Written by R. David Sager, DMD, Bernard E. Keough, DMD, and Howard B. Kay, DDS Monday, 18 March 2013 09:00
CONFRONTING A MORAL AND PROFESSIONAL DILEMMA
The dental profession is facing a moral and professional dilemma regarding prosthetic dentistry. If dental crowns and bridges (C&Bs) are to be considered the equivalent of medical devices, at least in terms of possible federal taxation, should we not have standards by which these devices can be judged? In light of this new consideration, isn’t it time for the profession to take a hard look at these restorations, their materials, and their making? In recent years, our profession has been chided to base our clinical decisions on “evidence-based” criteria. But what do we really know about the many modern C&B materials and their fabrication systems? By what metric are we to evaluate one against the other and, without reliable long-term clinical and standardized testing data requirements, how are we to arrive at evidence-based decisions and performance expectations? What are dentists now to tell patients about the composition and consistency of their dental “medical devices”? Shouldn’t dentists ultimately know the properties, limitations, and likely longevity of these devices, aka C&B? Is the statement, “It’s the hottest new material on the market!” the message dentists really want to convey? Or, should the dental profession represent, “The long-term data supports the efficacy and reliability of the devices that are being provided”? In our opinion, it’s time to face head-on the moral and professional dilemma that is challenging dentistry today: It is time for the dental profession to establish product standards upon which evidence-based decisions about C&B materials and associated systems are to be made in this “brave new world of digital dentistry.”
MARKETING TRUMPS EVIDENCE-BASED INFORMATION
Dental students prior to the last 15 to 20 years were required to know the specifics of dental materials and prosthetic fabrication methods, and in fact were required to show proficiency by personally fabricating units they delivered in school, as well as those done on board exams, in order to receive a license to practice dentistry. However, changes in education, dental materials, and manufacturing systems have left recent graduates, as well as experienced practicing dentists, dependent upon others for guidance regarding choices in restorations. Increasingly, the “dental industrial complex” has become the sole source of that information, yet all too frequently purveyor knowledge of data on materials and their production has taken a backseat to marketing. As a result, evidence-based dentistry is becoming more and more elusive.
In our opinion, a perfect storm is brewing. The margins of C&Bs are increasingly creeping subgingivally to mate with companion implanted medical devices, or to salvage aging dentitions, or boost youthful smiles, while an understanding of these materials is diminishing. How is the practicing dentist to determine the efficacy, safety, and useful life of today’s new C&B materials/systems? In recent years, we have witnessed C&B materials and their associated systems come and go like the flavor of the month. Is one really better than the other? In the past, product cycles lasted for a generation of dentists...then half of a generation, and today...maybe only a few short years.
A DRAMATIC SHIFT AWAY FROM PFMS: A WISE MOVE?
Weren’t we just hearing how there was a resistance in the marketplace to all-ceramic crowns? Weren’t venerable PFM restorations representing 75% of all US C&B units? And, while the “rebel” 25% all-ceramic C&B producers divided into warring camps of different ceramic materials and systems, didn’t we just witness upwards of 10% a year of all US C&Bs going offshore because of cheap labor—with PFM production of totally uncertain material—in each of the last 4 years? How then are we to greet the recent announcement that a major US dental lab/opinion leader “experienced” a total reversal in production numbers to monolithic zirconia restorations from PFM, in a very short time span, with no scientific long-term data whatsoever driving this reversal? Was their marketing that strong? Is the profession just worn out with so many “options” it is now just opting for the promise of“PFM-like performance” (or better) from monolithic zirconia?
What are we to make of a pioneer purveyor of an all-ceramic C&B system that this past year suddenly spun off its all-ceramic industry benchmark and started globally merchandising “polyplastic” teeth? Didn’t the orthopedic medical profession just complete a decade of “revisions” to eradicate polyplastic implantable hip and knee medical devices?
And what is “all-ceramic” anyway? Feldspar? Leucite? Silica? Zirconia? Lithium disilicate? Or even blends of several materials? Shouldn’t concerns about the cytotoxicity of one of the long-imported, all-ceramic C&B materials/systems be taken seriously and the company not be allowed to relegate this issue to the fine print of company materials, or be allowed to downplay it as being no worse than other cytotoxic materials that have already been used for years? Wait! What materials and what cytotoxic reactions? When did anyone ever mention this in school or continuing dental education? Are we still using these materials? Is cytotoxicity part of an acceptable standard for our materials? Is it acceptable for dental implants?
THE NEED TO REESTABLISH AND CONSTANTLY REVISE STANDARDS
Maybe the flavor of the month/year and lots of options typically acceptable in other consumer markets is not the best and safest way to go when it comes to dental devices. Maybe they shouldn’t be compromised in an effort to continue traditional sales and marketing of “bundled” dental equipment and materials.
