation or alternatives to implant therapy should be considered. When working as a team, the implant surgeon and restorative dentist must agree on the desired implant position.

A benefit of digital implant planning is the ability to try out different implant sizes and positions and quickly see the outcome in terms of screw-hole position and relationship to the restoration (FIGURES 8).

Guided Surgery Kits

Guided implant placement requires the use of specialized guided surgery kits. The design of the kits varies by manufacturer, but in general the kits can have either guided drills (FIGURE 9) or conventional drills (FIGURE 10) with a series of adapter keys.

With the latter, the keys engage the guide tube, and each key has a hole in the center, of varying diameter, which allows the conventional drill to pass through. Using the key during the osteotomy can be challenging because it needs to be held in place inside the guide tube. The advantage of these systems is that the cost to transition to guided surgery is lower as they make use of the conventional drill kit.

With guided drill kits, every drill has a guiding surface built into it. These kits are much simpler to use than keys because the drill goes directly into the guide. These kits often come with guided implant carriers that for allow fully guided placement. The disadvantage of these systems is the higher cost.

Designing the Guide

Once the implant position is finalized, the next step is to design the surgical guide. Each implant manufacturer’s guided implant surgical kit is different and has its own parameters to create the guide tube (FIGURES 11), which directs the guiding portion of the drill. The following are the parameters needed:

■ Diameter: This is the inner diameter of the guide tube. It should be as narrow as possible to still allow the guiding portion of the drill to pass through yet reduce lateral movements of the drills. 32,33 Some systems have a separate drill for each step with a single diameter guiding portion that does not change. Other systems use a key system where the drill diameters are different, so a key is needed as an adapter between the drill and the guide. This controls the implant placement in the buccolingual and mesiodistal axes.

■ Offset: This determines the position of the top of the guide tube. It is the vertical distance between the stopper on the drill and the platform of the implant. This controls the implant placement in the apicocoronal axis.

■ Height: This determines the position of the bottom of the guide tube. It is the height of the guide tube from the top to the tissue level. This should be as tall as possible to minimize lateral movements of the drills. [34]

Once this information is programmed into the software, the extensions of the guide need to be marked. In dentate areas, it is best to go just past the height of contour to allow retention of the guide during implant placement (FIGURES 11). In edentulous areas where implants will be placed, it is best to go 3 mm to 4 mm past the neighboring gingival zenith to help retract the elevated tissue during implant placement using a flap approach. Adding windows at selected cusps and incisal edges is helpful, as it allows verification of complete guide seating during implant placement (FIGURE 12).

Once satisfied with the guide, the guide can be exported as an STL file (FIGURE 12) to be fabricated in a 3D printing machine. A benefit of the BlueSkyPlan software is that digital implant planning is free and a cost is only incurred once the STL file is exported.

Surgical Guide Fabrication

The STL file from the planning process can be used to print a guide in office with a 3D printer capable of printing surgical guides with resins approved by the FDA for intraoral use or to send to a dental laboratory for guide fabrication. Some implant systems require a metal sleeve to be inserted into the guide tube after fabrication, while others are sleeveless (FIGURE 13).

3D Printing

3D printers work through a process known as additive manufacturing: 3D models are cut into many digital layers and then built up in the printer layer by layer. The quality of the object improves with thinner layers. This is akin to CT scanning software that creates a 3D image of part of the body by combining slices together. While many 3D printers exist, the most common printers in dentistry utilize resin as their material. Two of the common methods for 3D resin printing are:

■ Material extrusion (FDM): This method involves extruding a plastic filament material through a heated nozzle. The printer extrudes the material back and forth along a predetermined path to create a 3D object, 35 similar to dot-matrix printers for paper (FIGURE 14). This method has lower dimensional accuracy, as the thinnest layer possible is 0.5 mm. FDM printing is not recommended for dental purposes due to insufficient level of detail and the lack of FDA-approved materials.

