Implants and Digitization

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© Springer Nature Switzerland AG 2021

P. Jain, M. Gupta (eds.)Digitization in Dentistrydoi.org/10.1007/978-3-030-65169-5_12

12. Dental Implants and Digitization

Nitish Surathu1, Ali Tunkiwala2 and Udatta Kher2  
(1)

Private practice, Gisborne, New Zealand
(2)

Private Practice, Mumbai, India
 
Keywords

Dental implantsNavigationCAD/CAM

12.1 Introduction

The last couple of decades have seen a tremendous increase in the use of computer-driven technology to automate several processes in the dental industry. The use of computer-aided design (CAD) and computer-aided manufacturing (CAM) have transformed the process of design, manufacture, and delivery of many dental services [1]. Restorative dentistry has probably been the largest gainer of this transformation. Dental implantology however comes a close second and digital technology has brought dental radiology, implant surgery, and implant prosthodontics together in a manner that few could have envisioned possible.

12.2 History and Development

In the late 1980s, the osseointegrated root-form implant began to see extensive clinical use as a modality to replace teeth. Professor Branemark had completed several years of clinical research that saw the modality become popular clinically [2]. The root-form implant held several geometric advantages over other forms of previously practiced endosseous implants such as blade implants and ramus frames. A cylindrical shape with a screw thread of definitive diameter and length quickly became the most popular. The geometry of this type of implant lent itself very easily to large-scale commercial manufacturing.

Several companies began to manufacture implants using computer numeric controlled (CNC) lathes which are still the mainstay of the industry. These CNC lathes themselves became extremely accurate and in time were able to manufacture extremely high accuracy tolerances. This allowed for excellent componentry fit and restorative predictability (R). Once endosseous root-form implants had established themselves as an accepted modality of treatment, the industry began to face challenges with clinical demands for restorative customization. A growing esthetic demand for implant restorations to be as natural as possible drove this increased demand for customization as well. The industry stepped up to the challenge and invested in CNC manufacturing of customized restorative componentry. The early 2000s saw the creation of large facilities dedicated to CAD/CAM design of custom abutments, restorations, and other restorative componentry such as bars [3]. These facilities provided multilocation high-end computer-aided manufacturing and served to eliminate expensive investment in the equipment required.

As implant restorative dentistry itself became more customized, it became obvious to the industry that control of the surgical process would be the next challenge. Specialists with surgical skills and general dentists with sufficient surgical aptitude had already taken to offering dental implant services to their patients. There still remained a large cohort of clinicians who could consider implant services, if surgical predictability became a reality. A demand for greater surgical predictability also came to be a result of implants being used for more complex rehabilitation. Full arch implant rehabilitations were particularly surgically challenging and demanded better anatomical understanding. Implants also began to be used in bone deficient situations with increased grafting [4, 5]. The development of techniques that incorporated angled implants also saw a greater demand for surgical skill in terms of accommodation of the patient’s anatomy [6, 7] (Fig. 12.1).

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Fig. 12.1

Customized angled overdenture design

The development of cone beam computerized tomography at around the same time also made three-dimensional radiographic visualization of anatomy a reality [8, 9]. It remained up to the industry to marry these digital technologies together and develop a protocol for more accurate surgery.

Much research in the late 90s and early 2000s eventually saw the development of guided implant surgery. The development of surgical guides and instrumentation that allowed accurate preparation of bone for a dental implant became very popular over time [10, 11]. Several dentists with a moderate surgical skill set as well as clinicians demanding greater planning accuracy for complex cases, became supporters of guided implant surgery. The surgical guides themselves were made at the time in centralized CAM facilities that employed rapid prototyping technology [12, 13]. The gradual erosion of the cost of computer-aided manufacturing, both in milling and rapid prototyping, eventually made the consideration of chair-side use of these technologies a reality.

The industry as it stands today has completely decentralized these technologies and moved them into the dentist’s office [14, 15]. The evolution of better milling technology has also seen chair-side milling of custom titanium and zirconia componentry become a possibility. The development of low-cost 3D printing has also meant that the manufacture of surgical guides with complex geometries can also become chair-side [1618] (Fig. 12.2).

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Fig. 12.2

A safe guide with lateral access from Simplant

Software business models that had once focused on centralized manufacturing for a fee, have now largely become low cost or even free, sometimes allowing a cost to be incurred only when needed. We are therefore at a very exciting juncture with regard to the digitization of implant dentistry and the future is bright.

