9.1 Introduction

Technological advancements and engineering breakthroughs have transformed the protocols of medical sciences. Digital technologies, artificial intelligence, and tele‐medicine have become inseparable parts of various medical fields (Seyhan and Carini 2019). Dentistry is not an exception, and increased computerization can be seen in clinical dentistry and dental research (Chen et al. 2020). Perhaps one of the pioneer dental fields to have adopted widespread digital workflows is implant dentistry. In fact, computer‐aided implant surgery (CAIS) is becoming the standard in both academic and private dental environments.

Cornerstone for CAIS was the development of cone beam computed tomography (CBCT), which allowed three‐dimensional (3D) and accurate visualization of bony structures at reduced radiation dosage (Guerrero et al. 2006). The total radiation of CBCT devices is approximately 20% less than that of a helical computed tomography (CT) and corresponds to the exposure of a full‐mouth periapical series (Mah et al. 2003).

At the same time, the leaders in implant dentistry pointed out the importance of converting information from planned slices to the tangible structures of the patient. The article was pioneering the discussion of 3D implant planning and ways to transfer the planned data to the surgical area to achieve anatomically safe implant placement (Verstreken et al. 1996). As implant dentistry evolved, it became clearer that prosthetically driven implant placement is equally important for esthetic results and long‐term success of implant‐retained restorations (Cooper 2008). With that in mind, earlier protocols included using radiopaque guides, which provided information regarding the future restoration (e.g. incisal edge position, cervical margin) in relation to the existing alveolar bone. These imaging guides were then converted into surgical templates to direct implant positioning (conventional guides).

Computer‐aided implant surgery has evolved and become more popular since then and entails proven advantages, such as reduced time for surgery, improved postoperative healing, anatomically safe and prosthetically driven implant placement, and reduced number of appointments. To a certain extent, it could even compensate for limited surgical experience (Vercruyssen et al. 2015).

Technological advancements and their integration in implant dentistry allowed the development of various CAIS protocols. Based on the type of workflow or technology that is chosen, CAIS can be categorized into two major types: computer‐guided (static) surgery and computer‐navigated (dynamic) surgery (Hammerle et al. 2009).

This chapter will review current technologies and protocols for CAIS. It will mostly focus on static CAIS, which has been adopted by clinicians globally. It describes workflows for various clinical scenarios, current protocols, and clinical applications as well as limitations and future directions. It also briefly summarizes workflows for dynamic computer‐aided and robot‐assisted implant surgeries for comparison purposes.

9.2 Prosthetically Driven 3D Implant Positioning

Success of dental implants have largely been described based on the evidence of osseointegration and implant survival (Albrektsson et al. 1986). However, implant success has been redefined, and some newer evaluation parameters have been introduced. Soft tissue health status, natural appearance, esthetics, and patient satisfaction were among the new criteria. Perhaps, one of the most important assessments is to evaluate the implant–prosthetic complex as a whole (Papaspyridakos et al. 2012).

The evaluation criteria of anterior implants have also been updated. The goal is to achieve implant‐retained restorations that are unnoticeable and provide esthetics equal to or better than the contralateral and adjacent teeth (Cooper 2008, Testori et al. 2018). This was called the “fine‐tuning phase” in implant dentistry (Buser et al. 2017).

Recent studies have pointed out the association between prosthetic features like restoration emergence contour and emergence angle with peri‐implant disease (Katafuchi et al. 2018, Yi et al. 2020). Specifically, overcontoured, convex prosthetic profiles had a significantly higher risk for developing peri‐implantitis. Not only peri‐implant disease, but also a higher incidence of caries was linked with implants that have more than 4 mm implant‐to‐tooth horizontal distance as measured at the alveolar crest. It is conceivable that large gingival embrasures and overcontoured restorations caused a 17% incidence of caries on adjacent teeth (Smith et al. 2020).