■ Vat polymerization (SLA, DLP): This method involves using a light to cure individual layers from a vat of resin (FIGURE 15). This method has much higher dimensional accuracy, as layers can be as thin as 20 microns. 35 New technologies are being developed that can print layers as thin as 5 nanometers. This is the currently preferred method for 3D printing of dental objects. Today, resins are available for a multitude of dental purposes including dental models, surgical guides, occlusal guards, orthodontic models and indirect bonding trays, provisional crowns and even long-term objects like dentures and resin restorations. There are several 3D printers on the market today that are designed for dental use such as Formlabs Form3+, SprintRay Pro S and Whip Mix Asiga Pro 4K.

The vast 3D printer market provides dentists with innumerable options beyond those stated previously, but one selection criterium rises above the rest — selecting a 3D printer with dentistry-ready features from the manufacturer allows practitioners to efficiently and predictably print their prepared STL files. Such printers have a user-experience like milling units integrated within CAD/CAM systems, boasting solidified digital processes, lists of approved materials and dental-focused custom settings. For printers that do not have these capabilities, users may need to manually repair STL files, transfer them to the printer, orient the models, experiment with unsupported resins and set print parameters through trial and error.

Resin-based 3D-printed models require finishing steps consisting of removing support structures, washing the print, post-print curing and polishing. While finishing stations can be created from existing dental lab equipment (a fume hood, lab handpiece, curing device, glass containers, ethanol and hand tools), dedicated devices like the Elegoo Mercury or SprintRay Pro Wash/ Dry streamline the process by keeping hazardous materials contained, automating tasks like agitating a model during washing and consolidating equipment into a single device to save space.

Regardless of the type of 3D printer and finishing process used, the National Institute for Occupational Safety and Health (NIOSH) has identified three common work hazards for additive manufacturing: breathing harmful materials, skin contact with harmful materials and flammable materials. During all printing stages, NIOSH recommends proper engineering controls, administrative controls and personal protective equipment. This includes using high-efficiency particulate air (HEPA) filters, introducing safety guidelines for handling and securing volatile materials like resins and solvents and wearing respirators, gloves and safety goggles. [36]

Surgery Stage

For implant cases where the guide uses existing adjacent teeth for indexing, the guide can simply be placed on the teeth until it seats completely and does not rock. While it is possible to adjust an ill-fitting guide, it indicates an error occurred during the digital workflow, which can result in the implant not being placed in the planned location. The digital planning and guide fabrication steps should be redone with care.

The guide can be used during implant surgery for direct drilling of the osteotomy only (known as half-guided implant placement) or for both drilling the osteotomy and placing the implant through the guide (known as fully guided implant placement). 37 A fully guided approach is more accurate than the partial-guided approach, as distal deviation and angular deviations from the planned position are significantly smaller with the fully guided approach. [38]

Guided implant placement follows the same principles as freehanded implant placement regarding patient preparation, anesthesia and suturing. While the principles are similar, flap design, osteotomy and implant placement require minor modifications with the guided technique.

Patient preparation involves obtaining informed consent about risks, benefits and alternatives and an appropriate description of the procedure, medications and what to expect. A single preoperative antibiotic dose is sufficient to significantly reduce early implant failure. 39 For local anesthesia, local infiltration using buccal, crestal [40] and lingual infiltration is sufficient for most forms of implant placement.

Guided implant placement presents the opportunity for predictable flapless surgery if sufficient keratinized gingiva is present and the underlying bone anatomy allows for it. For this, a biopsy punch drill is used through the guide hole at the implant site until the drill touches bone. The guide is then removed, and the tissue plug at the implant site is removed using suitable instruments such as tissue forceps, periosteal elevators or periodontal knives.

A full thickness flap should be raised for implant placement if the procedure also requires bone removal, simultaneous ridge grafting or high case difficulty where direct visualization of the bone is needed. Suturing typically aims to limit tissue mobility and aid healing.

For the osteotomy with a conventional kit, a key specific for each drill is placed into the guide, and the drill passes through the key. For the osteotomy with a guided kit, each drill is passed directly through the guide. Each drill has a drill stop that reaches the predetermined length (the implant length + tissue thickness + guide thickness) that was programmed into the guide. The osteotomy should follow the manufacturer’s protocol using a surgical drill with high rpm, low torque, copious irrigation, low pressure and, if needed, a straight up-and-down pumping motion to prevent thermal damage to the bone.