This chapter seeks to chronologically elaborate on several aspects of this digitization process that have come to be a reality today. The idea is to educate the reader about multiple digital technologies that are currently available with regard to multiple aspects of the delivery of clinical implant dentistry.

12.3 Implant Manufacturing

The earliest root-form implants were hand manufactured from titanium rods. Over the years, the process became mechanized, and large industrial precision lathes began to be used for the manufacture of root-form implants. The advent of computer-aided design and manufacturing saw this process become more and more digitized [1921]. Computer numeric controlled lathes today are capable of manufacturing dental implants and componentry with as little as a 2-micron tolerance. Advances in computer numeric control lathe technology have also allowed the manufacture of more and more specialized restorative componentry that has needed multiaxis machining. The industry is today capable of producing high precision componentry that allows the restorability of implants in multiple difficult situations. Examples include the manufacture of zygomatic [22, 23] and nasal floor implant as well as angulated screw channel [24, 25] restorative components and the use of materials such as zirconia titanium alloys in the manufacture of dental implants. Advances have also meant an advancement of production efficiencies and quantities and implant companies are today able to service a multibillion-dollar worldwide industry that sees hundreds of thousands of implants placed annually. The future is likely to see the evolution of newer implant material types and the customization of dental implants for unique situations (Fig. 12.3).

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Fig. 12.3

Azento concept all-inclusive implant solution

12.4 Restorative Componentry

The late eighties saw the development of restorative CAD and CAM technologies in Europe. Companies began to be able to manufacture custom restorations in ceramics and custom componentry in titanium. Large industry players moved to acquire this technology and the nineties saw the introduction of either centralized manufacturing facilities for restorations or their componentry or the advent of early chair-side milling solutions [14, 2628]. Computer-aided designing came to start to replace what was traditionally handcrafted by dental technicians. The quality of custom implant componentry actually began to enhance restorative outcomes. Dental technicians themselves moved to automate their own design manufacturing processes and sought to outsource much of what they produced to large centralized manufacturing facilities that invested in multimillion-dollar multiaxis milling machines. Manufacturing capabilities of these machines began to include full arch restorations in zirconia and titanium as well, including full-arch bridges, titanium substructures, and titanium bars.

The quality and passivity of fit even in cross-arch situations were often exemplary and computer-aided manufacturing helped address many of the weaknesses of conventional restorative manufacturing. Many cross-arch cast restorative solutions were heavy, expensive, and sometimes inaccurate [29, 30]. Milled single- and multiple-unit restorative componentry slowly began to become the mainstay of the implant industry [31, 32]. The real advances in the manufacture of restorative componentry however began to come when manufacturing began to become decentralized. Computer-aided manufacturing technologies gradually became more portable and the industry began to develop desktop milling solutions that returned control to the dental technician. Dental technicians themselves needed to adapt to technological change and move to learn and use digital software to replace conventional manufacturing. Multiaxis manufacturing lathes are now easily available as desktop solutions and mill ceramics, zirconia, titanium, cobalt chrome, wax, techno polymers, acrylics, and composite [33, 34]. The wide range of capability of these machines has also meant that dental laboratories have become extensively digitized.

Chair-side milling technology has also seen significant change over the last decade. Dentists are able to provide chair-side milling solutions in ceramics, composite, and zirconia that often see them able to deliver restorations in one appointment. Newer milling machines are also capable of milling titanium abutments and non-precious metal restorations, giving today’s digital dentist many more additions to his clinical repertoire [3537]. Chair-side design technologies have also put the clinician more in power of single-unit restorations, in particular, giving a dentist the ability to design crowns, veneers, implant abutments, implant restorations, and inlays and onlays. The sheer range of materials that have become available for chair-side milling is also impressive with materials such as composites, feldspar ceramics, leucite reinforced ceramics, ceramic-composite hybrids, zirconia, acrylics, non-precious alloy and lithium silicates/disilicates/zirconia reinforced silicates, all being available in the form of blocks that are accepted by chair-side mills. Advances have also included the ability of these machines to dry mill and wet mill, thus reducing processing times for post milling sintering or crystallization [38, 39].

Technologies in furnace development have also kept pace and provided dentists with chair-side solutions that are capable of an extremely rapid rise in sintering/crystallization temperatures as well as rapid cooling. The fastest mills are capable of milling some materials in less than 5 min with sintering/crystallization taking only another 10 min [40, 41]. These technologies have therefore resulted in the creation of chair-side restorations while the patient waits. The expansion of the envelope of single appointment dentistry is a reality of dental practice today and dentists have no alternative but to embrace computer-aided design and manufacturing to be able to offer it.