Consider the production of zirconia C&B units. Whether it is cores or full contour C&B, the vast majority of zirconia units are made by a 2-stage process of milling an oversized unit from a soft partially-sintered zirconia block. The units are then heated (sintered) again and shrunk to an algorithmically “guestimated” size. It is noted that the raw zirconia varies in composition from block to block, within each block, and from manufacturer to manufacturer. The blocks contain random voids and inclusion impurities (ie, colored zirconia purposefully contains metal oxides), and they result in an anisotropic product (3-dimensionally nonidentical) because of the 2-stage process. As a consequence, the resulting zirconia product is not certifiable by any measure of material consistency, dimensional tolerance, or lot number at the end of fabrication. The fact that shrinkage is nonlinear makes the mathematics of the system “messy” and each unit a unique collection of circumstances. Is it any wonder then why dentists have experienced fit problems of multiunits, or variable/loose fit on individual units? What is the value of a marketing claim of favorable fracture resistance when there is no consistency by lot, and individual testing would necessarily destroy the individual unit? Where is the device accountability for patients in this method of manufacture? By what standard is each unit to be judged?
Dentistry needs to accept the fact that standards must be reestablished and constantly revised. Don’t the public and industry already struggle with failures of acknowledged medical device manufacturing processes with outdated standards? How long will it be before the legal profession gets wind of the state-of-the-art and science in contemporary dental devices?
Questions about quality and consistency of typical zirconia production are especially poignant in consideration of the fact that isotropic (3-dimensionally identical) hot isostatic pressed (HIP’d) zirconia was introduced in dentistry 20 years ago in Europe, at the beginning of the all-ceramic CAD/CAM C&B movement, and has remained the gold standard of zirconia with 20 years of evidence-based research and experience in orthopedics and dentistry. Why have US dental educational institutions, dental laboratories, and the dental profession as a whole disregarded the fact that crowns/crown cores made from isotropic HIP’d zirconia are the gold standard? Modern HIP’d zirconia has the strength to meet the highest human biting force, and with the right combination of today’s technologies, can now be machined in less than an hour, at no greater cost than any other core or monolithic crown. One might ask, with these 20 years of experience, why isn’t there a rush to this unique natural material that is 3-dimensional certifiable in content and consistency from the mine to the mouth? Could it be that the dental profession has been blind to the dental industrial complex’s heavy investment in early soft system manufacturing before the advent of modern hard system manufacturing technology? Whether making a monolithic or aesthetic bilayered dental device, maybe some standards would be in order.
IT IS TIME TO QUESTION
In this brave new world of digital dentistry, we must question how we are applying CAD/CAM technology to the making of C&B devices. At the end of the day, if it is still just an artisan process where technicians must manipulate both computers and hand instruments to make units fit well, with no real improvement in quality or productivity to justify the cost of that technology, where is the advancement in dentistry? Is it possible that the “dental industrial complex” promoted new materials and technology in this last decade with an eye more on their bottom line than on gold standards? Is it possible that companies promoted their systems without regard to assessing where new technology would best benefit a value chain in a manufacturing process? When will dentists and dental lab owners finally tire of banishing yet another piece of equipment to the store room for reasons of “systems upgrade incompatibility”? The half-life of technology is exponentially decreasing at a time where expectation of longevity of medical devices is increasing. Could it be that medical device categorization and federal taxation will spawn greater inspection of the value chain and become an impetus for re-establishing standards? Maybe it is time for the dental and laboratory professions to tire of unsustainable consumer-grade table-top equipment and move toward modern manufacturing solutions.
As the number of dental technicians in the US dwindles, maybe it is time for motivated master technicians to migrate back to chairside for the best initial case input and design, and to personalize output from centralized custom automated mass manufacturing platforms that are able to realize the standards of quality and consistency of the semiconductor industry. Maybe in the future, dental technicians will reside in the “clouds” of application rather than being fabricators. With regard to materials and systems, maybe less really is more in the brave new world of digital dentistry. Maybe it is time for dental devices to have real standards, allowing true evidence-based decisions to be made for our patients.
Dr. Sager, after graduating from Washington University School of Dental Medicine, completed a hospital general dentistry residency at Illinois Masonic Medical Center, Chicago. He is the past president of the Academy of Dentistry for the Handicapped, cofederating president of the Federation of Special Care Organizations in Dentistry, and the chairman of the nonprofit Midwestern Institute for Advanced Dental Studies, Inc. He is widely published, has lectured internationally, and served as CEO of AltaTech Biotechnologies, NA to obtain FDA clearance to introduce the Camlog Implant System in the United States. He is active in multiple dental, civic, and charitable organizations, and he maintains a general and hospital dentistry practice in Manhattan, Kansas. He can be reached via e-mail at
Disclosure: The authors report no disclosures.
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