Implant placement should also follow manufacturers’ protocols, typically using very low speed (< 20 rpm) and a defined torque (often 30 Ncm to 50 Ncm) that provides sufficient stability without inducing pressure necrosis. For maximum benefit and fully guided surgery, the implant should also be placed through the guide to minimize placement errors. If the implant is placed freehanded after using the guide for the osteotomy, angulation errors may be introduced and some of the benefits of fully guided surgery will be lost. At each osteotomy and implant placement step, the clinician must check if the placement matches what was planned and if the placement is appropriate for the given site.

Pitfalls of Using Guides

For posterior areas, using a surgical guide on a dentate patient may be difficult, as the acrylic and added implant drill length may prevent the operator from using the guide, especially in individuals with limited mouth opening.

For maximum benefit and fully guided surgery, the implant should also be placed through the guide to minimize placement errors.

While fully guided implant surgery can result in improved placement accuracy, placement errors are still possible stemming from inaccuracies in the CBCT acquisition, 3D scanning, guide planning, 3D printing, positioning of the guide during surgery and short guide sleeve length. 41 It is also possible that a clinician may need to forgo using a surgical guide as consequence of unanticipated complications encountered during surgery, such as insufficient implant stability at the planned insertion depth, closer than expected proximity to vital structures, encountering a bone dehiscence or a poorly fitting guide. 42 While low-cost 3D printers can produce acceptable guides, 43 accuracy of the guide is dependent on the manufacturing process and size of the guide, with small guides having better fit. [44]

Dynamically Guided Surgery

The previously described method using a surgical guide fitted over the adjacent teeth describes static guided surgery, which is the more common guided surgery approach. Dynamically guided implant placement was introduced to dentistry in the year 2000, where motion tracking of the patient and handpiece provides the clinician instant feedback about the planned implant position within the context of CBCT data. More recent availability of in-office CBCT machines, reduced cost and improved designs to facilitate use of these systems in a dental office have led to greater interest in this technology, as it may result in a simpler implant planning workflow. 45 Currently, two dynamically guided implant systems have received FDA 510(k) clearance and are available in the U.S. (i.e., Navident ClaroNav, X-Nav X-Guide Dynamic 3D Navigation). 46,47 With these systems, cameras mounted in the operatory record optic markers placed on the handpiece and the patient and a computer system provides the operator feedback on a screen whether the implant motor is positioned at the correct angle and position. As another approach in dynamically guided implant placement, robotics was introduced to implant dentistry in 2017 with the development of an autonomous robot implant placement system in China and FDA clearance of a robotic system that assists placement of implants. [48] The FDA-cleared system is available as the Neocis YOMI system where a handpiece is mounted on a robotic arm that provides the operator haptic feedback on the correct angulation and position. [49] Currently, this system has been developed for use in fully and partially edentulous arches, but requires sufficient teeth or bone to stably hold a splint in place. [50] A drawback of the robotic approach is that this system is still quite expensive and is still undergoing development for wider applications.

Digital Restoration

Once the implant is integrated and ready to be restored, a conventional implant-level impression can be taken to have the restoration fabricated. However, the digital workflow can continue with an intraoral scan of the implant to reap the maximum benefits from digital dentistry.

To use an intraoral scanner for an implant restoration, a scan body is required. A scan body is equivalent to the impression coping (FIGURE 16) in the conventional method. Each scan body is unique to each implant platform, as with an impression coping, so this needs to be ordered from the implant distributor prior to the intraoral scan appointment. The scan body is used in the same way as an impression coping. The healing abutment is removed, the scan body seated and hand-tightened and a radiograph taken to verify complete seating. Once fully seated, an intraoral scan is taken in lieu of an impression, taking care to capture all the notches of the scan body in detail (FIGURES 17).

The lab uses the scan body image to determine the exact implant position and to design the abutment and restoration accordingly. The lab can print a model and fabricate the restoration conventionally, or it can design and mill the restoration digitally.

