The workflow at the dental office is rapidly changing to a more efficient and cost effective chain that is using state of the art technology (Joda and Brägger, 2015). Computer generation of dental records, computer assisted imaging techniques and virtual treatment planning have changed the way dentistry is practiced. Digitalisation has been adopted in the 3 major steps of the conventional patient workflow resulting in three processes:
Digital patient: the patient data is digitized which includes the clinical information, x-ray-based information or casts.
Virtual patient: digital treatment planning and on-screen simulation can assist in the patient’s rehabilitation.
Real patient: computer aided manufactured devices using milling or 3d printing technology can assist in treatment procedures.
This digital treatment workflow can be applied to all fields of dentistry or dentomaxillofacial practice but is most advanced in implant and restorative dentistry (Joda and Brägger, 2015).
Virtual implant simulations based on Computed Tomography (CT) volumetric data had been introduced with the ability to create surgical templates for the placement of implants. The use of such 3D interactive planning has help reduce treatment complications by improving accuracy of placement (Vandenberghe, 2018).
More advanced planning can be achieved by using radiographic guides and visualizing the prosthetic outcome virtually. This data can then be transferred to a CAM unit to produce a surgical template that can assist in precise implant surgery. Since the advent of Cone Beam Computed Tomography (CBCT), the 3d virtual planning of implant restorations has become popular and by combining the CBCT data with digital impressions, guided implant surgery has become precise and readily accepted (Lanis and Álvarez Del Canto, 2015).
Digital impression taking of teeth preparations, has allowed the speedy design and production of dental restorations. With the introduction of CAM materials, laboratory procedures have become more efficient and immediate. Hence, there are reduced number of visits which makes it more comfortable for the patient. In addition, the final aesthetic outcome maybe more predictable.
Virtual set-ups using digital models with on-screen simulation of orthodontic treatment are being used in Orthodontic practice. The on-screen simulations have been found to be as accurate as conventional set-ups. Virtual planning provides advantages over traditional panning, for efficient storage, digital manipulation with reduction of errors and the ability to superimpose the stages of treatment at different time intervals. The transfer of planning using guide and aligners, customized computer – manufactured appliances, guided piezo-assisted surgery or guided tooth transplantation may provide a more precise and predictable outcome (Strbac et al., 2016).
Digital Workflow for Implant Dentistry
It is a workflow in which every phase of the diagnosis, plan and treatment is going to be conducted by a digital resource.
The complete digital workflow is composed of various digital technologies, with both hardware and software, material science and dental technology.
Digital workflow is based around three elements
- Data Acquisition
- Data Processing with CAD/CAM
- Lab, surface veneering processes
Implant procedures are one of the most exciting facets of dentistry that has been enhanced by digital technology. The innovations explored provide clinicians with the tools for diagnosis, planning, placement and restoration of implants in a more progressive way — one that is quickly becoming the standard of care (Almeida e Silva et al., 2014).
Data Acquisition
Imaging is a mere representation of an objects form through visual images. Digitalisation includes any device capable of converting analogue signals to digital signals. In dentistry, ionizing radiation is used when visualizing the anatomical or pathological structures within the patient. The most common radiation equipment used in dentistry is a CBCT, the output file is a DICOM file which can be processed by most software. The 3d facial profile can also be captured with a 3d camera. The output from a dental 3d camera is a STL file. The out from a CBCT and a 3D camera can be combined and used for surgical cosmetic data. Dental hard and soft tissue can be captured directly with intra oral scanners or indirectly by scanning a physical dental model by a laboratory model scanner.
The intra oral scanners can allow for standardizing dental impression taking in difficult cases such as full arch scans and including edentulous arches. The precision and accuracy of intra oral scanners are variable depending on the brand (Seelbach et al., 2013).
The use of a CBCT and intra oral digital impression together with additional guided software a clinician can virtually plan the treatment for the placement of implants according to the patient’s anatomical structures and case plan. The type and size of the planned implant, its position within the bone and its relationship to the planed restoration and adjacent teeth or implants are predetermined before performing the surgery on the patient. A surgical drill guide is fabricated after this process which is used by clinicians to place the planned implants in the same position as the treatment was planned virtually. This allows for more accurate and predictable implant placement.
The benefits of a CBCT and digital impressioning includes increased accuracy and safety, higher level of precision, it is faster and more comfortable, it is less invasive, and the surgical procedure is quicker with a speedy recovery due to less pain, swelling and bruising (Seelbach et al., 2013).