Thus, to avoid aforementioned comorbidities and achieve an implant‐retained prostheses with predictable long‐term success and favorable esthetic outcomes, optimal, prosthetically driven positioning of an implant in mesio‐distal, apico‐coronal, and bucco‐lingual dimensions is crucial. For missing single teeth, multiple references are present that can guide an experienced surgeon to ideal implant positioning. However, with multiple missing adjacent teeth, where the landmarks from adjacent and opposing teeth are absent, prosthetically correct free‐hand implant placement is rather challenging. In these instances, CAIS can provide both anatomically safe and prosthetically driven implant placement. Planning of a future restoration can be achieved with the help of radiopaque templates, temporary restorations, and/or computer‐aided design (CAD) software. This allows clinicians to plan the best possible implant position from a restorative point of view while taking into consideration the anatomy and the volume of the alveolar bone.

9.3 Computer‐Aided Implant Planning

As mentioned above, CBCT provides accurate 3D bone volume information at lower and safe radiation dose levels. Bone volumetric data is displayed in cross‐sectional images in relation to prospective implant position. Also, implant‐planning software can display 3D surface models. Due to different tissue characteristics, the volumetric data has various radiation attenuations. This can enable the selective display of anatomical structures (e.g. teeth, bone), referred to as segmentation. Nevertheless, digital‐imaging‐and‐communication‐in‐medicine (DICOM) files do not display sufficient detail of tooth surfaces for the digital design of prostheses and/or planning osteotomy guides. For this reason, optical scan Standard Tessellation Language (STL) files obtained through an intraoral or extraoral scan are incorporated with a DICOM file to merge the information of bone volume with tooth and soft tissue surface patterns. The process of superimposition of different imaging datasets is called registration. Multiple references can be used to achieve accurate registration/alignment. The most common one is probably the tooth surface. In the absence of teeth or the presence of highly radio‐opaque restorations (silver amalgam fillings, metal restorations, porcelain‐fused‐to‐metal restorations), custom reference markers (fiducial markers) are used, either attached to non‐mobile soft tissue surfaces or to radiographic templates (Kernen et al. 2020).

Most of the available software options have built‐in artificial intelligence algorithms to align corresponding anatomical surface references. Some of the software requires marking of certain corresponding areas to facilitate (semi‐automatic) registration. Accurate superimposition of various datasets is crucial for reliable implant planning. For this reason, clinicians often correct automated alignment and account for any possible inaccuracies (Margvelashvili‐Malament et al. 2019).

Following alignment of datasets, the next step is to acquire information about the future restoration (prosthetic plan). Most of the implant‐planning software options have built‐in CAD elements that allow virtual prosthetic set‐ups. Older software versions required a double‐scan technique, where two separate model scans were obtained: one with the missing teeth and the other with a wax‐up to incorporate the position and design of the future prosthesis. Alternative workflows with double scans were also proposed, where two intraoral scans are obtained: one with prepared teeth and one with the provisional restoration in place. A clinical example of this workflow is discussed below. This workflow is best suited for full‐mouth reconstructions, which entail provisionalization as a prior phase to implant surgery (Margvelashvili‐Malament et al. 2019).

Whether a double scan, double intraoral scan or the CAD features are used, the goal remains the same: prosthetically driven implant‐planning and placement. Clinicians should be able to visualize implant positions in the 3D bony environment in relation to a future restoration, adjacent teeth, emergence profile, incisal edge, cervical area, etc. (Kernen et al. 2020, Margvelashvili‐Malament et al. 2019).

9.4 Computer‐Aided Implant Surgery

Based on the type of workflow or technology chosen, CAIS can be categorized as two major types, which are defined as follows (Hammerle et al. 2009):

• Computer‐guided (static) surgery. The use of a static surgical template that reproduces the virtual implant position directly from CT data and does not allow for intra‐operative modification of the implant position.
• Computer‐navigated (dynamic) surgery. The use of a surgical navigation system that reproduces the virtual implant position directly from CT data and allows for intra‐operative changes in implant position.