Conclusion

Digital implant workflows hold the promise for dentists to plan and execute implant placement with great accuracy, reliability and predictability, leading to potentially simpler and more predictable restoration. The key requirements for implementing digital implant dentistry are to use a CBCT machine and an intraoral scanner to create a 3D model of bone, teeth and overlying soft tissue and to use this model to plan implant placement for guided surgery.

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REFERENCES

1. Gargallo-Albiol J, Barootchi S, Marques-Guasch J, et al. Fully guided versus half-guided and freehand implant placement: Systematic review and meta-analysis. Int J Oral Maxillofac Implants 2020 Nov/Dec;35(6):1159–1169. doi: 10.11607/jomi.7942.

2. Putra RH, Yoda N, Astuti ER, et al. The accuracy of implant placement with computer-guided surgery in partially edentulous patients and possible influencing factors: A systematic review and meta-analysis. J Prosthodont Res 2022 Jan 11;66(1):29–39. doi: 10.2186/jpr.JPR_D_20_00184. Epub 2021 Jan 26.

3. Abdelhay N, Prasad S, Gibson MP. Failure rates associated with guided versus non-guided dental implant placement: A systematic review and meta-analysis. BDJ Open 2021 Aug 18;7(1):31. doi: 10.1038/s41405-021-00086-1. PMCID: PMC8373900.

4. Joda T, Ferrari M, Gallucci GO, et al. Digital technology in fixed implant prosthodontics. Periodontol 2000 2017 Feb;73(1):178–192. doi: 10.1111/prd.12164.

5. Siqueira R, Galli M, Chen Z, et al. Intraoral scanning reduces procedure time and improves patient comfort in fixed prosthodontics and implant dentistry: A systematic review. Clin Oral Investig 2021;25(12):6517–6531. doi: 10.1007/s00784-021-04157-3. Epub 2021 Sep 27. PMCID: PMC8475874.

6. Arai Y. Local cone beam CT: How did it all start? Dentomaxillofac Radiol 2021 Dec 1;50(8):20210276. doi: 10.1259/dmfr.20210276. Epub 2021 Nov 9.

7. Tyndall DA, Brooks SL. Selection criteria for dental implant site imaging: A position paper of the American Academy of Oral and Maxillofacial Radiology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89(5):630–637. doi: 10.1067/moe.2000.106336.

8. Tyndall DA, Price JB, Tetradis S, et al. Position statement of the American Academy of Oral and Maxillofacial Radiology on selection criteria for the use of radiology in dental implantology with emphasis on cone beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;113(6):817–826. doi: 10.1016/j.oooo.2012.03.005.

9. Scarfe WC, Farman AG. What is cone-beam CT and how does it work? Dent Clin North Am 2008;52(4):707–730, v. doi: 10.1016/j.cden.2008.05.005.

10. Carter L, Farman AG, Geist J, et al. American Academy of Oral and Maxillofacial Radiology executive opinion statement on performing and interpreting diagnostic cone beam computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008 Oct;106(4):561–562. doi: 10.1016/j. tripleo.2008.07.007.

11. Jin JY, Ren L, Liu Q, et al. Combining scatter reduction and correction to improve image quality in cone-beam computed tomography (CBCT). Med Phys 2010 Nov;37(11):5634–5644.

12. Yang FQ, Zhang DH, Huang KD, et al. Image artifacts and noise reduction algorithm for cone-beam computed tomography with low-signal projections. J Xray Sci Technol 2018;26(2):227–240. doi: 10.3233/XST-17285.

13. National Electronics Manufacturer Association. DICOM PS3.3 2021e – Information Object Definitions. 2021. Accessed Jan. 18, 2022.

14. Papaspyridakos P, Vazouras K, Chen YW, et al. Digital vs. conventional implant impressions: A systematic review and meta-analysis. J Prosthodont 2020 Oct;29(8):660–678. doi: 10.1111/jopr.13211. Epub 2020 Jul 16.

15. Tallarico M, Xhanari E, Kim YJ, et al. Accuracy of computer-assisted template-based implant placement using conventional impression and scan model or intraoral digital impression: A randomised controlled trial with 1 year of followup. Int J Oral Implantol (Berl) 2019;12(2):197–206.

