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Inside Dentistry
October 2020
Volume 16, Issue 10

CAD/CAM Dentistry Continues to Progress

Q&A With Andrew C. Johnson, DDS, MDS, CDT

Inside Dentistry interviews Andrew C. Johnson, DDS, MDS, CDT, a surgical prosthodontist in Rogers, Arkansas, and an adjunct clinical professor of advanced prosthodontics at the University of Tennessee Health Science Center in Memphis, Tennessee

Inside Dentistry (ID): What are some of the more exciting developments in intraoral scanning that could potentially lead to more widespread adoption?

Andrew C. Johnson, DDS, MDS, CDT (AJ): Anything that provides more purpose or repurpose for these devices is significant. We are seeing the advancements in coloration start to catch up and equal the quality provided by intraoral cameras. Those extra pieces of equipment will no longer be necessary when we can capture 3D images that are just as accurate and realistic. Lip retractors and mirrors for occlusal photographs and retracted intraoral photographs could soon be completely replaced by 3D imaging with full colorization, and the rendered images will be just as diagnostic as any kind of photography.

Many scanners now offer software interfaces that can export multiple different scans as pre-aligned objects, including preparation designs, healing abutments, scan bodies, temporary crowns, and more, so they can be superimposed in the planning software quickly and easily. The accuracy of intraoral scanners is also ever-
advancing, and it may soon match that of desktop scanners, which would allow intraoral scanners to be used with 100% fidelity for full-arch implant restorations and other applications that require extreme precision. Ease of use and cost are some of the other barriers to adoption, but today's intraoral scanners are extraordinarily user-friendly. In addition, some interesting models are being introduced that are more subscription-based or laboratory-relationship-based, which is reducing the cost of entry.

ID: What are some of the developments that you and other dentists would still like to see in intraoral scanning?

AJ: Of course, we want the scanners to be accurate enough not just for placing crowns and individual implant units, but for full-arch restorations. Everyone also wants them to be faster and easier to use, especially in terms of being easy enough to delegate their use to others in the office. I also would like to see larger fields of view, ideally without requiring a larger scanner tip, so that we can capture more information faster. That could potentially allow us to start leveraging these devices more as extraoral scanners for faces, smile frames, dentures, models, and everything else that we scan outside the mouth.

ID: What impact have advances in CAD/CAM software, whether for chairside or laboratory applications, had on practices?

AJ: The speed of treatments can increase when we don't have to spend so much time doing local laboratory work. Instead of putting the case in a box and shipping it, we just email the files. Now, we have digital models that are already preconstructed on the computer screen straight out of the scanner. The accuracy of the treatment rendered is also increasing, particularly with the ability to pre-align all of the digital files; 3D virtual objects can be superimposed in ways that physical models cannot, regardless of how skilled the dentist is at cross-mounting casts on an articulator. Treatment quality will rise because of this. It may not happen immediately-new solutions come with new problems, such as data errors that are not the same as bubbles on a model-but it will rise.

We can enlarge these files on a 27-inch monitor and really evaluate the preparations in ways that were impossible when looking through loupes at inverted tooth preparations in an impression. With the enlarged scan visible to the entire team, the dentist will often be more critical of his or her own work before the patient walks out the door. For example, I may identify the need to adjust a preparation finish line while the patient is still in the chair, whereas otherwise, I might not have caught it until it went to the laboratory. Ultimately, the opportunity to execute all treatment planning at the beginning of these big cases-all in 3D, pre-aligned, accurate, and prototypable in printed plastic-is a huge advantage.

ID: For chairside CAD, what types of applications are the most clinician-friendly, and which ones are still best left to laboratories?

AJ: For single units and small-scale quadrant restorative work, chairside scanning and chairside fabrication can make sense if you are reasonably efficient. For more large-scale restorative work, such as full-mouth reconstructive treatments, significant amounts of time are required to push that kind of production workflow volume through an in-office mill or printer, regardless of the dentist's skill level. It is best to outsource those larger-format cases to dental laboratories with larger-format machines that have the ability to tolerate the cost and complexity that these cases demand.

For applications such as surgical guides, a standard one-piece guide can be printed locally, but a stackable surgical guide system typically should be outsourced because it requires so much time to produce. Regarding removable prosthetics, immediate dentures are easy to print locally, but a final denture is usually better outsourced because of the demands in terms of the structural integrity of the material and the fine esthetic finish work.

ID: When we talk about milling, whether chairside or with a laboratory partner, what are some of the most significant developments in materials that you have seen?

AJ: These materials are becoming increasingly less technique sensitive. Zirconia materials are getting easier to use as the sintering times are reduced and the potential for fracture and catastrophic failures is better managed. These restorations can be fabricated more efficiently and in a more esthetic manner with simplified staining systems. Furthermore, full-contour, higher translucency zirconia materials are making it easier for us to keep it simple while also making it beautiful. Blended approaches are also providing new options, including the incorporation of 3D printed alloys that are baked into polymer blocks for CNC processing or even alloys that are partially 3D printed and then milled to optimize the geometries, the accuracy, and the necessary final finished surfaces for applications such as implant interfaces.

The polymer sciences are always advancing and providing new options in terms of esthetics, strength, and bondability. The next wave will be printable ceramics. In the next 5 years, we will see significant developments and progress as that becomes something that can be considered a mainstream treatment approach.

ID: What other factors are contributing to the improvement of CAD/CAM processes?

AJ: On an equal level of importance with all of these individual machines and materials, if not potentially greater, is the consolidated funnel to which all of these data sets are eventually sent. Certain more tech-savvy dentists prefer to handle it themselves, but a larger portion of the profession does not necessarily want to spend the time learning all of these processes. The greater part of this wave of the future will involve where dentists send the data. It will create a push for local dentists to learn to be data acquisition specialists, so they can basically wield the best-in-class technology and then send the information to a third party that can send back either physical devices or data for the dentist to produce those physical devices locally. Be on the lookout for services that are popping up to help virtually manage data and cases in whatever ways are best for each dentist and practice.

Andrew C. Johnson, DDS, MDS, CDT
American College of Prosthodontists

American Academy of Restorative Dentistry

Surgical Prosthodontist
Rogers, Arkansas

Adjunct Clinical Professor
Advanced Prosthodontics Program
University of Tennessee
Health Science Center
College of Dentistry
Memphis, Tennessee

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