Digital Workflow: Helping Clinicians Make Smart Decisions, Achieve Better Outcomes

Conventional intraoral 2-dimensional (2D) radiographic films (developed with chemicals) helped clinicians visualize anatomic structures on a light-box. These static black and white images enabled the diagnosis of dental caries, periodontal disease, bone loss, impacted teeth, and other pathologic entities. The digitization of intraoral radiography has made new tools available to the dental profession to aid in the diagnostic phase, shifting away from the analog light-box modality to improved interactive visualization with images on an LCD screen. Innovations have included the ability to zoom into areas of interest, modify gray-scale, use color, achieve accurate non-distorted measurements, and attain faster image acquisition times when using intraoral sensors. Whether analog or digital, 2D radiography is still considered standard of care for many routine dental procedures. However, as the author often cautions when lecturing, there is "danger when we use 2D concepts when clearly we live in a 3-dimensional (3D) world."

Interactive Treatment Planning

Two-dimensional imaging modalities can be important initially when planning for dental implant procedures or bone grafting, but they are severely limited in accuracy when determining bone density, thickness of cortical bony plates, path of the inferior alveolar nerve, visualization of intraosseous vessels, bony lesions, sinus pathology, or the distance between the lateral and medial walls of the maxillary sinus. In 2012, the official position paper of the American Academy of Oral and Maxillofacial Radiology stated that, "…the AAOMR recommends that cross-sectional imaging be used for the assessment of all dental implant sites and that [cone-beam computed tomography] CBCT is the imaging method of choice for gaining this information."¹

Subsequently, continued advances in computer hardware power, graphics accelerator cards, increased display resolution, and high-resolution monitors have provided the foundation for improvements in a variety of different interactive treatment planning software applications. Some examples of these include: Blue Sky Plan^® (Blue Sky Bio, blueskybio.com), coDiagnostix^® (Dental Wings, dentalwings.com), Implant Design Studio^® (3Shape, 3shape.com), Invivo (Anatomage, anatomage.com), NobelGuide (Nobel Biocare, nobelbiocare.com), SimPlant (Dentsply Sirona, dentsplysirona.com), and many more.

The expanded use of the Internet also has been instrumental, enabling the expedited conveyance of digital files back and forth between software applications, clinicians, and, most importantly, the dental laboratory, which is ultimately responsible for fabrication of the definitive prosthetic outcome. The previously mentioned interactive software applications have sufficiently evolved to bridge the gap between the CBCT-derived planning phase for dental implants and the CAD/CAM fabrication of both temporary and final restorations, as the ability to communicate with the dental laboratory technician has become a major catalyst for increased use of guided implant surgery procedures. To accommodate "restoratively driven" implant reconstruction² a plan that is based on the ultimate esthetic and functional position of the teeth is needed to provide the proper assessment of each potential implant receptor site before the scalpel ever touches the patient. The use of CBCT and interactive treatment planning software can now be supplemented with additional digital data created from the initial clinical presentation that is acquired by any of three accepted methods: conventional impressions, stone casts that are digitized using a desktop scanner; intraoral scanning; or scanning impressions or stone casts using the CBCT device itself. Regardless of which method is used, the purpose is to merge the acquired digital dataset with the CBCT dataset to gain a more accurate and clean surface representing the original dentition.³

Rapid Prototyping

For cases involving anterior teeth/esthetic zone, the next step would be to generate a new smile based on conventional dental methodologies at the correct vertical dimension, centric occlusion, and esthetic desires of the patient. Thus, there may be three sets of data: CBCT data, the digitized original state of the dentition, and a diagnostic wax-up or virtual tooth set-up representing the desired restorative result. However, this may not be all of the information needed; the digitization process can also include overlays of the patient's face, lips, and smile line to further refine the diagnostic process.

The development of additional software applications, such as Digital Smile Design (DSD Planning, digitalsmiledesign.com), has incorporated not only still images but also video to help analyze and transform smiles for either a porcelain laminate veneer case or an implant-supported restoration.⁴ DSD "ethically involves the patients in the restorative or smile enhancement process, making them the co-designer of their own treatment by sharing objectives, expressing their desires and expectations with the restorative team. The interaction between patient and dental specialist is improved by photos and videos taken at several steps of the treatment."⁵ Clinicians then must appreciate how to transfer the "virtual smile design" from their LCD monitor or tablet computer to the patient.

