Clinical Applications of Digital Dental Technology

Contributors

Nadim Z. Baba, DMD, MSD

Professor, Department of Restorative Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA, USA

Francesca Bonino, DDS

Postgraduate resident, Department of Periodontology, Tufts University School of Dental Medicine, Boston, MA, USA

Jacinto A. Cano Peyro, DDS

Instructor, Department of Prosthodontics & Operative Dentistry, Tufts University School of Dental Medicine, Boston, MA, USA

Carl F. Driscoll, DMD

Professor and Director, Advanced Education in Prosthodontics, Department of Endodontics, Prosthodontics, and Operative Dentistry, School of Dentistry, Maryland, Baltimore, MD, USA

Dennis J. Fasbinder, DDS

Clinical Professor, Department of Cariology, Endodontics, and Restorative Services, University of Michigan School of Dentistry, Ann Arbor, MI, USA

Ashraf F. Fouad, BDS, DDS, MS

Professor and Chair, Department of Endodontics, Prothodontics and Operative Dentistry, School of Dentistry, University of Maryland, Baltimore, MD, USA

Charles J. Goodacre, DDS, MSD

Professor, Restorative Dentistry, Loma Linda University, School of Dentistry, Loma Linda, CA, USA

Gerald T. Grant DMD, MS

Captain, Dental Crops, United States Navy, Service Chief, 3D Medical Applications Center, Department of Radiology, Walter Reed National Military Medical Center, Director of Craniofacial Imaging Research, Naval Postgraduate Dental School, Bethesda, MD, USA

Gary D. Hack

Associate Professor and Director of Clinical Stimulation, Department of Endodontics, Prosthodontics, and Operative Dentistry, School of Dentistry, University of Maryland, Baltimore, MD, USA

Julie Holloway, DDS, MS

Professor and Head, Department of Prosthodontics, The University of Iowa College of Dentistry, Iowa City, IA, USA

Jason Jamali, DDS, MD

Clinical Assistant Professor, Department of Oral and Maxillofacial Surgery, University of Illinois, Chicago, IL, USA

Georgios Kanavakis, DDS, MS

Assistant Professor, Department of Orthodontics and Dentofacial Orthopedics, Tufts University, School of Dental Medicine, Boston, MA, USA

Mathew T. Kattadiyil, BDS, MDS, MS, FACP

Director, Advanced Specialty Education Program in Prosthodontics, Loma Linda University School of Dentistry, Loma Linda, CA, USA

Joanna Kempler, DDS, MS

Clinical Assistant Professor, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland, Baltimore, MD, USA

Antonia Kolokythas, DDS, MSc

Associate Professor, Program Director, Department of Oral and Maxillofacial Surgery, Multidisciplinary Head and Neck Cancer Clinic, University of Illinois at Chicago, Chicago, IL, USA

Radi Masri, DDS, MS, PhD

Associate Professor, Advanced Education in Prosthodontics, Department of Endodontics, Prosthodontics, and Operative Dentistry, School of Dentistry, Maryland, Baltimore, MD, USA

Michael Miloro, DMD, MD, FACS

Professor and Head, Department of Oral and Maxillofacial Surgery, University of Illinois at Chicago, Chicago, IL, USA

Alexandra Patzelt, DMD, Dr med dent

Visiting Scholar, Department of Periodontics, School of Dentistry, University of Maryland, Baltimore, MD, USA

Sebastian B. M. Patzelt, DMD, Dr med dent

Associate Professor, Department of Prosthetic Dentistry, Center for Dental Medicine, Medical Center – University of Freiburg, Freiburg i. Br., Germany

Jeffery B. Price, DDS, MS

Associate Professor, Director of Oral & Maxillofacial Radiology, Department of Oncology & Diagnostic Sciences, University of Maryland School of Dentistry, Baltimore, MD, USA

Carroll Ann Trotman, BDS, MS, MA

Professor and Chair, Department of Orthodontics, Tufts University School of Dental Medicine, Boston, MA, USA

Hans-Peter Weber, DMD, Dr med dent

Professor and Chair, Department of Prosthodontics and Operative Dentistry, Tufts University School of Dental Medicine, Boston, MA, USA

Foreword

Advances in technology have resulted in the development of diagnostic tools that allow clinicians to gain a better appreciation of patient anatomy that then leads to potential improvements in treatment options. Biomechanical engineering coupled with advanced computer science has provided dentistry with the ability to incorporate three-dimensional imaging into treatment planning and surgical and prosthodontic treatment. Optical scanning of tooth preparations and dental implant positions demonstrates accuracy that is similar to or possibly an improvement upon that seen with traditional methods used to make impressions and create casts.

