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Quality Resource Guide MetLife designates this activity for 1.0 continuing education credit for the review of this Quality Resource Guide and successful completion of the post test. FIRST EDITION Digital Dental Impressions Educational Objectives Following this unit of instruction, the practitioner should be able to: 1. Understand the history of digital impression systems. 2. Describe the basic function of a digital impression system. 3. Discuss new developments in equipment and software for digital impression systems. 4. Recognize evolving clinical applications for digital systems in a dental office. 5. Compare digital impressions to conventional impressions relative to clinical technique and accuracy. Introduction A key clinical process for any general dentist is the ability to accurately replicate the patient’s intraoral condition. Dentists do this routinely for diagnostic as well as therapeutic procedures. This has traditionally been accomplished with conventional impression materials that are placed in a gel or puttylike consistency using a tray, set in a manageable time, and have physical properties that maintain the accuracy of the impression when poured in stone for the model. This clinical workflow to produce a stone model relies on proper handling of several materials and processes that may result in distortions leading to inaccurate models. The application of digital impressions to replicate the patient’s intraoral condition attempts to improve the accuracy, efficiency, and workflow. History D r. Francois Duret presented his thesis titled “Optical Impressions” in France in 1973. It may be the earliest description of digital technology applied to dentistry. He went on to develop and patent a Computer-Assisted Design/Computer-Assisted www.metdental.com Machining (CAD/CAM) device for dentistry in 1984. The first marketed application of a digital impression approach for restorative dentistry was in the early 1980’s by Dr. Werner Mormann, a Swiss dentist, and Marco Brandestini, an Italian electrical engineer. Siemens Dental marketed the concept in 1987 as the CEREC System.1,2 Digital impression systems are based on CAD/CAM technology, which generally consists of three distinct steps or processes. Several articles have described the process in considerable detail.3-6 The process is initiated by using a camera or scanner to record the patient’s intraoral condition to a computer. A software program is used to manage the digital file and design the size and contour of the final restoration or appliance. The last step is to transmit the digital design file to a milling chamber for production of the final restoration or appliance. There are a variety of digital systems in the dental marketplace that apply the CAD/CAM process. One way to categorize these systems is to separate them into Digital Impression systems and Chairside CAD/ CAM systems. Each system relies on the ability to digitally record the intraoral condition in the dental office setting using a camera or scanner. What distinguishes the various systems is how the data is managed once it has been recorded in the dental office. Digital impression systems focus on the first step of the CAD/CAM process - recording the intraoral condition to a computer program. The primary focus of a digital impression software program is to identify and manage the digital file as it is electronically transferred out of the dental office for fabrication of the desired restoration or appliance. The Chairside CAD/CAM systems apply all three steps of the CAD/CAM process in the dental office in a technique to deliver the restoration in a single appointment. This Quality Resource Guide will focus on Digital Impressions; a companion QRG will discuss Chairside CAD/CAM systems. (Table 1 summarizes the available digital impression systems). Author Acknowledgements Dennis J. Fasbinder, DDS ABGD Cinical Professor, and Director of the Computerized Dentistry Program University of Michigan School of Dentistry Private Practice, Ann Arbor, Michigan Dr. Fasbinder has no relevant financial relationships to disclose. The following commentary highlights fundamental and commonly accepted practices on the subject matter. The information is intended as a general overview and is for educational purposes only. This information does not constitute legal advice, which can only be provided by an attorney. © Metropolitan Life Insurance Company, New York, NY. All materials subject to this copyright may be photocopied for the noncommercial purpose of scientific or educational advancement. Published December 2014. Expiration date: December 2017. The content of this Guide is subject to change as new scientific information becomes available. MetLife is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. Concerns or complaints about a CE provider may be directed to the provider or to ADA CERP at www.ada.org/goto/cerp. Accepted Program Provider FAGD/MAGD Credit 11/01/12 - 12/31/16 Address comments to: [email protected] MetLife Dental Quality Initiatives Program 501 US Highway 22 Bridgewater, NJ 08807 Quality Resource Guide – Digital Dental Impressions 1st Edition Table 1 - Dedicated