"Rapid prototyping," a concept that has been applied mainly to big industry, is gaining traction in dentistry. Many clinicians involved in implant dentistry and guided surgery applications are at least somewhat familiar with the term "stereolithography." Stereolithography is "a technique or process for creating three-dimensional objects, in which a computer-controlled moving laser beam is used to build up the required structure, layer by layer, from a liquid polymer that hardens on contact with laser light" (Oxford Dictionary). Thus, the process is one that adds material (additive), which differs from a "subtractive" process that removes material as with milling. This additive process is generally referred to as "3D printing," which until recently was impractical or cost-prohibitive for routine dental practices. The proliferation of low-cost 3D printers has become another major catalyst for many dental laboratories and practitioners who have taken the digital workflow to new levels by printing models for orthodontics, oral surgery, restorative dentistry, and production of nightguards, occlusal orthotic devices, and guided implant surgical templates, and much more.

Regardless of which 3D printer is used, however, an accurate 3D dataset representing the shape to be fabricated is required. This data can come from an intraoral scanner, a desktop optical scanner, CBCT, singularly or in combination, managed using appropriate software to produce the desired outcome. This process has become the foundation of the dental digital universe via the standard triangulation language (STL) file, ie, the data that is "exported" from the optical-scan software application.

The Digital Workflow

Regardless of the current technological advances, it is difficult for clinicians to remain totally within the digital workflow without using some analog component. The workflow starts with the initial patient visit, during which the original clinical presentation is captured with a video or still photograph. Today, this can be accomplished using a smart phone, all digitally. If dental implants, crown and bridgework, or porcelain laminate veneers are needed, it will be necessary and desirable to capture the pre-existing intraoral condition with either an analog impression or intraoral digital scan. However, as previously stated, a physical impression or poured stone cast will require conversion to a digital or STL file.

The next step is crucial to the ultimate success of any case: the diagnosis and treatment planning phase through a "merging" of technology combining the skills of both the clinician and dental laboratory technician. This merging of the different datasets with sophisticated software applications provides the foundation for success. To accomplish these tasks, clinicians and laboratory technicians must have the technical knowledge of the software applications available today. Whether a CAD/CAM restoration for a natural tooth preparation or a surgical guide for implant placement is being created, digital tools have forever changed the workflow.

With the advent of CAD/CAM for the fabrication of everyday crown-and-bridge dentistry, implant superstructures, bar overdentures, and much more, the lost-wax casting method has largely been replaced. Additionally, the continued development of new and improved materials has led to strong, esthetic, long-lasting restorations fabricated with a subtractive process facilitated by large laboratory-based milling machines. Smaller in-office milling machines, combined with highly accurate intraoral scanners, have helped to bring the process directly to the clinician's private office, providing state-of-the-art digital workflow for faster design and fabrication of patient-specific restorations.

There is a huge difference between printing a word-processing document from a computer to a laser printer, ie, from the computer screen to a physical piece of paper, and creating a smile design or surgical template for implant placement that was generated through either 3D printing or CAD/CAM modalities. It is not quite that simple. Understandably, some apprehension exists that all of this technology relies too much on computers and not enough on the skill of the clinician or technician. Dentists and dental laboratory technicians typically like to work with their hands, a main rationale for having chosen their profession. The digital universe requires knowledge, behavioral change, different skill sets, and time to master the technology. As dentistry continues to move from an analog to a digital workflow, it may be time to evaluate the state of the art and realize that it is not the computer that makes the decisions-it's only a tool to help clinicians make better decisions and improve their outcomes.⁶

About the author

Scott D. Ganz, DMD

Editor-in-Chief, Cone Beam International Magazine; Associate Editor, BMC Oral Health, Digital Dentistry Section; Private Practice, Maxillofacial Prosthetics and Implant Dentistry, Fort Lee, New Jersey

Reference

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2. Orentlicher G, Goldsmith D, Horowitz A. Applications of 3-dimensional virtual computerized tomography technology in oral and maxillofacial surgery: current therapy. J Oral Maxillofac Surg. 2010;68(8):1933-1959.

3. Ganz SD. Three-dimensional imaging and guided surgery for dental implants. Dent Clin North Am. 2015;59(2):265-290.

4. Coachman C, Calamita MA, Sesma N. Dynamic documentation of the smile and the 2D/3D digital smile design process. Int J Periodontics Restorative Dent. 2017;37(2):183-193.

5. What is Digital Smile Design (DSD). Digital Smile Design (DSD) website. https://www.digitalsmiledesign.com/about-dsd/. Accessed June 11, 2018.

6. Ganz SD. Brain-guided implant reconstruction: who makes the decisions? CAD/CAM Int J Digital Dent. 2017;8(3):26-31.