Digital Impressions and In-Office CAD/CAM: A Review of Best Practices and What's to Come

Then and Now

The use of intraoral scanners to take digital impressions is nothing new to the field-the first intraoral scanners were developed in the early 1980s, and their use has increased steadily since.¹ Digital impression scanning offers a range of benefits to the dentist and the patient, from the speed by which a digital scan can be taken to the elimination of uncomfortable trays and plasters. Digital impressions simplify what used to be a multistep process and are capable of yielding accuracy that matches or exceeds other methods when the scanning is performed correctly.²

Best Practices

As with traditional impression-taking, successfully obtaining a clear and accurate scan relies on the skill of the dentist, but the technology built into today's intraoral scanners helps obtain the clearest impressions possible. Scanner technology has advanced exponentially from previous years. Today's models not only take great impressions, but they also offer information about everything from missed areas in the scan to data that aids in the diagnostic process. For example, a current state-of-the-art system (iTero Element^® 5D, Align Technology, Inc) uses near-infrared imaging technology that assists in detection and monitoring of interproximal caries above the gingiva in real-time.³ Another intraoral scanner (Primescan, Dentsply Sirona) uses a proprietary pixel sensor and dynamic depth scan technology that provides exact sharpness up to 20 mm in depth.⁴

Even with such advanced features at work, however, the dentist remains part of the equation. Thus, to obtain clear and accurate digital impressions, it is essential that dentists perform all of the preparation steps required of traditional impression methods. Good tissue retraction management and a clean, dry field free from liquid and other interferences are necessary for a digital scan to capture the information required for fabrication. The digital scanner is not a magic wand. Just as with conventional impressions, digital scanners cannot see through things that stand between them and the teeth, and therefore they simply cannot remedy the shortcomings of poor preparation.

What's to Come

With all of that said, the future of impression technology appears to be tremendously positive, and a time may well come when dentists can skip the preparation process and still obtain great images. While current scanners rely on optical technology based on light and reflection, future developments in the scanning process likely will incorporate tomography, or ultrasound-based imaging technology, that can function even when some sort of interference is in the way.⁵ A scanner that could "see through" soft tissue would reduce or eliminate the need for retraction; one that understood the difference between a drop of saliva and a tooth surface would essentially eliminate the need for a perfectly clean and dry field.

Other anticipated advancements in digital scanning technology may include additional built-in tools and feedback from the scanner that the dentist can use to aid in treatment decisions. For example, just as today's scanners can provide treatment simulations and restorations, future models may be able to take that a step further through the use of artificial intelligence (AI) technology. With AI, scanners could provide not only clear images and immediate feedback, but also automated recommendations and warnings on everything from how to prepare the tooth to what material to use for the restoration.⁶

Such advancements would change the practice of dentistry. The earlier in the treatment process these parameters are provided and determined, the less likely it is that remakes or backtracking will be required to achieve the right results. Receiving this kind of input from the intraoral scanner during what is basically the first phase of treatment would benefit the practice workflow in ways that cannot yet be predicted.

Then and Now

CAD/CAM in-office dental systems are approximately the same age as digital impressions, with the first system available for use in dental practice, CEREC^®, released in 1986.¹ However, due partly to the need for larger investments of time and money when compared to digital scanners, in-office systems are only now truly becoming widespread among practices.

The use of CAD/CAM in-office systems, which give dentists the ability to scan, design, mill, and deliver restorations in-office (often in a single appointment), has accelerated with the onset of COVID-19. As of 2019, 53% of dentists in a pre-COVID-19 survey spent more than 10% of their yearly practice budget on purchasing new digital technology, such as in-office design and milling systems, and every person surveyed anticipated that percent to rise.⁷ With the unexpected arrival of the pandemic in 2020, that number soared past expectations.⁸ The sudden growth may be because dentists have discovered that many of the new challenges facing the industry due to COVID-19, such as providing patients peace of mind regarding safety, decreasing contamination risk in the practice, and needing to increase profit and workflow efficiency, can be more readily met using digital in-office systems.

Best Practices

To achieve a successful final restoration with a CAD/CAM system, dentists need to follow a number of best practices. As with digital impressions, preparation is key for same-day restorations. Along with the proper handling of soft tissue and isolation of the area for a clean scan, some essential steps are necessary for the dentist to master; perhaps the most prominent of these revolves around the design software and the process required to use it successfully.

Regardless of the particular system and software being used, crown design software requires input from the dentist when it comes to the setting of margins. Systems such as the glidewell.io^™ In-Office Solution are aimed at simplifying the process of margin design as much as possible. In the proprietary software of the glidewell.io system, algorithms are programmed to "seek out" margins by assessing the digital scan of the dentition and looking for the hard edges where retracted soft tissue meets the tooth itself. The software then guides the placement of the margins for the user by creating a preliminary marking around the area where these edges are detected.⁹

It's worth noting that dentists who have previously relied on the dental laboratory to fabricate restorations based on submitted impressions may experience a wake-up call when it comes time to design and mill in-office versions. They may not realize the great deal of time labs often spend compensating for missing information in digital scans and using educated guesswork to fill in the data required to create the crown. Dentists who may be unaware of the amount of post-editing that takes place will likely need to retrain themselves on properly preparing teeth for scanning.

It is also worth noting, however, that dentists who need help implementing CAD/CAM dentistry will typically find that help easy to access. Most CAD/CAM systems on the market offer users training and support to learn not only how to use the new equipment but also best practices to help ensure optimal results. Some manufacturers of in-office systems for CAD/CAM restorations offer remote training courses and customized remote training on their products. Users may be able to connect with training specialists directly to ask questions and learn best practices, and even share their application via an online classroom.¹⁰ With some systems, the user can get started with the help of a specialized training team that might visit the practice on the day the system equipment is delivered and installed. The trainers can provide hands-on, in-person training and instruction for the whole dental practice team and also assist in establishing any new workflows required. Of course, manufacturers typically offer various ongoing skills courses and educational videos.

What's to Come

The future of CAD/CAM systems is already partly upon the dental profession, and it's spelled "AI." The use of artificial intelligence technology in crown design software is well underway; it contributes significantly to the software's ability to produce accurate, usable designs with little to no input from the user.¹¹ For example, glidewell.io relies on machine learning and proprietary AI algorithms developed in conjunction with the University of California at Berkeley.¹² This sophisticated technology uses the vast library of cases at the manufacturer's laboratories as source material when creating customized, unique proposals specific to the case at hand. Similarly, but with some key differences, CEREC^® Software 5 from Dentsply Sirona uses AI to optimally calculate the model axis and preparation margins to provide suggestions to the user that can then be edited as needed.¹³

The acceleration of the field of digital dentistry is constantly bringing better methods and tools into the dental practice. As dentists adapt to these new technologies, it becomes evident how beneficial they can be in meeting the challenges of today's industry, from helping to provide patients with peace of mind to reducing COVID-19 risk and making the practice more efficient and cost-effective.

Justin Chi, DDS, CDT
Director of Clinical Technologies, Glidewell Dental; Private Practice, Irvine, California