Digital Impression Systems System True Definition Scanner iTero Intraoral Digital Scanner TRIOS Scanner Apollo DI IOS FastScanI Manufacturer 3M ESPE 2006 as Lava COS Align Technology, Inc. 2007 3Shape 2010 Sirona Dental IOS Technologies Inc 2010 Camera 3D in motion; Active wave front sampling – first video capture Parallel Confocal Imaging Technique Principle of Confocal Microscopy LED Video Active triangulation scanning. Hold wand still and camera moves within the wand. Reflective Powder Yes No No Yes No Monitor (virtual models) Monochromatic Touch screen Color RealColor scans Monochromatic Touch Screen Monochromatic Orthodontic Application Yes Invisalign Unitek Yes Invisalign Requires add-on module Yes Clear Correct Yes Orchestrate (model storage and removable appliances) Implant Application Yes Straumann Biomet 3i Yes Dentsply Zimmer Yes Yes Yes Glidewell Lab Early digital scanners utilized a process of recording overlapping single images that were stitched together by the computer software to create larger models. The number of images recorded, the speed of recording, and the size of the data file were greatly influenced by the graphics capability and processing speed of computers. The ability to process much larger digital files improved as computer processors evolved, resulting in increased quantity of images as well as the current trend to move to video data files. The first clinical application developed for digital impression systems was to fabricate single tooth restorations (inlays, onlays, veneers, and crowns). As the systems have advanced, additional applications have been implemented including diagnostic planning, orthodontic treatment planning and appliance fabrication, implant planning, surgical guide fabrication, abutment design and fabrication, and applications for removable appliances. www.metdental.com Digital Cameras and Scanners C urrently marketed scanners rely on a number of imaging technologies confocal microscopy, optical coherence tomography, stereovision, triangulation, and interferometry. A more detailed engineering discussion of these technologies as they apply to recording intraoral images may be found in Logozzo and coworkers publication.7 One common concern of many dentists is the size of the camera used for scanning. Most manufacturers have trended towards cameras approaching the size of dental handpieces assuming that dentists are very comfortable using handpieces intraorally and a camera of similar size would be able to be applied in a familiar and comfortable fashion. In general, this may seem like a good idea, however the size of the camera is also an ergonomic concern. Similar to curing lights, the entire camera does not need to fit in the mouth, only the working tip of the camera. Although a small sized camera head is an obvious advantage for intraoral access, the ergonomics of the camera body may be a greater influence on the ease of intraoral scanning since it has a direct impact on the maneuverability of the camera. Digital Impressions Compared to Conventional Impressions T he workflow for a conventional impression using elastomeric materials includes a series of procedures that must be properly managed to ensure accuracy. This includes proper mixing and placement of the impression material, proper disinfection and handling prior to model fabrication, proper measuring and handling of stone when pouring the model, and proper recovery of the model from the impression. These procedures are not without problems and limitations, however they have been managed by most dentists to provide accurate replicas of the intraoral condition for decades. One significant limitation of the conventional method Page 2 Quality Resource Guide – Digital Dental Impressions 1st Edition is the degradation of accuracy when multiple pours are made in the same impression. Digital impressions obviously avoid many of the potential problems of conventional impressions with the added advantage that models can be fabricated with equal accuracy an unlimited number of times as the digital file does not go through any sort of accuracy degradation as it is repeatedly processed. A common challenge with all impression techniques is their ability to accurately capture subgingival margins. There are several essential principles that the clinician must abide by to make an accurate digital impression. The clinical area to be impressed must be free of debris, isolated from blood or moisture, and soft tissues need to be retracted from the preparation margins and tooth contours. These principles equally apply to both conventional and digital impressions. As much as clinicians would like to record preparation margins and tooth contours through soft tissues, blood, or moisture, this is not currently possible. Digital scanners are line-ofsight recorders. The scanner or camera can only record what is visible to the lens. Structures or surfaces obscured by debris, fluids, or soft tissues are also obscured from being accurately recorded in much the same way they are for conventional impressions. However, there are advantages to digital impressions in regions difficult to impress because of soft tissue interference or moisture. Sometimes clinicians remove