You must be signed in to read the rest of this article.
Registration on AEGIS Dental Network is free. Sign up today!
Forgot your password? Click Here!
CAD/CAM Restorative Dentistry
Ed Flocken, CDT, BA
CAD/CAM dentistry became available when the visionary, Dr. Werner Mörmann, developed CEREC in the early 1970s. It began when he was searching for better material solutions and ways to quickly and efficiently restore teeth in a predictably manner. At that time, many technicians would argue that it was to eliminate the time and cost of using commercial dental laboratories. I, for one, was a skeptical technician and thought that a machine would never be able to replace the skills of trained technicians. Early restorations lacked good fits (ie, over 100 microns) and were not very esthetic. It was often said that the restoration was “an island of ceramic, surrounded by a sea of composite or cement.” We cannot say this today.
In a short time span of 5 years, the restorations that are being produced chairside, as well as in dental laboratories, can boost marginal integrity averaging 20 to 50 microns. This is because the scanning ability has progressed from 2-D to 3-D, and the software has come a long way from its early beginnings. Milling (CNC) machines have also improved with more axis and stable platforms, producing better results. In addition to better fits and accuracy, there are now myriad new materials that can be selected for different types of cases.
Early CAD/CAM restorations were made from feldspathic ceramics with low flexural strengths. Today, we have materials in the 900-MPa to 1,400-MPa range that are veneered with ceramics that are kind to natural dentition. A relatively new material, lithium disilicate (IPS e.max, Ivoclar Vivadent), is strong and esthetic, without the need for veneering with ceramics. Also, with the price of gold climbing, titanium will become the new noble alloy of choice.
Nearly 50% to 58% of all indirect restorations produced today are, in part or entirely, manufactured by a CAD/CAM system.2 By the year 2015, it is likely that this growth will increase by another 15%.3 It is my belief that many dentists may not know that a CAD/CAM machine may have been involved in the fabrication of the restorations they recently received.
In addition to the single-unit and 3-unit bridge capabilities of CAD/CAM, the development of software now enables the design and production partial frameworks, orthodontic appliances, and custom implant abutments, as well as custom overdenture bar restorations and conventional Dolder and Hader bars. Software development is moving quickly to not only articulate bite registrations, but also to emulate classical jaw movements such as protrusion, retrusion, laterotrusion, mediotrusion, and immediate side shifts. Today’s software parameters can already adjust occlusion by various micron settings and place working cusps into their respective fosses with the “click of a mouse.” It also can design full-contour crowns and automatically adjust contacts and occlusion using existing dentition as a reference.
The best place to see all of the new and exciting developments is at the IDS meeting in Cologne, Germany. Last year there were more than 170 CAD/CAM related companies in attendance, and the new innovations were exciting and amazing. What became apparent at this meeting were the many peripheral systems available that are driven by CAD/CAM technology. Convergence manufacturing is now possible with “open architecture” systems. It also is possible to manufacture with “rapid prototyping” (ie, models, printed patterns in acrylic, wax, and alloys from open STL files). This assures accuracy, higher productivity, material and labor savings, and reduced possibility of remakes. CAD/CAM milled titanium will replace many of the noble and high noble alloys based on biocompatibility, radiolucency, clarity of finished margins, and cost. As Birnbaum noted, digital impressions will replace conventional impression material and techniques and also will eliminate problems associated with conventional impression-taking procedures. Die stones and die materials will be replaced by very accurate printed or milled models, and virtual articulation will eliminate many articulation problems, as well as articulators. CAT scans can and will be combined with virtual scans to help in diagnosis and fabrication.
New technologies are expensive and the learning curves can be steep. Thirty-six percent of CAD/CAM technology is currently manufacturer-driven, and already many of these systems are appearing in progressive dental and dental laboratory schools. Forty-four percent of dentists are educated about CAD/CAM by their laboratories and associates. Dental academies, such as the Academy of CAD/CAM Dentistry (ACCD) meetings, and conventions provide a “first look and see” of this technology and make it easier to understand and use by experienced users. In a down economy, however, there is a concern that many programs, lectures, and courses may be reduced or even eliminated. This will definitely have an impact on the advancement of this technology. As a result, more webinars, TeamViewer sessions, and Skype instruction about CAD/CAM will occur over the Internet.
There is and has been a new paradigm shift within most progressive laboratories. Step-type laboratory personnel are seeking to gain more information technology training and experience in order to protect themselves against losing their conventional role within the laboratory to CAD/CAM fabrication. It has always been difficult to find good, dependable technicians, and even more difficult to train them on the job. Most quit within 3 years to pursue other types of work due to a lack of opportunity to advance, low salaries, and the stress to produce a solid bottom-line profit. The National Association of Dental Laboratories reported that the average dental laboratory technician earns 12.5% to 18% net profit, depending on the size of the laboratory.4 Currently there are 13,000 dental laboratories, half of which are one-man laboratories; there is a total of 53,000 “lab people”.4 There is currently a 1.2% decline in dental laboratories due to decreased revenues.
The cost of remaining in business in a declining market has forced many laboratories to close their doors. This trend also has caused laboratories to seek new and innovative ways and systems to balance the loss of income, the ability to manufacture, and remain cost effective. The most logical solution is CAD/CAM technology. Eventually, the effects on this trend will impact all dental practices, because it will become increasingly difficult to find skilled technicians to work with and understand what is needed to achieve successful restorations.
Databases will not and cannot replace the human factor. It will always be necessary to have a skilled technician or practitioner involved in analyzing data and telling machines what to do. Machines can perform intricate tasks and make proposals based on information but, ultimately, a skilled person is needed to press the “start” button.
1. Culp L. Lecture. New England Academy of Cosmetic Dentistry. October 2007;Boston, MA.
2. Dental Lab Products. Innovation, Excellence, Expertise. 35(4):36.
3. LMT. 26(6):16.
4. Napier B. “State of the Industry.” National Association of Dental Laboratories Lab Congress. 2009; Chicago, IL.