CAD/CAM and Digital Dentistry
A personal perspective
David Burt, DDS
The practice of dentistry has changed a great deal in the past 40 years, especially with the advent of CAD/CAM and digital technologies. Duret’s concept of combining optical images with computer numerical control (CNC) industrial milling in the 1970’s followed by the introduction of the first CEREC chairside unit by Dr. Werner Mörmann in 1985 started our profession on a path that has forever changed the way dentists handle their practice workflow.
The first three CEREC platforms were fairly crude in their image acquisition in that the preparation and surrounding teeth had to be powdered with titanium dioxide for the camera to be able to “see” and capture them. The software was challenging as well in that the operator saw only a series of dots representing the basic outline of a given tooth proposal. It was a 2-dimensional representation of a 3-dimensional object, presented from the perspective of the middle of the preparation looking outward. Preparation margins were painstakingly derived by matching up two sets of dots, which was the major complaint of dentists who were fearful of open margins and ultimately the tech itself. In addition, the practitioner had to be able to interpret these “dot drawings” and mentally visualize what the CAD proposal would ultimately look like. Even the contact size and strength of a given proposal was determined by the size of the “parabola” of dots rendered by the software. Utilization of this early CAD software was daunting to many dentists, and they required hours of practice to understand the intricacies of virtual designing and develop confidence in their ability to create a restoration that was a decent representation of a tooth. Additionally, the milling capabilities were equally challenged in that they used a diamond bur and wheel to carve a given design from blocks of either fine grained feldspathic porcelain or newer materials (eg, glass, ceramics), which promised higher strengths and easy polishing. Milling times for the early units ranged from 10 to 20 minutes for a full crown, then the resultant restoration had to be adjusted for fit and occlusion and polished or glazed using an oven. To overcome the problems associated with milled porcelain being inherently too weak to survive in the posterior, the blocks were fabricated to have low porosity and be crack free and milled at room temperature rather than stacked and fired. These restorations also had to be bonded rather than cemented to achieve the 140 to 160 MPa of strength needed for application in the mouth.
A significant step forward in CAD software came in 2003 when CEREC introduced the first true 3D representation of a restoration proposal to the design process. In addition, this enhanced software gave the practitioner the option to allow the computer to derive a design proposal based on a preloaded database of teeth developed by Lee Culp, CDT. Now more doctors could visually grasp the applications and create relatively esthetic restorations with confidence and speed. Along with this advancement came another CAD/CAM system to the dental chairside marketplace: the E4D from Schein. The E4D was touted to be a viable alternative to the dominance that CEREC had enjoyed for a number of years. While it initially seemed to be a wannabe in the CAD market, the E4D’s software proved itself to be as robust as CEREC’s in ease of use and designing capabilities, while remaining different in a few areas. Both CEREC and E4D were now capable of milling a crown in a very short period of time, and the E4D’s advancement of not having to powder all of the preparations was a new twist in the war of the competing CAD/CAM systems. The race for the CAD/CAM market share was heating up.
Fast forwarding to 2011, CEREC showcased the first truly powder-free imaging camera for all applications. It also featured refined design modes that utilized data from a preparation’s neighboring teeth to give the doctor a proposal that was customized to the morphology of the patient’s dentition. Dental CAD had reached the point where labs could now totally design and fabricate a crown or bridge from a scanned impression or a file and virtual model created by a digital camera. Today, a plethora of systems now compete for the digital dental market with options that range from chairside designing and milling to the ability to send digital files to labs that then create model-less restorations, surgical guides, and even dentures using the CAD/CAM process. The digital age is upon us in full force, and my patients who now have 17-year-old chairside restorations, still functioning well in both use and esthetics, couldn’t agree more.
About the Author
David Burt, DDS, maintains a private practice, Mountainville Dental, in Allentown, Pennsylvania.