Data Processing with CAD/CAM
Computer-aided design (CAD) and computer-aided manufacturing (CAM) have become a popular aspect of dentistry for the past two decades (Davidowitz and Kotick, 2011).The technology, which is used in both the dental laboratory and the dental office, can be applied to inlays, onlays, veneers, crowns, fixed partial dentures, implant abutments, and even full-mouth reconstruction. CAD/CAM technology was developed to solve 3 challenges. The first was to ensure adequate strength of the restoration, especially for posterior teeth. The second was to create restorations with a natural appearance. The third was to make tooth restoration easier, faster, and more accurate. In most cases, CAD/CAM technology provides patients with same-day restorations.
Dentists and laboratories have a wide variety of ways in which they can work with the new technology. Dentists can take a digital impression and email it to a laboratory for fabrication of the restorations or they can do their own computer aided design and milling in-house.
When laboratories receive a digital impression, they can either create a stone model from the data and continue with traditional fabrication or rescan the model for milling. Alternatively, the laboratory can do all the design work directly on the computer based on the images received.
The use of CAD/CAM technology for dental restorations has numerous advantages over traditional techniques. These advantages include speed, ease of use, and quality. Digital scans have the potential to be faster and easier than conventional impressions because casts, wax-ups, investing, casting, and firing are eliminated (Davidowitz and Kotick, 2011). According to Sirona, half-arch impressions with the most recent version of CEREC take 40 seconds and full-arch impressions take 2 minutes (Sirona, 2008). CAD/CAM also makes design and fabrication faster; a full-contour crown takes just 6 minutes to mill.
An on-site milling machine means that patients can receive their final restoration the same day they come in, without making a second appointment and hence is time efficient.
Patients no longer need to have provisional restorations, which take time to fabricate and fit (Mormann et al., 1989). If anaesthetics are needed, they only need to be administered once. The quality of CAD/CAM restorations is extremely high because measurements and fabrication are so precise. In a study of 117 subjects by Henkel, each subject had 2 crowns made (Henkel, 2007). One crown was made based on physical impressions using standard trays and impression material and another was made based on electronic impressions. Without knowing which one was which, dentists chose the crown based on the electronic impression 68% of the time (Henkel, 2007). Perhaps this difference in the finished product should not be surprising, given the wide variation in quality of traditional impressions. Christensen stated in 2005 that he had seen impressions sent to laboratories in which more than 50% of the preparation margins were not discernible. Traditional impressions suffer from complications, such as air bubbles, impression drag ,tears in the impression material, cords or other debris fixed in the impression material, and missing teeth (Christensen, 2005).
CAD/CAM restorations have a natural appearance because the ceramic blocks have a translucent quality that is like enamel, and they are available in a wide range of shades (Mormann et al., 1989).Ceramic wears well in the mouth, even when it is used for posterior teeth. Its abrasiveness is like conventional and hybrid posterior composite resins, hence it causes minimal wear to the opposing teeth. The quality of prefabricated ceramic blocks is consistent, and they are free from internal defects. The computer program is designed to produce shapes that will stand up to wear.
Savings in time and labour have the potential to reduce costs, and the promise of faster, high-quality restorations should appeal to patients and patients are also happy to avoid the need for gag-inducing impressions.
A major advantage is that all the scans can be stored on the computer; whereas, stone models take up space and can chip or break if stored improperly (Birnbaum et al., 2009). Still, CAD/CAM systems have disadvantages. The initial cost of the equipment and software is high, and the practitioner needs to spend time and money on training. Dentists without a large enough volume of restorations will have a difficult time making their investment pay off. Just as with conventional impressions, in taking an optical scan the dentist needs to obtain an accurate recording of the tooth in need of restoration. The scan needs to emphasize the finish line and precisely duplicate the surrounding and occlusive teeth.
Digital scanning requires the same type of soft-tissue management, retraction, moisture control, and haemostasis like a conventional impression. Digital impression systems may not save time as they are currently used because of the need for multiple steps. For example, dentists who use certain scanners must first send the images for a clean-up process, which is followed by setting of the margins by a dental technician. The images next go to the clinician’s dental laboratory for review.