a conventional impression from the mouth only to find there is a small bubble or tear at a critical margin. The only way to correct this deficiency is to redo the entire process and remake the impression. Some digital impression scanners offer the opportunity to “correct” or modify existing images without the need to redo the entire impression. Sections of the scan can be deleted from the virtual model and that small section rescanned and added to the existing virtual model saving considerable time and discomfort for both the dentist and patient. Evaluation of the accuracy of a conventional impression is a critical decision in the dental office as it determines the ultimate accuracy of www.metdental.com the final restoration. Many times discrepancies are not identified until the model has been fabricated. With conventional impressions this occurs well after the patient has left the dental office, with no opportunity to immediately correct the discrepancy. Digital impressions offer the opportunity to evaluate the impression immediately after scanning by magnifying it 20X on the computer monitor. This aids detection of discrepancies while the patient is still in the chair with the potential to correct them immediately. Digital systems do not record the “occlusion” from the opposing arch but rather record the 3D shape of the opposing teeth and then virtually mount them against the preparation and adjacent teeth. The software program is able to detect the areas of contact between the two virtual models similar to articulating paper detecting contact points between opposing mounted stone models. The digital mounting also has the advantage of detecting degrees of contact or intersection to help in developing the desired occlusal contact points and lateral interferences. Advantages and Disadvantages of Digital Impressions See Table 2. Accuracy of Digital Impressions I t is a well-accepted principle that the accuracy of a dental restoration or appliance can only be as good as the accuracy of the impression, be it conventional or digital. Digital impressions have been shown to be at least as accurate as conventional impressions and often times, more accurate. An in vitro study compared the accuracy of models made from full arch conventional and digital impressions.8 Master models were repeatedly scanned with the Lava COS system and impressed repeatedly with polyvinylsiloxane impression material to fabricate replica models. The accuracy of the replica models was measured with a computer graphic analysis program. There was no significant difference in the accuracy of the replica models compared to the master models using either impression technique. Table 2 - Advantages and Disadvantages of Digital Impressions Advantages of Digital Impressions • Less patient chair time required; increased clinical efficiency • No need for distasteful impression materials potentially leading to gagging • More comfortable impression process for the patient, creating less anxiety • Technology tends to be engaging for a patient and provides evidence of state-ofthe-art care • Indefinite electronic storage - with less space needed • Eco-friendly aspects include eliminating the need for disposable plastic trays and impression materials - digital impressions are disposed of with the “delete” button • Distortion-free model remakes possible indefinitely since the original file is available for repeated model processing • Able to detect preparation undercuts and/or inadequate preparation reduction prior to transmitting case to the lab with the potential to correct the problems during the same appointment. Disadvantages of Digital Impressions • Increased initial capital investment for equipment • Unknown length of time digital files will be able to be managed because of future developments in software • Infection control procedures for the scanner are more time consuming Page 3 Quality Resource Guide – Digital Dental Impressions 1st Edition Another in vitro study reported the marginal and internal fit of a Fixed Partial Denture (FPD) fabricated from conventional and digital impressions.9 An acrylic master cast with prepared abutment teeth for a FPD from #19 to #21 was fabricated. CAD software was used to measure margin gap, internal adaptation, and cervical discrepancies between the FPDs. The marginal gap was not significantly different between conventional and iTero digital impressions with the internal and cervical discrepancies less for the digital impressions. Another in vitro study evaluated the accuracy of digital impressions and conventional impressions using the Lava COS scanner, polyether impressions, and digital scanning of the models made from the polyether impressions.10 The digital impression made with the Lava COS scanner had significantly higher accuracy compared to conventional impressions and indirect scanning of the models. Another study compared the clinical fit of crowns made from digital and conventional impressions.11 A digital impression using the Lava COS system and one conventional silicone impression was made of the same crown preparation in each of 20 patients. Duplicate zirconia crowns were fabricated from each impression. Margin fit for each crown was