12.5 Digital Impression in Implant Dentistry

Chair-side intraoral scanning has also seen significant evolution in the last decade. The use of contrast sprays and 2D photography that stitched images together is something of the past and the scanners of today are capable of full color realistic 3d imagery. Exceptional speeds of data acquisition have also resulted in greater acceptance for intraoral scanners [4143]. The trueness of intraoral scans has also been scientifically assessed with a variety of scanners. It is interesting to see that intraoral scanners are today capable of cross arch accuracy that is comparable to or better than dental impressions with the best impression materials (Fig. 12.4).

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Fig. 12.4

STL wireframes that form the basis of most 3D images

It is realistically possible today to consider the elimination of conventional impressions, at least in most dentate cases if not all cases. Intraoral scanners of today are also able to accurately image to a depth of 20 millimeters, allowing a large envelope for the size of restorations possible and their sub-gingival extent. Some advanced intraoral scanners are also capable of accounting for fluids such as blood and saliva and compensating for refractive error that may otherwise result.

More information on the types of scanners and their descriptions/uses is given in Chap. 11.

Dynamic intraoral scanning has also become a reality today and it is actually possible to generate genuine articulation between intraoral scans of opposing arches as long as static and excursive bite records are obtained. Software advances have also resulted in an increased ability to integrate various digital data sets. Intraoral scans are therefore integratable not just with cone beam computed tomography volumes but also facial scans and impression generated models or wax-ups [44, 45] (Fig. 12.5).

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Fig. 12.5

Integrated facial and intraoral scans

Integration of this nature allows substantial cross over between the digital and analog worlds. Clinicians and technicians are therefore able to choose workflows that they prefer and still manage continuity of flow from a digital workspace to an analog workspace and vice versa. Data sizes of intraoral scans have also become far more efficient with the evolution of newer file formats that allow greater mesh compression. This directly translates into ease of digital transfer and allows clinicians and technicians and other providers in various parts of the world to come together in one workspace.

The laboratory equivalent of intraoral scans is the model scanner that uses largely similar scanning principles. Model scanners typically scan impressions or poured-up dental models. In general, the direct scanning of impressions has always presented difficult challenges, with undercuts in an impression allowing limited access to a scanner. This is still best addressed by pouring up an analog model that can be scanned. It however continues to compel an analog step in a workflow that can otherwise be completely digital. The best digital solution offered for this problem continues to be the CBCT scanning of impressions and their inversion using 3D rendering software [4648]. To some degree, the access of intraoral scanner heads does limit the amount of data that can be acquired by an intraoral scanner. It is expected that the size of intraoral scanners and their field of view will continue to see the improvement that will overcome these obstacles. The power consumption of intraoral scanners has also meant the development of models that can be battery supported, thus allowing greater portability.

This is a tremendous advantage in multioperatory dental offices and can serve to reduce a practice’s investment. The weight of intraoral scanners has also come down with time, despite the incorporation of heating of fans to reduce fogging. If anything, the pace of development continues to pose a challenge for rapid technological redundancy, and this can be an issue if the investment is not a well-thought-out decision. New generation intraoral scanners are also attempting to integrate other emerging technologies such as subtractive superimpositional techniques that allow for assessment of changes in a dentition such as wear, migration, or recession. Some scanners have also incorporated caries detection and transillumination modalities that allow for illuminative structural assessment of teeth.

12.5.1 Scan Bodies

In effect, the dramatic advances in intraoral scanning have meant that all impression procedures in implant dentistry can be truly and completely digitized. This has led to the development of multiple scan bodies that are really replacements for conventional impression copings in implant dentistry [49]. Scan bodies have tended to be unique to commercially developed digital workflows in order to ensure sanctity in the workflow with minimal room for error [50, 51]. Some have however become more popular than others, driven largely by their acceptance by commercial CAD design software packages. Many scan bodies offer a titanium base, a polymer replaceable post, and digital libraries that can be imported into popular CAD software. These digital libraries allow the creation of digital or physically printed 3D models that become working models for dental laboratories. The accuracy of scan bodies has meant that their use in cross arch situations is also possible. Indeed, scan bodies have also been employed in full arch situations for the development of milled multi-unit prosthesis in titanium, zirconia, and techno polymers. Some companies have also offered integration between scan bodies and custom abutment manufacturing (Figs. 12.6 and 12.7).

