The Current State of Digital Impression Systems in Dentistry
An overview of digital systems for general practitioners
Chad C. Duplantis, DDS
Successful indirect dentistry depends upon multiple factors. Clinicians often concentrate on preparation design, impression materials, restorative materials, luting selections, and, of course, the cost associated with all of these steps. Each of these factors plays a role in the success or failure of the final restoration and the patient’s overall dental experience. Of all of these factors, the one that patients seem to remember—and complain about—the most is the impression, including everything from the material to the technique and their overall experience of it. What if a clinician could improve that technique to such a degree that it was not only incredibly accurate, but it would also substantially improve the patient’s experience? What if a final restoration or other oral device could be produced that is every bit as accurate as a dental impression?
A Brief History of CAD/CAM Dentistry
CAD/CAM dentistry has been in use in dental practice for almost 30 years. Duret began the digital revolution in 1971.1 However, Mörmann was the first to bring the concept into clinical practice with the CEREC 1 in 1987.2 The original system, which was not very user-friendly, was limited to inlays and onlays. Sirona (www.sironausa.com) developed CEREC and had the market cornered for many years, and was a true pioneer in the industry. CEREC had no competition until several years later, when E4D Technologies’ (www.e4d.com) chairside CAD/CAM system was introduced in 2007.3 Over the past several years, the landscape has become more diverse as other dental manufacturers have introduced their digital products. The choices are so numerous that it can be overwhelming for the dentist when entering this facet of dentistry.
CAD/CAM dentistry has evolved a great deal since the first CEREC was introduced, and it is the changes in the more recent years that have influenced the profession in powerful ways. The concept of CAD/CAM dentistry used to be marketed as scanning, designing, and milling of restorations all in one visit. This concept limited the materials available for the final restoration, and it also virtually eliminated the dental laboratory from the equation. Over the past several years, the mills have become more of an option, and the scanner as the driving force of CAD/CAM dentistry has been re-established. With laboratories becoming more involved again, the material choices available have expanded, as have the dental indications. The systems that are available today are not only capable of producing inlays, onlays, and crowns, they are now capable of producing digital impressions that can be used to fabricate almost any restoration or product that a traditional dental impression can. One of the experts in the field, Dr. Daniel Wismeijer, sums up the new age of digital dentistry with the following profound statement: “Digital dentistryis developing to a world where patients and in mouth products are analog, but everything in between becomes digital.”4
Accuracy of the Current Digital Techniques
The scanners of today demonstrate an incredible level of accuracy. The stereolithography (.STL) models produced from the scans have proven to be an accurate replacement to the traditional plaster models with minimal distortive potential.6 These models are made of a hard resin that are polymerized by ultraviolet light. It is an additive technique that creates an incredibly accurate model based upon the .STL file generated by the scanner used.7 These models do not chip or abrade. They provide the dentist with a model that can be used repeatedly with no distortion.
With regard to the restorations produced,the process has also proven to be incredibly accurate. The anatomy in the restorations was once an issue, but this has improved greatly over the past 30 years. The initial concept required the anatomy to be ground in by a handpiece.1 Occlusal anatomy is no longer an issue, nor is the marginal or internal fit. Recent studies have concluded that the marginal of digitally manufactured crowns is superior to that of conventionally made crowns. The internal fit of digitally produced restorations has been proven to be as good, if not better, than crowns fabricated using conventional techniques.8-10
It is of importance to note the speed at which the digital impression process takes place. In considering the total amount of time to acquire a scanned impression versus a conventional impression, digital impressioning is considerably faster. For certain impressions, digital techniques have been proven to be up to 23 minutes faster.11