The Ceramic Dynamic
Posted Apr 28, 2011 in Technical
When it comes to porcelain purchasing decisions, "there are so many choices, and so little time," says long-time LMT columnist Bill Mrazek, BS, CDT. Here, Mrazek provides a comprehensive look at the explosion of new materials, their applications and how you can make the best decisions for your business.
There was a time, not too long ago, when a laboratory owner and/or manager would spend most of his or her time actually making teeth or focusing on the normal routine of running the laboratory. Ah, the good ol' days! You don't have to be a 30-year veteran like me to earn the distinction of remembering the "good ol' days;" after all, enormous changes have taken place just during the last five to 10 years, and the speed at which these changes happen continues to accelerate. It's easy to get excited about the technological advances; that's the "technician" in us. But it's also easy to feel overwhelmed by the decisions that have to be made when trying to adapt to these changes, and do so in a relatively short time frame to stay competitive; that's the "business owner/manager" in us.
At LMT Lab Day in Chicago in February, I talked with friends and colleagues from laboratories of all sizes and one of the topics that came up in almost every conversation was how to decide what ceramic technologies to purchase, and how long that technology would be around before it's replaced with something new.
The number of offerings in ceramic-related products is astounding, which is great on one hand because it provides us with choices, but confusing on the other, because it increases the possibility of making the wrong choices for our laboratories. To put it in perspective, there were 207 exhibitors in the LMT Lab Day exhibit hall and one out of every 10 was showcasing a ceramic product or products. Of course, porcelain-fused-to-metal restorations are still the staple for many laboratories, and an abundant number of PFM porcelain systems are available. In today's competitive market, the need to work with materials that minimize labor and create efficiency is more important than ever. Ease of handling, minimal shrinkage and the ability to match the increasing demand for 3-D shades out of the bottle are all important characteristics to consider.
While the porcelain-fused-to-metal restoration is still considered by many to be the esthetic standard for clinical longevity, the improved esthetics and biocompatibility--coupled with soaring precious metal prices--continue to drive the move to metal-free dentistry. The pressed ceramic technique has become one of the most accepted, successful and cost-effective methods of fabricating metal-free restorations. Just about every company that manufactures porcelain veneering powders offers ceramic pellets for pressing. They are generally manufactured using leucite-reinforced chemistry and are available in a variety of shades and opacities for ceramic inlays, onlays, laminate veneers and full coverage anterior restorations; all leucite-reinforced pressed metal-free restorations require bonding. A number of manufacturers also offer leucite-reinforced pellets for the press-to-metal technique.
Lithium disilicate pellets offer greater strength that allows for conventional cementation and the fabrication of three-unit anterior bridges. However, these pellets cannot be used for press-to-metal techniques because of incompatible coefficients of thermal expansion between the lithium disilicate ceramic and the alloy.
The most recent development in pressable technology, the press-to-zirconia technique uses shaded pellets with a coefficient of thermal expansion that is compatible with milled, yttria-stabilized zirconia understructures. The press-to-zirconia pellets are available in opaceous and translucent VITATM classical and 3D shades, depending upon the manufacturer.
With a success rate and long clinical history rivaled only by PFM restorations, alumina copings and understructures are created by three methods: building onto a refractory model then sintering and glass infiltrating; scanning, milling and sintering; and a more recently introduced technology, electrophoresis deposition using an automated die dipping process into alumina slip material or an even stronger alumina/zirconia hybrid slip material. Alumina restorations are usually limited to full-coverage restorations and small bridges.
About 20 years ago, CAD/CAM was relatively new to dental technology. Initially, it was introduced for chairside clinical dentistry, but didn't really have a dramatic or immediate effect on the laboratory...boy, have things changed!
CAD/CAM has not only become the future of dental technology; it is the present and must not be ignored! Just about any ceramic material that exists in dentistry is available in a block form for milling: leucite-reinforced ceramic, lithium disilicate, alumina, zirconia (glass infiltrated and yttria stabilized) and even composite. The leucite-reinforced blocks are preshaded and are also available with gradiated shade and translucency levels within the block so they can be milled to full contour without the need for layering. Lithium disilicate, alumina and zirconia are meant to be used for understructures because of their monochromatic opacity.
Of course, selecting the right veneering material for each type of understructure--whether it's metal or ceramic--is critical because the materials must have compatible coefficients of thermal expansion. Layering and firing porcelain powders that aren't compatible with the understructure's coefficient produce results that will make your heart stop: everything looks pretty good after firing until the restoration approaches room temperature. At that point you realize you've made a terrible mistake and it's remake time. This is especially devastating when the understructure is ceramic. While a metal coping or framework can be salvaged by stripping and re-applying the porcelain, this is generally not the case with a ceramic understructure.
Another consideration when evaluating our choices is the increasing number of combination cases. Dentists are taking advantage of the variety of restorations laboratories are offering in order to conserve tooth structure, improve esthetics and ensure biocompatibility. Therefore, we're seeing more combination cases where, for example, a laminate veneer may be prepped next to a zirconia crown, which is next to a four-unit PFM posterior bridge.
But because these new technologies and related materials were not developed at the same time by the same manufacturers, it's very common for a laboratory to have a PFM system from one manufacturer, pressable ceramic materials from a different manufacturer, and alumina and/or zirconia veneering powders from other manufacturers. Due to different manufacturing, pigmenting techniques and philosophies, it is very likely that a combination case fabricated with veneering materials from three different companies may not match when seated in the patient's mouth.
If you're in the process of expanding your offerings or just want to minimize the variables between different manufacturer systems, consider materials that are manufactured by the same company, especially porcelain veneering powders. This ensures that there is a much greater chance of all types of restorations matching in the mouth because the same manufacturing and pigmenting principles have been applied to each system.
Finally, making purchasing decisions requires careful planning that is not limited to just a specific system or material. Laboratory owners also need to take into account several other factors, including:
- Training, gradually transitioning new techniques into the lab and how technicians' responsibilities will change;
- The laboratory's potential marketshare for new types of restorations and whether or not the technology will bring in new business or simply replace existing business;
- The return on investment--especially on the more expensive systems--and whether the equipment will still be viable as new technologies are introduced, or if outsourcing is a better financial decision for your business.
Most importantly, what will happen if you do nothing, and simply maintain a wait-and-see attitude?
Decisions, decisions. It's an exciting time in our profession and--given the choices--it can also be a challenging and frustrating time. But proper research and sound decisions can relieve the frustration and increase the excitement.
© 2015 LMT Communications, Inc. · Articles may not be reprinted without the permission of LMT
Nothing has yet been posted here.