measured intraorally at the time of crown delivery using a replica technique. Crowns fabricated with the digital impression technique had a significantly better margin fit (49 microns) than those made from a conventional impression (71 microns). One randomized clinical study compared the margin fit of two types of zirconia crowns made with conventional impressions and digital impressions.12 A conventional polyvinylsiloxane impression and a digital impression with the Lava COS system were made for each of fifty crown preparations. Crowns were made for each preparation using the two impression techniques. Each crown was measured intraorally for margin fit and internal adaptation using a replica technique. The crowns made with the digital impression had a significantly better margin fit (51.45 + 18.59 microns) than those made with a conventional impression technique (78.62 + 25.62 microns). www.metdental.com A more extensive in vitro study compared the accuracy of ceramic crowns from different digital impression systems and types of conventional impression techniques.13 Conventional impressions were made of a single crown preparation on a master model using 2-step and single step, puttywash impression techniques. Digital impressions were made of the master model crown preparation using the Lava COS, CEREC AC, and iTero digital systems. The mean margin fit of crowns was 48 + 25 microns for Lava COS, 30 + 17 microns for CEREC AC, 41 + 16 microns for iTero, 33 + 19 microns for single-step putty wash technique and 60 + 30 microns for the two-step putty wash technique. The mean internal fit was 29 + 7 microns for Lava COS, 88 + 20 microns for CEREC AC, 50 + 2 microns for iTero, 36 + 5 microns for single-step putty wash technique, and 35 + 7 for two-step putty wash technique. There was no significant difference in the margin fit or internal adaptation of the crowns using any of the techniques. Clinical Application T he learning curve for digital impression systems is significantly less than for chairside CAD/CAM systems. The digital impression is transferred to a laboratory where the restoration is fabricated so there is no software design functions or milling functions for the clinician to master. Development of two primary skills is necessary to become proficient in making digital impressions. One is learning to make the appropriate rotational and translational movements with the scanner in the mouth to record the intraoral condition. The second is management of the administrative functions of the software program to identify the case, complete the electronic prescription, and electronically transmit the case to sites outside the dental office. Companies marketing a digital impression system manage the cloud computing functions of digital file distribution to the locations requested by the dentist. The company establishes the electronic connection through conventional Wi-Fi equipment when the system is installed in the dental office. Protection of patient privacy is an obvious concern with the proliferation of digital systems. Manufacturers of digital systems have developed HIPPA-compliant safeguards and encryption process to protect the transmission of digital data from the dental office to the dental laboratory. However, the WiFi safeguards in place at the clinical setting also significantly contribute to the final HIPPA-compliant safeguards for data transmission. This should be evaluated during discussions prior to installation with the digital system manufacturer representative. The most common application of digital impressions is the fabrication of dental restorations. There are two distinct workflows that may be used. One option is to transmit the digital file to the dental laboratory where they process a model similar to what would be done with a conventional impression. Companies generally have selected specific model processing applications for their digital impression systems, but the digital files may also be used to process alternative types of models such as milled polyurethane, printed resin, or resin stereolithography (SLA). Once the model is fabricated, any standard laboratory procedure may be used to develop and create the dental restoration. The second alternative is to input the digital file to a CAD program to design the desired substructure or full contour restoration. Once the design has been milled, the restoration can be finalized using the processed model. A number of labs also process “model-free” restorations using the full contour design from the CAD program in a cost effective and efficient workflow. The dental laboratory generally selects the technique based on specifics of the case and the type of restoration requested as well as the capabilities of the laboratory. Orthodontic Applications A s the ease and efficiency of recording full arch scans has improved, orthodontic applications for digital impressions have significantly increased. Digital files are used for orthodontic diagnosis and treatment planning, case documentation, as well as appliance design and fabrication. Of particular interest to orthodontists is the ability to electronically store case documentation electronically rather than committing significant