For example, with this technology, orthodontic treatment can be reevaluated to assess outcomes. Today, orthodontic treatment can be planned and executed differently. With CT scanning on the orthodontic patient, dentists can better understand the boney limitation of a proposed treatment and timing of the treatment and dental implants can be used to create anchorage to move the teeth more easily. Every aspect of dentistry has been affected by digital technology, and in most instances, this has resulted in improvements of clinical treatment.

Restorative Dentistry and Prosthodontics are likely to experience the most dramatic changes relative to the incorporation of digital technology. Three-dimensional imaging provides the clinician with an ability to analyze bone quantity and quality that should lead to more effective development of surgical guides. Likewise, hard and soft tissue grafting may be anticipated in advance, which will allow improved site development for esthetics and function. Such planning allows more affective provisionalization of the teeth and implants. By digitally understanding the design and tooth position, a provisional prosthesis can be fabricated using a monolithic premade block of acrylic, composite, or hybrid resin, thereby improving the ultimate strength of these prostheses. Dental material science has responded by producing materials that are more esthetic and can best provide a better potential for long-term survival and stability. Dental ceramics now can be milled on machines that can accept ever-improving algorithms to provide the most accurate prosthesis. Today, materials such as lithium disilicate, zirconia, and titanium are easily milled in machines that are self-calibrating and can eliminate the cuttings, so that accuracy is insured. In-office or in-laboratory CAD/CAM equipment is constantly improving, and it is clear that in years to come surgical guides and most types of ceramic restorations will able to be produced accurately and predictably in the office environment. This will change some of the duties of the dental technologist but in no way will compromise the necessity of having these trained and very talented professionals more involved in designing, individualizing color and characterization, correcting marginal discrepancies, and refining the prosthetic occlusions that are required. The dental technologist represents the most important function in delivering a restoration, that of quality control.

The future is exceedingly bright for all involved in the provision of dental care; moreover, the incorporation of digital dental procedures promises to improve care for the most important person in the treatment team, the patient.

The authors should be commended for bringing such valuable information and insight to the profession. At this point, information is what everyone most desire and one can be very proud of all the efforts forward-thinking professionals, engineers, and material scientists are bringing to the table. An honest appraisal of where we are today and what the potential future can be will drive the industry to create better restorative materials and engineered equipment and algorithms to dentistry.

Kenneth Malament

Preface

The evolution of the art and science of dentistry has always been gradual and steady, driven primarily by innovations and new treatment protocols that challenged the conventional wisdom such as the invention of the turbine handpiece and the introduction of dental endosseous implants.

While these innovations were few and far between, the recent explosion in digital technology, software, scanning, and manufacturing capabilities caused an unparalleled revolution leading to a major paradigm shift in all aspects of dentistry. Not only is digital radiography routine practice in dental clinics these days, but virtual planning and computer-aided design and manufacturing are also becoming mainstream. Digital impressions, digitally fabricated dentures, and the virtual patient are no longer science fiction, but are, indeed, a reality.

A new discipline, digital dentistry, has emerged, and the dental field is scrambling to fully integrate it into clinical practice and educational curriculums and as such, a comprehensive textbook that details the digital technology available and describes its indications, contraindications, advantages, disadvantages, limitations, and applications in the various dental fields is sorely needed.

There are a limited number of books and book chapters that address digital radiography, digital surgical treatment planning, and digital photography, but none address digital dentistry comprehensively. Although these topics will be addressed in this book, the scope is entirely different. The main focus is the practical application of digital technology in all aspects of dentistry. Available technologies will be discussed and critically evaluated to detail how they are incorporated in daily practice across all specialties. Realizing that technology changes rapidly, developing technologies and those expected to be on the market in the future will also be discussed.

Thus, this book is intended for a broad audience that includes dental students, general practitioners, and specialists of all the dental disciplines including prosthodontists, endodontists, orthodontists, oral and maxillofacial surgeons, periodontists, and oral and maxillofacial radiologists. It is also useful for laboratory technicians, dental assistants and dental hygienists, and anyone interested in recent digital advances in the dental field. We hope that the reader will gain a comprehensive understanding of digital applications in dentistry.

Chapter 1

Digital Imaging

Jeffery B. Price and Marcel E. Noujeim

Introduction

Imaging, in one form or another, has been available to dentistry since the first intraoral radiographic images were exposed by the German dentist, Otto Walkhoff (Langland et al., 1984), in early 1896, just 14 days after W.C. Roentgen publicly announced his discovery of X-rays (McCoy, 1919; Bushong, 2008). Many landmark improvements have been made over the more than 115-year history of oral radiography.

The first receptors were glass, however, film set the standard for the greater part of the twentieth century until the 1990s, when the development of digital radiography for dental use was commercialized by the Trophy company who released the RVGui system (Mouyen et al., 1989). Other companies such as Kodak, Gendex, Schick, Planmeca, Sirona, and Dexis were also early pioneers of digital radiography.

