Build Me Up Buttercup

Paul Feuerstein, DMD
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…a 3-D printer looks at the software design as if it was a CT scan with thousands of layers….[It] stacks…slices on top of each other and…“welds” them into the end product.

For years, we have been watching restorations being created before our eyes in desktop mills. CEREC (Dentsply Sirona) and PlanMill (Planmeca) were, of course, the first and continue to dazzle us and our patients with new and more complex restorations. Looking at the actual process, software is used to design a restoration, and it creates a file that is sent to the mill. Next, you have to decide which material you want to use for this restoration and put an ingot (block) in the machine before you press “mill.” There is also some artwork involved if the blocks have multiple colors. The designer can virtually place the upcoming restoration in the block to determine which part of the tooth gets which shade.

Once this is done and the button is pushed, the mill uses one or more burs to “drill” out the restoration. This is called subtractive manufacturing, as the burs are removing material from the block. I went through this exercise to begin a discussion of additive manufacturing of restorations, or 3-D printing. With the proliferation of these new printers in the marketplace, it would seem that all one has to do is go through the same design process, push a button, and print the restoration. Well, not quite yet for crowns and bridges. First, here’s a primer on the process.

To simplify 3-D printing, I like to make an analogy to our old copy machines that used toner. When a letter was printed, a black powder was sprinkled on the paper and heat fused it to the page. Imagine if you kept putting the same piece of paper back in the bin and reprinted the exact same thing hundreds of times. The toner would build up on the paper, and soon you would have raised letters. This is similar in concept to a 3-D printer. In general, a 3-D printer looks at the software design as if it was a CT scan with thousands of layers. Just as we can create 3-D reconstructions of our cone-beam images, the printer stacks these slices on top of each other and essentially “welds” them into the end product. Here is where some of the confusion comes in: We are going to start hearing about a variety of methods of printing, and it will be reminiscent of the introduction of digital x-ray sensors. There were wars about which was better—CMOS or CCD. We heard about line pairs and electrical differences, but, in the end, what really mattered was the diagnostic quality of the end product (the image). There is a lot of talk around 3-D printing about resolution in microns, speed of printing, size of the print plate, how many things can be printed at once, and more. Then come the discussions with new acronyms, like “SLA,” “DLP,” “FDM,” “SLS,” “SLM,” and more. And once you think you are an expert on the differences between the systems, new enhancements show up as well as new processes. The key is that all of these systems can read a standard file that you have created with a restoration or other design. As I said, at this second, we are not yet printing final crown or bridge restorations (at least at press time), but we are printing other dental products, such as models, mouthguards, surgical guides, retainers, orthodontic bracket guides, dentures, and many more. Two of the companies, EnvisionTEC and NextDent, have begun to manufacture over 40 types of printing resins for almost as many applications in dentistry. New names are appearing that we have never heard of. A few examples are 3D Systems, Formlabs, EnvisionTEC, Stratasys, Asiga, Carbon, and more, which are well known in other industries but have recently come into the dental marketplace. One new company, SprintRay, makes the MoonRay printer, and they are focused exclusively on dental applications. But fear not, more familiar names are coming into the field. VOCO, Planmeca, Kulzer, and other dental companies are all introducing 3-D printers. Keep in mind that a company like VOCO is a materials company, so this is merely an extension of their dental product line. As noted, dentures are one dental restoration that is now being printed. The printing resins come in a variety of shades of pink and have tooth-colored resins that will print the teeth. Right now, these are done in 2 steps and the 2 pieces (the denture base and printed teeth) are fused together.

Many of these units cost less than $20,000, some are less than $10,000, and a few are less than $5,000, thus making them affordable for a dental office. Also, the ROI is amazing: The cost to print most of the appliances, guards, and guides is less than $10. Speed is a minor concern right now, and it would be inefficient (at least now) to print one crown, but, at this cost, it’s not really an issue. There is also some “post-processing” that has to be done with many of the resins. Most have to go through one or more rinses in an alcohol bath, followed by UV curing and drying. This, of course, adds time to the process and requires a couple extra pieces of equipment. Similarly, those of you who mill lithium disilicate or some of the in-office zirconias (except Glidewell’s BruxZir NOW) know that you need an oven and time after the restoration is milled. One of the new desktop 3-D printers, Structo Velox (Structo) (structo3d.com), actually has a robotic system that lifts the printed product, dips it into the cleaning baths, and moves it into the UV curing and drying section. Also, with the proliferation of new orthodontic aligners, there will be software available to allow an office to plan a case and print out all of the models and/or aligners at a fraction of retail cost. Many of my colleagues are posting information about 3-D printing on social media, as well as giving courses, writing books, and more. The trade show booths are now littered with new units. Watch this field closely and often, as you will see a lot of rapid changes—and don’t blink.

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