storage areas to cataloging models and boxes. Page 4 Quality Resource Guide – Digital Dental Impressions 1st Edition Implant Applications A nother rapidly developing clinical application for in-office digital impressions is dental implant therapy. There are two main clinical applications. One application is in implant case planning. Planning the implant location based on the desired parameters of the final restoration is a very desired approach. Cone Beam Computer Tomography (CBCT) has developed into a preferred 3D diagnostic tool for optimizing the surgical placement of implants. Commercial software programs are available to combine the intraoral digital impression with the CBCT file for planning of the implant case as well as fabrication of surgical guides based upon the planned outcome. A number of dentists use fixture level impressions with elastomeric materials to record the 3D position of the implant in the alveolus for laboratory fabrication of custom abutments and implant retained restorations. The stone model and implant analogue is scanned in the laboratory using a bench-top scanner to design the desired abutment and restoration. Digital impression systems can now significantly streamline this workflow with the use of encode abutments or scan bodies to record intraoral fixture level digital impressions of implants. They contain unique surface geometry or markings that allow the software to specifically align the implant in 3D within the virtual model. The digital fixture level impression is transmitted to the dental laboratory for design and fabrication of the custom abutment and final restoration. Conclusion D igital impression systems based on CAD/CAM technolgy are developing at an ever-increasing rate. Initial restorative applications have now expanded to include both diagnostic and therapeutic applications in orthodontic, implant, and removable prosthodontics with new collaborations between companies promising additional applications. As the technology continually evolves, dentists will discover their own level of comfort and involvement with digital impression systems to incorporate the new applications into their dental offices. REFERENCES 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. uret F, Preston JD. CAD/CAM imaging in dentistry. Curr Opin Dent 1991;1(2):150-154. D Mormann WH, Brandestini M, Lutz F, Barbakow F. Chairside computer-aided direct ceramic inlay. Quintessence Int 1989;20(5):325-339. Beuer F, Schweiger J, Edelhoff D. Digital dentistry: An overview of recent developments for CAD/CAM generated restorations Br Dent J 2008;204(9):505-11 Birnbaum NS, Aronson HB. Dental impressions using 3D digital scanners: Virtual becomes reality. Compend Contin Educ Dent. 2008;29(8):494505. Fasbinder DJ Digital dentistry: Innovation for restorative treatment. Compend Contin Educ Dent 2010;31(SI4):2-11. Fasbinder DJ. Using digital technology to enhance restorative dentistry. Compend Contin Educ Dent 2012;33(9):666-677. Logozzo S, Franceschini G, Kilpelä A, Caponi M, Governi L, Blois L.A comparative analysis of intraoral 3D digital scanners for restorative dentistry. Internet J Med Tech 2008 Volume 5 Number 1. Ogledzki M, Wenzel K, Doherty E, Kugel G. Accuracy of 3M-Brontes stereolithography models compared to plaster models. J Dent Res 2010;89(SI A):abstract #1060. Svanborg P, Skjerven H, Carlsson P, Eliasson A, Karlsson S, Ortorp A. Marginal and internal fit of cobalt-chromium fixed dental prostheses generated from digital and conventional impressions. Int J Dent 2014;2014:534382. doi: 10.1155/2014/534382. Epub 2014 Mar 3. Guth JF, Keul C, Stimmelmayr M, Beuer F, Edelhoff D. Accuracy of models obtained by direct and indirect data capturing. Clin Oral Invest 2013;17:1201-1208. Syrek A, Reich G, Ranftl D, Klein C, Cerny B, Brodesser J. Clinical evaluation of all-ceramic crowns fabricated from intraoral digital impressions based on the principle of active wavefront sampling. J Dent 2010 38(7):553–559. Fasbinder DJ, Neiva GF, Dennison JB, Heys D, Heys R. Evaluation of zirconia crowns made from conventional and digital impressions. J Dent Res 2012;91(SI A): abstract #644. Seelbach P, Brueckel C, Wöstmann. Accuracy of digital and conventional impression techniques and workflow. Clin Oral Invest 2013;17(7):17591764. www.metdental.com Page 5 Quality Resource Guide – Digital Dental Impressions 1st Edition POST-TEST Internet Users: This page is intended to assist you in fast and accurate testing when completing the “Online Exam.” We suggest reviewing the questions and then circling your answers on this page prior to completing the online exam. (1.0 CE Credit Contact Hour) Please circle the correct answer. 70% equals passing grade. 