Lab Surface Veneering After CAM production the final veneering will be done by dental technicians. Materials involved are usually acrylic, porcelain work or surface stain only depending on prosthesis designs. DIAGNOSTIC WAX-UP The diagnostic wax-up is an essential component in implant treatment planning. The intraoral scan is merged with facial photos, in specialized laboratory or chairside software. This allows for a patient-specific digital wax-up and rapid prototyping of smiles without the patient being present. Multiple tooth shapes and sizes can be selected from a generic library, and the software lets clinicians and technicians visualize how the virtual wax-up will appear in the smile. This allows for prosthetically driven implant planning. On completion of the digital waxup, the patient can visualize the case prior to treatment, and adjustments can be made to tooth shape, size or morphology. When the final design is complete, the digital wax-up can be produced via 3D printing or milling and tried in the patient’s mouth (Ludlow et al., 2017). COMPUTER-GUIDED SURGERY Virtually placed implants have been carefully planned using the necessary merged information between the digital impression and CBCT to ensure they are at the ideal angulation, location and depth to support optimal prosthetic results (Ludlow et al., 2017) . During surgery, this planning is reassigned to the patient via a surgical guide, which is made with either an additive printing process or a subtractive milling process. Certain software platforms allow for in-office 3D printing or milling of surgical guides, while others require off-site fabrication depending on their system requirements. The benefits to the clinician and patient are significant, following the fabrication of the surgical guide. Using a computer-generated surgical template greatly reduces the chance for a positional error at the time of implant placement, compared to freehand surgery (Di Giacomo et al., 2005). There can be a 6% probability of a positional error using a computer guided template, and an 88% probability of having a positional error with a freehand approach (Arisan et al., 2013). These advantages of guided surgery allow greater precision in implant placement and increased restorative simplicity. The benefits of guided surgery affect both the dental provider and patient. Patients benefit by experiencing significantly less intraoperative and postoperative complications, such as pain and swelling. The benefit of not having to raise a flap for surgery and has been shown to be the preferable method for executing guided surgery with increased patient comfort. In addition to preserving periosteum contact with bone, blood supply and osteogenic potential it has been demonstrated that the flapless technique enhanced esthetics by preserving papilla (Cosyn et al., 2012). NAVIGATION (ROBOTIC) SURGERY Robotic surgery is implant placement with the use of navigation. This involves the use of tracking devices attached to the patient and implant handpiece which relate these 2 positions in virtual space whereby the data is a captured to a central processing unit and superimposed on a monitor. The relation to the virtually planned implant osteotomy is displayed, and the implant handpiece can be adjusted by following the onscreen graphics. Navigation surgery eliminates the need for a surgical template, as used in computer-guided surgery, and allows real-time correction of the osteotomy during the procedure (Ludlow et al., 2017). SCAN BODIES In the restorative phase of implant dentistry, digital impressions can also be applied. Intraoral scan bodies have been developed for most major implant brands, which allows the use of most intraoral scanning devices on the market. These different scan bodies allow for the implant brand, position and timing to be registered by digital impression and transferred to a digital model. All the necessary information relative to provisional treatment, opposing arch, and bite registrations can be captured with intraoral scanners. This workflow has proven to be efficient and accurate for dentate and edentulous cases (Joda et al., 2016). Digital techniques allow for quicker treatment times that benefit the patient and the clinician; furthermore, patients in one study unanimously preferred digital impressions over conventional impressions (Joda and Brägger, 2016). ABUTMENTS AND RESTORATION These digital impressions can be sent to a laboratory or remain in the scanning system for in-office fabrication of the final abutment and prosthetic. In advanced cases, most clinicians find it useful to work with a skilled dental laboratory. The dental technician can use sophisticated technology to design and manufacture the corresponding restorative components. Digital laboratory technologies