The Shape of Things to Come

02 Oct 2016 Paul Feuerstein, DMD
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Another term we are seeing is 3-D printing. This technology is improving rapidly, and it has expanded into the medical profession, as we have seen with artificial body parts. So far in dentistry, there are no FDA-approved materials for our final restorations, with one minor exception—metal.

Figure 1. Roland’s DWX-4W.
Figure 2. Formlabs’ Form2 printer.

By now, we are familiar with the term one-visit dentistry. Dentsply Sirona and Planmeca have promoted this concept for years, with the former focusing directly on consumers. One of the term’s core components is the existence of in-office design software and a milling unit that can create in-office crowns and small bridges. This technology also allows for fabrication of small appliances such as surgical guides using what is called in CAD/CAM as “subtractive” creation. In other words, a block of material is milled with burs—or in the future, with lasers (dentalwings.com)—to create restorations or appliances. New milling units have entered the marketplace, and they’ll be detailed in a future column. Glidewell introduced the TS150, and Roland (rolanddga.com) has 2 low-cost mills: DWX-4 and DWX-4W (Figure 1), coming in at $18,000 and $25,000 respectively.

As we have seen in the explosion of new materials currently being milled, they have become much stronger, and now some systems can create in-office zirconia restorations. Note that when we tell patients we are making metal-free restorations, zirconia could be perceived as being a metal. Zirconium is a chemical element with atomic No. 40 in the periodic chart of elements. Its symbol is Zr. It is a hard metal, resistant to corrosion and similar to steel. The material we use is ZrO2–zirconium oxide. According to experts, “zirconium and zirconia are distinctly different in terms of crystal structure, stability, reactivity, density, hardness, strength, toughness, etc. Every ceramic has a crystal structure containing both metallic and nonmetallic atoms, but the combination is never referred to as—nor does it behave like—a metal.” I know, I am indeed splitting hairs, but be careful what you tell your patients.

Another term we are seeing is 3-D printing, or “additive” fabrication. This technology is improving rapidly, and it has expanded into the medical profession, as we have seen with artificial body parts. So far in dentistry, there are no FDA-approved materials for our final restorations, with one minor exception (metal), detailed later in this column. So as of right now, to create a final restoration in the office, we still have to resort to the mills.

3-D printers are appearing everywhere, and the cost is plummeting. Dental labs have been using units from Stratasys, Envisiontec, 3D Systems, and others for a long time. Some of these units are fairly large and quite expensive. They originally were used to print models from digital scans, saving orthodontists volumes of storage space, and they are now used to print just about anything we can make out of acrylic. The resolution is in microns, and the fit is excellent. Temporary crowns can be printed, but at least right now, if we are not premaking the temps, the process takes too long. Adjusting your workflow could make it work, although if an office is invested in scanning technology, it might be better off investing in the milling concept, where no temporary is necessary. It should be noted that if a patient needs an appliance such as a night guard, orthodontic appliance, or partial denture, the cases that come from a full-arch digital scan fit better. This is due to the fact that the appliances can be printed, or in more situations right now, the models are printed, and the appliances made on these. Think about printed hard-acrylic models versus those of plaster. As the appliance is being fabricated, small bits of plaster are removed, not to mention the inaccuracies of plaster, especially if it’s not mixed by measuring the water and powder according to specifications. Also, a digital scan is much more accurate in the area of the papilla and interproximal areas, where a full-arch impression, even VPS, “melts” into those areas. This has been well demonstrated by Align Technologies when creating aligners from digital impressions. They fit better at the gingival areas.

Will we see in-office printers? Somerville, Mass-based Formlabs (formlabs.com) has introduced the Form2 printer at the remarkable cost of $3,500. This a robust unit, and Formlabs now has “Dental SG Resin,” which has been approved as biocompatible and can be used to create surgical guides. Its standard resin can be used for models, retainers, and more.

Argen Corp (argen.com) is currently using “Concept Lasers for 3-D metal printing of high noble, noble, and nonprecious alloys. Utilizing 3-D metal printing—also known as metal additive manufacturing—Argen manufactures its portfolio of digitally fabricated dental restorations from single-unit to long-span bridges with LaserCUSING, which builds these products layer by layer directly from 3-D CAD data. The metal powder is melted entirely to provide a fully dense, homogenous structure. The end result is high-detail resolution and exceptional surface finish.” Other possibilities are printing precise wax patterns that can be cast traditionally. Using software, a technician can scan a model or impression and quickly create the wax patterns on the computer screen, setting up several cases at a time and then sending them to the wax printer.

This is just a simple introduction to get you thinking. As the year progresses, I will highlight a number of new products and processes in this exciting area of dentistry.

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