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Fig. 12.6

Acuris conometric concept

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Fig. 12.7

Custom abutments from Atlantis

These custom abutments are often fabricated with a high degree of accuracy on either 5 axis lathes or computer numeric controlled lathes that are capable of generating custom abutments with a quality that is similar to prefabricated stock implant componentry. Some of these manufacturers even allow dentists to mill their restorations from core restoration files supplied by them(R). This ensures that costs are further curbed, and dentists are able to have well designed implant restorations that offer a quality fit on custom implant abutments.

12.5.2 Photogrammetry

The other dramatic improvement in implant impressions has come about with the use of photogrammetry (Fig. 12.8). This technique allows the registration of the exact three-dimensional location of the implants using 3D coordinate measurements to record geometric properties. Photogrammetry [52, 53] has been shown to be highly accurate in implant dentistry and ensures the minimization of inaccuracies in cross arch digital impressions. At least two systems are now commercially available and offer a package that includes specially designed implant mounts with geometric imagery and a photogrammetry camera that accurately records three-dimensional orientation. It is anticipated that photogrammetry may well become the technique of choice for accurate impressions in restorative full-arch dentistry.

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Fig. 12.8

Photogrammetry scan markers in an All on 4 (Courtesy of Dr Han Choi, Auckland)

12.6 Guided Implant Surgery

The longest-standing digitization protocol in implant dentistry has for long been the field of computer-guided implant surgery [54] (Fig. 12.9). The technique fundamentally integrates digital restorative data with radiographic data in order to provide a clinician with a restorative guideline. This allows the use of this guideline over a radiographic representation of bone at a proposed site, to accurately plan an implant’s position. The earliest versions of this technology either utilized diagnostic wax-ups that were scanned using model scanners or acrylic partial/complete dentures with radiographic gutta-percha markers. In its earliest days, the technique also used conventional medical-grade axial tomography that resulted in significant radiation exposure. The development of cone beam computed tomography brought about a significant change with regard to reduced radiation exposure levels. It gradually becomes cost realistic for dental practices as well to incorporate cone beam computed tomography into their practices. This one development alone has resulted in an explosion of the use of guided implant surgical techniques.

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Fig. 12.9

Planning image with color intraoral scan import

The earliest software packages were developed in Belgium and were tested extensively in multi-center clinical trials. At the time, most guided surgical stents were developed using stereolithographic techniques for rapid prototyping in centralized facilities. The cost of these stents was prohibitive, but they added significantly to the accuracy of implant placement. Companies also moved to develop surgical instrumentation that was specific to guided surgery and surgical protocols that incorporated these stents quickly became popular with strong marketing.

The development of intraoral scanning and new software for cone beam computed tomography saw integration taken to a whole new level. Dentists were able to plan implant restorations chair-side on digital models, although they were limited to single restorations and short edentulous spans. These planned implant restorations were easily incorporated into guided surgery software resulting in very accurate implant planning. Recent Software packages include libraries for multiple implant systems, thus broadening the scope for use of guided surgery. Software packages have now become increasingly intuitive as well, allowing users to slice data in a variety of custom planes that went beyond conventional multi-planar radiology [5557]. This allowed users to place implants at any angle of their choice while still being able to assess distances, angles, and parallelism between multiple implants. Clinicians were also offered the ability to clearly delineate anatomical landmarks such as nerves in order to allow for accurate planning of implants in proximity to them. The ability to detect some of these landmarks has become increasingly more accurate with time as well, given high-resolution voxel sizes in current cone beam computed tomography machines. Some software today also allow volumetric planning of grafts in deficient sites [5860]. It has also become possible to generate accurate three-dimensional models from radiographic data and integrate this with data from intraoral scans, facial scans, and soft tissue scans. The generation of new file formats is also opening up possibilities for incorporation of full color in these data sets, adding a whole new dimension to aesthetically driven digital treatment planning that involves implants.

Significant improvement in guided surgery tooling has also meant that some of the initial difficulties with guide implant surgery are better addressed. One of the early limitations often used to be the size of drills and consequent limitations with regard to mouth opening in certain patients. Lateral access sleeves have allowed for easier access to guided surgery drills into a surgical guide, especially in posterior sites (Fig. 12.10). Many manufacturers have also moved to eliminate “Spoons” or “Keys” and attempted to incorporate a metal sleeve in the guide (Fig. 12.11). This approach has sometimes resulted in some loss of axial control but newer instrumentation incorporating sleeves directly on drills has addressed this (Fig. 12.12). Most instrumentation will likely become keyless in the future resulting in greater ease of use of surgical guides.

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