The adoption of digital radiography by the dental profession has been slow but steady and seems to have been governed, at least partly, by the diffusion of innovation theory espoused by Dr. Everett Rogers (Rogers, 2003). His work describes how various technological improvements have been adopted by the endusers of technology throughout the second half of the twentieth century and the early twenty-first century. Two of the most important tenets of adoption of technology are the concepts of threshold and critical mass.

Threshold is a trait of a group and refers to the number of individuals in a group who must be using a technology or engaging in an activity before an interested individual will adopt the technology or engage in the activity. Critical mass is another characteristic of a group and occurs at the point in time when enough individuals in the group have adopted an innovation to allow for self-sustaining future growth of adoption of the innovation. As more innovators adopt a technology such as digital radiography, the perceived benefit of the technology becomes greater and greater to ever-increasing numbers of other future adopters until eventually the technology becomes commonplace.

Digital radiography is the most common advanced dental technology that patients experience during diagnostic visits. According to one leading manufacturer in dental radiography, digital radiography is used by 60% of the dentists in the United States (Tokhi, J., 2013, personal communication). If you are still using film, the question should not be Should I switch to a digital radiography system?, but instead Which digital system will most easily integrate into my office?

This leads to another question, what advantages does digital radiography offer the dental profession as compared to simply continuing with the use of conventional film? What are the reasons that increasing numbers of dentists are choosing digital radiographic systems over conventional film systems? Let us look at them.

Digital versus conventional film radiography

The most common speed class, or sensitivity, of intraoral film has been, and continues to be, D-speed film; the prime example of this film in the US market is Kodak's Ultra-Speed (NCRP, 2012). The amount of radiation dose required to generate a diagnostic image using this film is approximately twice the amount required for Kodak's Insight, an F-speed film. In other words, F-speed film is twice as fast as D-speed film. According to Moyal, who used a randomly selected survey of 340 dental facilities from 40 states found in the 1999 NEXT data, the skin entrance dose of a typical D-speed posterior bitewing is approximately 1.7 mGy (Moyal, 2007). Furthermore, according to the National Council on Radiation Protection and Measurements (NCRP) Report #172, the median skin entrance dose for a D-speed film is approximately 2.2 mGy while the typical E-F-speed film dose is approximately 1.3 mGy and the median skin entrance dose from digital systems is approximately 0.8 mGy (NCRP, 2012). According to NCRP Report #145 and others, it appears that dentists who are using F-speed film tend to overexpose the film and then under develop it; this explains why the radiation dose savings with F-speed film is not as great as it could be because F-speed film is twice as fast as D-speed film (NCRP, 2004; NCRP, 2012). If F-speed film were used per the manufacturers' instructions, the exposure time and/or milliamperage (total mAs) would be half that of D-speed film and the radiation dose would then be half.

Why has there been so much resistance for dentists to move away from D-speed film and embrace digital radiography? First of all, operating a dental office is much like running a fine-tuned production or manufacturing facility; dentists spend years perfecting all the systems needed in a dental office, including the radiography system. Changing the type of imaging system risks upsetting the dentist's capability to generate comprehensive diagnoses; therefore, in order to persuade individual dentists to change, there has to be compelling reasons, and, until recently, most of the dentists in the United States have not been persuaded to make the change to digital radiography. It has taken many years to reach the threshold and the critical mass for the dental profession to make the switch to digital radiography. Moreover, in all likelihood, there are dentists today who will retire from active practice before they switch from film to digital.

There are many reasons to adopt digital radiography: decreased environmental burdens by eliminating developer and fixer chemicals along with silver and iodide bromide chemicals; improved accuracy in image processing; decreased time required to capture and view images, which increases the efficiency of patient treatment; reduced radiation dose to the patient; improved ability to involve the patient in the diagnosis and treatment planning process with co-diagnosis and patient education; and viewing software to dynamically enhance the image (Wenzel, 2006; Wenzel and Møystad, 2010; Farman et al., 2008). However, if dentists are to enjoy these benefits, the radiographic diagnoses for digital systems must be at least as reliably accurate as those obtained with film (Wenzel, 2006).

Two primary cofactors seem to be more important than others in driving more dentists away from D-speed and toward digital radiography – the increased use of computers in the dental office and the reduced radiation doses seen in digital radiography. We will explore these factors further in the next section.

Increased use of computers in the dental office

This book's focus is digital dentistry and later sections will deal with how computers interface with every facet of dentistry. The earliest uses of the computer in dentistry were in the business office and accounting. Over the ensuing years, computer use spread to full-service practice management systems with digital electronic patient charts including digital image management systems. The use of computers in the business operations side of the dental practice allowed dentists to gain experience and confidence in how computers could increase efficiency and reliability in the financial side of their practices. The next step was to allow computers into the clinical arena and use them in patient care. As a component of creating the virtual dental patient, initially, the two most prominent roles were electronic patient records and digital radiography. In the following sections, we will explore the attributes of digital radiography including decreased radiation doses as compared to film; improved operator workflow and efficiency; fewer errors with fewer retakes; wider dynamic range; increased opportunity for co-diagnosis and patient education; improved image storage and retrievability; and communication with other providers (Farman et al., 2008; Wenzel and Møystad, 2010).