16. Zimmermann M, Ender A, Attin T, et al. Accuracy of buccal scan procedures for the registration of habitual intercuspation. Oper Dent 2018;43(6):573–580. doi: 10.2341/17-272-C. Epub 2018 Apr 9.

17. Wong V, Smith AJ, Hawkins NJ, et al. Adaptive tutorials versus web-based resources in radiology: A mixed methods comparison of efficacy and student engagement. Acad Radiol 2015;22(10):1299–1307. doi: 10.1016/j. acra.2015.07.002. Epub 2015 Aug 17.

18. Kernen F, Benic GI, Payer M, et al. Accuracy of threedimensional printed templates for guided implant placement based on matching a surface scan with CBCT. Clin Implant Dent Relat Res 2016;18(4):762–768. doi: 10.1111/ cid.12348. Epub 2015 Apr 28.

19. Hartmann A, Welte-Jzyk C, Seiler M, et al. Neurophysiological changes associated with implant placement. Clin Oral Implants Res 2017;28(5):576–581. doi: 10.1111/clr.12837. Epub 2016 Mar 22.

20. Ritter L, Neugebauer J, Mischkowski RA, et al. Evaluation of the course of the inferior alveolar nerve in the mental foramen by cone beam computed tomography. Int J Oral Maxillofac Implants 2012;27(5):1014–1021.

21. Vela X, Mendez V, Rodriguez X, et al. Crestal bone changes on platform-switched implants and adjacent teeth when the tooth-implant distance is less than 1.5 mm. Int J Periodontics Restorative Dent 2012 Apr;32(2):149–155.

22. Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the height of inter-implant bone crest. J Periodontol 2000;71(4):546–549. doi: 10.1902/jop.2000.71.4.546.

23. Merheb J, Quirynen M, Teughels W. Critical buccal bone dimensions along implants. Periodontol 2000 2014;66(1):97–105. doi: 10.1111/prd.12042.

24. ZimVie. T3 Implants. Accessed July 12, 2022. 25. Rissolo AR, Bennett J. Bone grafting and its essential role in implant dentistry. Dent Clin North Am 1998 Jan;42(1):91–116.

26. Blanes RJ. To what extent does the crown-implant ratio affect the survival and complications of implant-supported reconstructions? A systematic review. Clin Oral Implants Res 2009;20 Suppl 4:67–72. doi: 10.1111/j.1600- 0501.2009.01762.x.

27. Fathi A, Rismanchian M, Khodadadi R, et al. Does the crown-implant ratio affect the survival and complications of implant-supported prostheses? A systematic review. J Prosthet Dent 2022 Apr 22;S0022–3913(22)00175–5. doi: 10.1016/j.prosdent.2022.03.007. Online ahead of print.

28. Gonzalez-Valls G, Roca-Millan E, Cespedes-Sanchez JM, et al. Narrow diameter dental implants as an alternative treatment for atrophic alveolar ridges. Systematic review and meta-analysis. Materials (Basel) 2021;14(12). doi: 10.3390/ ma14123234.

29. Lee JS, Kim HM, Kim CS, et al. Long-term retrospective study of narrow implants for fixed dental prostheses. Clin Oral Implants Res 2013;24(8):847–852. doi: 10.1111/j.1600- 0501.2012.02472.x. Epub 2012 Apr 2.

30. Quek CE, Tan KB, Nicholls JI. Load fatigue performance of a single-tooth implant abutment system: Effect of diameter. Int J Oral Maxillofac Implants 2006;21(6):929–936.

31. Koyano K, Esaki D. Occlusion on oral implants: Current clinical guidelines. J Oral Rehabil 2015;42(2):153–161. doi: 10.1111/joor.12239. Epub 2014 Oct 6.

32. Schneider D, Schober F, Grohmann P, et al. In-vitro evaluation of the tolerance of surgical instruments in templates for computer-assisted guided implantology produced by 3-D printing. Clin Oral Implants Res 2015;26(3):320–325. doi: 10.1111/clr.12327. Epub 2014 Jan 18.