1.What three sequences are included in a CAD/CAM process? a. Image recording, computer design, 3D printing b. Image recording, lab design, Subtractive milling c. Video recording, computer design, 3D printing d. Image recording, computer design, Subtractive milling e. Video recording, lab design, 3D printing 2.What was the first marketed CAD/CAM system? a. Duret Optical Impression system b. Siemen Scanner c. CEREC System d. Ceramic Reconstruction System e. E4D System 3.What process did the first intraoral scanner use to create virtual models in the software program? a. Computer stitching of overlapping single images b. Video recording c. Model extrapolation from single images d. Subtractive image recording e. Image database copying 4.What is the difference in using conventional PVS impression materials and digital impressions to record subgingival margins? a. Conventional PVS impression materials can record deeper subgingival margins. b. Both techniques require equally good tissue retraction and moisture isolation. c. Digital impressions can record deeper subgingival margins. d. Conventional PVS impressions deflect soft tissues better than digital impressions. 5.What is the outcome of most in vitro research studies that compare conventional PVS impressions to digital impressions relative to margin accuracy? a. There is no real difference in accuracy between conventional PVS and digital impressions b. Conventional PVS impressions are more time consuming, but more accurate c. Digital impressions are generally more accurate than conventional PVS impressions d. Conventional PVS impressions using a light body material are more accurate than digital impressions e. Only a limited number of digital impression systems are able to consistently record accurate preparation margins www.metdental.com 6.Digital Impression systems focus on which step of the CAD/CAM process? a. Image recording b. Laboratory computergraphic design c. In-office milling d. Computer Assisted Design e. 3D printing 7. What significant advantage does a Digital Impression system offer for orthodontic applications? a. Digital diagnosis b. Predictive case planning c. Post-treatment retainer printing d. Digital model archiving e. More efficient diagnostic models 8.What significant advantage does a Digital Impression system offer for implant applications? a. Clinical and laboratory streamlining of the 3D recording of the implant in the alveolus b. Integration of the digital recording with dicom files of CBCT c. Design and fabrication of surgical guides d. Design and fabrication of temporary restorations e. Case documentation 9.Which of the following is not a Digital Impression system? a. True Definition (3M ESPE) b. Apollo DI (Sirona Dental) c. TRIOS (3Shape) d. iTero (Align Technology) e. Duret Scanner (Begio) 10.Which of the following is not a disadvantage of Digital Impression Systems? a. Increased initial capital investment for equipment b. Unknown length of time digital files will be able to be managed because of future developments in software c. Infection control procedures for conventional impressions are more time consuming d. The learning curve is more involved for digital impressions e. More preventive maintenance of equipment Page 6 REGISTRATION/CERTIFICATION INFORMATION (Necessary for proper certification) Name (Last, First, Middle Initial):______________________________________________________________ PLEASE PRINT CLEARLY Street Address:_________________________________________________ Suite/Apt. Number_________ City: ____________________________________ State:_______________ Zip:____________________ FOR OFFICE USE ONLY Telephone: ____________________________________ Fax:____________________________________ Date of Birth:___________________________________ Email: __________________________________ State(s) of Licensure:_____________________________ License Number(s):_________________________ Preferred Dentist Program ID Number:___________________________ AGD Mastership: Yes No AGD Fellowship: Yes No Date:______________ Please Check One: General Practitioner Specialist Check Box If Not A PDP Member Dental Hygienist Other Quality Resource Guide – Digital Dental Impressions 1st Edition Providing dentists with the opportunity for continuing dental education is an essential part of MetLife’s commitment to helping dentists improve the oral health of their patients through education. You can help in this effort by providing feedback regarding the continuing education offering you have just completed. Please respond to the statements below by checking the appropriate box, using the scale on the right. 1 = POOR 5 = Excellent 1 2345 1. How well did this course meet its stated educational objectives? 2. How would you rate the quality of the content? 3. Please rate the effectiveness of the author. 4. Please rate the written materials and visual aids used. 5. The use of evidence-based dentistry on the topic when applicable. 8. The level to which your personal objectives were satisfied. 9. Please rate the administrative arrangements for this course. 6. How relevant was the course material to your practice? 7. The extent to which the course enhanced your current knowledge or skill? 10. How likely are you to recommend MetLife’s CE program to a friend or colleague? (please circle one number below:) 10 9 8 7 6 extremely likely 5 4 neutral 3 2 1 0 not likely at all What is the primary reason for your score? 11. Please identify future topics that you would like to see: Thank you for your time and feedback. To Complete Program Traditionally, Please Mail Your Post Test and Evaluation Forms To: MetLife Dental Quality Initiatives Program 501 US Highway 22 Bridgewater, NJ 08807 www.metdental.com N/A