Review of basic terminology

Throughout this section, we will be using several terms that may be new to you, especially if you have been using conventional film; therefore, we will include the following discussion of some basic oral radiology terms, both conventional and digital. Conventional intraoral film technology, such as periapical and bitewing imaging, uses a direct exposure technique whereby the X-ray photons directly stimulate the silver bromide crystals to create the latent image. Today's direct digital X-ray sensor refers most commonly to a complementary metal oxide semiconductor (CMOS) sensor that is directly connected to the computer via a USB port. At the time of the exposure, X-ray photons are detected by cesium iodide or perhaps gadolinium oxide scintillators within the sensor, which then emit light photons; these light photons are then detected within the sensor pixel by pixel, which allows for almost instantaneous image formation on the computer display. Most clinicians view this instantaneous image formation as the most advantageous characteristic of direct digital imaging.

The other choice for digital radiography today is an indirect digital technique known as photostimulable phosphor or PSP plates; these plates resemble conventional film in appearance and clinical handling. During exposure, the latent image is captured within energetic phosphor electrons; during processing, the energetic phosphors are stimulated by a red laser light beam; the latent energy stored in the phosphor electrons is released as a green light, which is captured, processed, and finally digitally manipulated by the computer's graphic card into images relayed to the computer's display. The indirect term refers to the extra processing step of the plates as compared to the direct method when using the CMOS sensor. The most attractive aspect of PSP may be that the clinical handling of the phosphor plates is exactly like handling film; so, most offices find that the transition to PSP to be very manageable and user-friendly.

Panoramic imaging commonly uses direct digital techniques as well. The panoramic X-ray beam is collimated to a slit; therefore, the direct digital sensor is several pixels wide and continually captures the signal of the remnant X-ray beam as the panoramic X-ray source/sensor assembly continually moves around the patient's head; the path of the source/sensor assembly is the same whether the receptor is an indirect film, PSP, or direct digital system. Clinicians who are using intraoral direct digital receptors generally opt for a direct digital panoramic system to avoid the need to purchase a PSP processor for their panoramic system.

Orthodontists require a cephalometric system and when moving from film to digital, again have two choices: direct digital and indirect digital. The larger flat panel digital receptor systems provide the instantaneous image but are slightly more costly than the indirect PSP systems; however, the direct digital systems obviate the need to purchase and maintain PSP processors. The higher the volume of patients in the office, the quicker is the financial payback for the direct digital X-ray machine.

Image quality comparison between direct and indirect digital radiography

Some dentists will make the decision of which system to purchase based solely on the speed of the system, with the direct digital system being the fastest. There are other factors as well: dentists often ask about image quality. Perhaps the better question to ask may be, Is there a significant difference between the diagnostic capability of direct and indirect digital radiography systems? One of the primary diagnostic tasks facing dentists on a daily basis is caries diagnosis, and there are several studies that have evaluated the efficacy of the two systems at this common task. The answer is that there is no difference between the two systems in diagnostic efficacy – either direct digital or indirect digital with PSP plates will diagnose caries equally well, in today's modern systems (Wenzel et al., 2007; Berkhout et al., 2007; Li et al., 2007).

One important consideration to consider when comparing systems is to make sure that the images have the same bit depth. Bit depth refers to the numbers of shades of gray used to generate the image and are expressed exponentially in Table 1.1.

Table 1.1 Bit depth table that gives the relation of the exponential increase in the number of shades of gray available in images as the bit depth increases

The early digital systems had a bit depth of 8 with 256 shades of gray, which may seem fine because the human eye can only detect approximately 20 to 30 shades of gray at any one time in any one image; however, most digital systems today generate images at 12 or even 16 bit depth, that is, images that have 4,096 to 65,536 shades of gray (Russ, 2007). Proper image processing is a skill that must be learned in order to fully utilize all of the information contained in today's digital images. Conventional film systems do not have discrete shades of gray; rather, film systems are analog and have an infinite number of possible shades of gray depending only on the numbers of silver atoms activated in each cluster of silver atoms in the latent image within the silver halide lattice of the film emulsion. Therefore, when comparing systems, ensure that the bit depth of the systems is comparable; and, remember that over time, the higher bit depth systems will require larger computer storage capacities due to the larger file sizes associated with the increased amount of digital information requirements of the larger bit depth images. It is expected that in the future, most systems will use images of a minimum of 12 bit depth quality and many are already using images of 16 bit depth