33. Koop R, Vercruyssen M, Vermeulen K, et al. Tolerance within the sleeve inserts of different surgical guides for guided implant surgery. Clin Oral Implants Res 2013;24(6):630– 634. doi: 10.1111/j.1600-0501.2012.02436.x. Epub 2012 Mar 13.

34. Tallarico M, Kim YJ, Cocchi F, et al. Accuracy of newly developed sleeve-designed templates for insertion of dental implants: A prospective multicenters clinical trial. Clin Implant Dent Relat Res 2019;21(1):108–113. doi: 10.1111/ cid.12704. Epub 2018 Dec 28.

35. All3DP. The Types of 3D Printing Technology of 2021. Accessed Jan. 22, 2022.

36. Glassford E, Dunn KL, Dunn KH, et al. 3D printings with filaments: Health and safety questions to ask. In: U.S. Department of Health and Human Services CfDCaP, National Institute for Occupational Safety and Health (NIOSH) ed. Cincinnati: NIOSH; 2020.

37. Kuhl S, Zurcher S, Mahid T, et al. Accuracy of full guided vs. half-guided implant surgery. Clin Oral Implants Res 2013;24(7):763–769. doi: 10.1111/j.1600- 0501.2012.02484.x. Epub 2012 May 3.

38. Bencharit S, Staffen A, Yeung M, et al. In vivo toothsupported implant surgical guides fabricated with desktop stereolithographic printers: Fully guided surgery is more accurate than partially guided surgery. J Oral Maxillofac Surg 2018;76(7):1431–1439. doi: 10.1016/j.joms.2018.02.010. Epub 2018 Feb 21.

39. Roca-Millan E, Estrugo-Devesa A, Merlos A, et al. Systemic antibiotic prophylaxis to reduce early implant failure: A systematic review and meta-analysis. Antibiotics (Basel) 2021;10(6). doi: 10.3390/antibiotics10060698.

40. Giffin KM. Providing intraosseous anesthesia with minimal invasion. J Am Dent Assoc 1994;125(8):1119–1121. doi: 10.14219/jada.archive.1994.0128.

41. Mistry A, Ucer C, Thompson JD, et al. 3D guided dental implant placement: Impact on surgical accuracy and collateral damage to the inferior alveolar nerve. Dent J (Basel) 2021;9(9). doi: 10.3390/dj9090099.

42. Ku JK, Lee J, Lee HJ, et al. Accuracy of dental implant placement with computer-guided surgery: A retrospective cohort study. BMC Oral Health 2022;22(1):8. doi. org/10.1186/s12903-022-02046-z.

43. Bennett GW, Kim SK. Comparison of the fit of surgical guides manufactured with low-cost 3D printers. Gen Dent 2022;70(1):18–21.

44. Rouze l’Alzit F, Cade R, Naveau A, et al. Accuracy of commercial 3D printers for the fabrication of surgical guides in dental implantology. J Dent 2021;117:103909. doi. org/10.1016/j.jdent.2021.103909.

45. D’Haese J, Ackhurst J, Wismeijer D, et al. Current state of the art of computer-guided implant surgery. Periodontol 2000 2017;73(1):121–133. doi: 10.1111/prd.12175.

46. Dental Tribune. X-Nav receives FDA clearance for its navigational tool for implant surgery. 2020.

47. ClaroNav. Navident Receives FDA 510(k) Clearance. Toronto, Ontario, Canada; 2016.

48. Wu Y, Wang F, Fan S, et al. Robotics in Dental Implantology. Oral Maxillofac Surg Clin North Am 2019;31(3):513–518. doi: 10.1016/j.coms.2019.03.013. Epub 2019 May 15.

49. Mandelaris GA, Stefanelli LV, DeGroot BS. Dynamic navigation for surgical implant placement: Overview of technology, key concepts and a case report. Compend Contin Educ Dent 2018;39(9):614–621; quiz 622.

50. Neocis Inc. Indications for Use. Miami. Accessed July 12, 2022.

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THE CORRESPONDING AUTHOR, Tobias Boehm, DDS, PhD, can be reached at tboehm@westernu.edu.