reduce the number of error-inducing steps and manipulations of materials, and thus have been associated with more efficient processes. Custom abutments are designed digitally and milled out of the material of the clinician’s choice (Abduo J et al., 2016). The complex process of fabricating restorations has been simplified by these digital designs and manufacturing methods. Digitally designed and milled provisional restorations can be fabricated before the surgical procedure for immediate temporization. Digital workflow compared to a conventional workflow, has been shown to be three times more efficient for the formation of implant-supported crowns. Digital workflow also benefits the clinician, by reducing adjustment and seating time, making it faster than restorations fabricated with conventional methods. Conclusion When considering the many steps in the digital dental workflow, it can be concluded that digital imaging is one of the crucial steps in this process. Not only is it necessary for clinicians to understand the technological parameters of digital images, but it is as important to be able to manipulate these digital datasets and have knowledge on the possible pitfalls in the digital chain. While 3D low dose volumetric CBCT imaging and 3D intraoral optical impressions are rapidly becoming implemented in general dental practice, new applications for follow-up offer new potential in the maintenance of our patients. References ABDUO J, BENNAMOUN M, TENNANT M & J., M. 2016. Impact of digital prosthodontics planning on dental esthetics: Biometric analysis of esthetic parameters. J Prosthet Dent., 115, 57-64. ALMEIDA E SILVA, J. S., ERDELT, K., EDELHOFF, D., ARAÚJO, É., STIMMELMAYR, M., VIEIRA, L. C. & GÜTH, J. F. 2014. Marginal and internal fit of four-unit zirconia fixed dental prostheses based on digital and conventional impression techniques. Clin Oral Investig., 18, 515-523. ARISAN, V., KARABUDA, C. Z., MUMCU, E. & ÖZDEMIR, T. 2013. Implant positioning errors in freehand and computer-aided placement methods: a single-blind clinical comparative study. Int J Oral Maxillofac Implants, 190-204. BIRNBAUM, N. S., AARONSON, H. B., STEVENS, C. & COHEN, B. 2009. 3D Digital Scanners: A High-Tech Approach to More Accurate Dental Impressions. Inside Dentistry, 5. CHRISTENSEN, G. J. 2005. The state of fixed prosthodontic impressions: room for improvement. J Am Dent Assoc, 136, 343-346. COSYN, J., HOOGHE, N. & DE BRUYN, H. 2012. A systematic review on the frequency of advanced recession following single immediate implant treatment. J Clin Periodontol., 39, 582-589. DAVIDOWITZ, G. & KOTICK, P. G. 2011. The Use of CAD/CAM in Dentistry. Dent Clin North Am, 55, 559-570. DI GIACOMO, G., CURY, P. R., N.S., D. A., SENDYK, W. R. & SENDYK, C. L. 2005. Clinical application of stereolithographic surgical guides for implant placement: preliminary results. J Periodontol, 76, 503–507. HENKEL, G. L. 2007. A comparison of fixed prostheses generated from conventional vs digitally scanned dental impressions. Compend Contin Educ Dent, 28, 422–4, 426–8, 430–1. JODA, T. & BRÄGGER, U. 2015. Digital vs. conventional implant prosthetic workflows: a cost/time analysis. Clinical Oral Implants Res., 26, 1430-1435. JODA, T. & BRÄGGER, U. 2016. Patient-centered outcomes comparing digital and conventional implant impression procedures: a randomized crossover trial. Clin Oral Implants Res., 27, e185–e189. JODA, T., LENHERR, P., DEDEM, P., KOVALTSCHUK, I., BRAGGER, U. & ZITZMANN, N. 2016. Time efficiency, difficulty, and operator’s preference comparing digital and conventional implant impressions: a randomized controlled trial. Clin Oral Impl Res. LANIS, A. & ÁLVAREZ DEL CANTO, O. 2015. The combination of digital surface scanners and cone beam computed tomography technology for guided implant surgery using 3Shape implant studio software: a case history report. International J. Prosthodontics, 28, 169-178. LUDLOW, M., RENNE, M. S. & RENNE, W. 2017. digital-workflow-for-implant-dentistry. Decisions in Dentistry, 3, 13-17. MORMANN, W. H., BRANDESTINI, M., LUTZ, F. & BARBAKOW, F. 1989. Chairside computer-aided direct ceramic inlays. Quintessence Int, 20. SEELBACH, P., BRUECKEL, C. & WOSTMANN, B. 2013. Accuracy of digital and conventional impression techniques and workflow. Clinical Oral Investigations, 17, 1759-1764. SIRONA. 2008. The CEREC Acquisition Center powered by Bluecam [Online]. http://www.cereconlin.com/cerec/acquisition-center.html. [Accessed]. STRBAC, G. D., SCHNAPPAUF, A., GIANNIS, K., BERTL, M. H., MORITZ, A. & ULM, C. 2016. Guided autotransplantation of teeth: a novel method using virtually planned 3-dimensional templates. Journal of Endodontics, 42, 1844-1850. VANDENBERGHE, B. 2018. The digital patient-Imaging science in dentistry. Journal of Dentistry, 74, 21-26.