The current protocol for computer‐aided static surgery incorporates a CBCT scan produced DICOM dataset with optical scan STL files allowing 3D planning in both virtual and a 3D bony environment. Based on the plan, a guide is then produced that copies the locked plan of the implant position to the surgical site (Jung et al. 2009).

Conversely, dynamic navigation does not require a surgical guide and allows visualization of osteotomy and implant placement in real time on a monitor (Block and Emery 2016, Edwards et al. 1999, Gargallo‐Albiol et al. 2019). Initially, the DICOM data is integrated into the navigation software to plan a 3D implant position. The surgeon then places implant and guides through visualizing on the screen (Block and Emery 2016, Edwards et al. 1999, Gargallo‐Albiol et al. 2019). Apart from the human‐controlled dynamic guidance, a relatively new system is the robot‐assisted implant surgery, which incorporates haptic guidance with dynamic computer‐assisted implant surgery. It physically guides and controls the surgeon’s hand to replicate planned implant angulation and positioning. Robot‐guided implant placement has the capability to track patient motion and adjust the parameters in real time (real‐time tracking). A surgeon can visually confirm the implant position on the monitor.

9.5 Static Computer‐Aided Implant Surgery and Guides

Once implant planning is completed, the osteotomy guide that will transfer the plan to the surgical site is designed. There are various types of static guides. Some allow a guided osteotomy followed by free‐hand implant placement, others offer guided osteotomy and guided implant placement, described as fully guided surgery (D’Haese et al. 2017). Fully guided surgery may use several guides in sequence of increasing drill diameters or a single guide with adjustable drill handles and appropriate sleeve diameters (Hammerle et al. 2009). The classification of static guides is summarized in Figure 9.1.

9.6 CAD/CAM Fabrication of Surgical Guides

In this technique, the planning data are transferred to the production center, which fabricates the surgical guides according to the given information, either via stereolithography or additive (3D printing) techniques.

9.6.2 Additive Manufacturing (3D Printing) of Guides

The principle of 3D printing is to slice a digital object in cross sections that are printed in layers (additive technique). Those layers are made of liquid, powder, or any sheet material and can be fused together to create objects with any shapes, including surgical guides. The accuracy requirements for anatomical models lie within a range of a tenth of a millimeter (Stopp and Luth 2007).

Treatment times and labor resource can be reduced when using 3D printing technology. The templates can be produced in a production center (centralized) or even in a local laboratory (decentralized). For the production in the local laboratory, a 3D printer capable of producing surgical guides is required. Of course, local fabrication requires special skills and experience in planning, designing, and manufacturing surgical guides. With proper knowledge, devices, and software, surgical guide manufacturing via 3D printing can be straightforward and fast.

9.6.5 Completely Edentulous Arches

Computer‐aided implant placement for completely edentulous patients relies on the same basic principles of completing a comprehensive examination and obtaining 3D data of bone, soft tissue surfaces, and future prosthesis.

Data acquisition can be accomplished through conventional or digital methods or by a combination of the two. The first step in the digital workflow is to obtain optical data of edentulous jaws. It can be done by making conventional impressions or fabricating casts, which are scanned with a desktop scanner, or fully digitally, using an intraoral scanner. The next step is to visualize the future restoration. This can be achieved by duplicating existing conventional dentures or a lab‐based tooth set‐up. The duplication of a pre‐existing denture often requires an intraoral reline of the duplicate to ensure adequate fit. In the event of a lab‐based tooth set‐up, intraoral confirmation and appropriate adjustments are required based on classic denture prosthodontic principles. When the CBCT is taken with the resin‐based denture, it is characterized by similar density and radiation attenuation of the soft tissues. Therefore, it is hard to differentiate either of the latter during segmentation (Vercruyssen et al. 2015). For this reason, an imaging appliance is fabricated based on the denture replica or tooth set‐up using a radio‐opaque material. The CBCT is taken with the imaging appliance. Ideal implant positioning, taking into consideration remaining alveolar bone volume and future prosthesis, is then planned to produce the surgical guide. A clinical case is presented in Figures 9.11–9.14 and Video 9.2.

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