Additive Manufacturing Strategies

Not All DLP Machines for the Dental Industry Are Created Equal

ST Medical Devices

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Zahn Dental’s Beth Collington will be speaking at 3DPrint.com’s upcoming AMS online industry summit (Feb 9-10, 2021). Register here.

It is critical in today’s evolving marketplace that utilizing your business’s capital for technology is money well spent.  The percentage of your budget that is allocated on a capital purchase needs careful consideration on how the technology purchase will best fit into your overall long-term planning process for the business.  Consideration on how to implement a growth factor and return on your investment per department should be factored into the technology selection.  Additive manufacturing consistently proves a quick and strong return for the dental industry. The question then becomes how a Dental Laboratory or Clinical practice can best choose a printer that delivers productivity and consistency over time for your lab.  In 2008 there was one DLP company that was focused on implementing 3D printing into the Dental Laboratory market.  In 2019, there were over 170 manufacturers globally who sold DLP printers primarily focused on the Dental market segment.  With such an influx of printers in the market, this article should guide a lab owner who is considering a 3D printer on what to look for and what is needed for next generation chemistry for resins in 3D printers for Dental applications.

The hardware and functionality can make a huge difference with all DLP printers.  First consider the projection. There is always a projector that is based on the TI DLP chipset. There is also an LED light source that powers the projector and ultimately delivers the light to cure the resins selected. This combined with the technology used to create the layer and whether the layer is glued to the bottom of the material tray or floating above the bottom of the material tray are all elements that can enhance or detract from the accuracy of your final restorations. In addition to the technical requirements, there is also the selection of the materials available for the printer from the manufacturer.  The ability to deliver many indications and vast array of material availability along with the machine’s capability to process these materials should be a key factor in your investment.

As a rule, it is preferable to purchase a printer with the highest “Native” pixel count projector. For example, there are many projectors that are running the 1920 x 1080 Native pixel resolution while the newer ones are running either at 2715 x 1528 or 2560 x 1600 Native pixel resolution.

It must be clear that the higher the resolution of the projector the smoother the surface finish is (or less pixelation ) this is known as wood grain effect. Many 3D printer manufacturers try to focus on pixel smoothing or pixel tuning but the key starting point in a high-quality 3D printer is to identify the real native resolution of the projector.

The next point to consider when purchasing a 3D printer is if the projector is running at an LED light source of 385 nm or 405 nm wavelength. Some less expensive projectors typically use lower cost DLP chipsets which are powered by a 405 nm LED light source. More expensive professional- grade projectors use a 385 nm LED light source that works only with Industrial DLP chips designed to work at the lower wavelength.  So, we need to ask then “Why is 385nm preferred in Dental 3D Printing?”

Most chemistry converts from liquid to a solid using an “initiator” which initiates the chemical reaction with the use of light. The initiator is most efficient at 385 nm compared to 405nm, thereby delivering the highest degree of conversion of the liquid to a plastic. This is very important in dentistry because you need to have enough energy to deliver the highest degree of cross-linkage when delivering permanent end- use restorations. In addition, it is very important to use high power LED so as to dump a lot of power at each individual layer to fully convert the liquid into a solid layer that is fully “plasticized and cured” and stable over time. The ability to deliver end- use restorations require high power LED, so it is important that you can deliver power that is higher than 5 mw/cm2.

Consider that there are two ways of layer curing that happens in the DLP printers. One is the traditional DLP printing originally launched by EnvisionTEC in 2003, where the layer is formed at the bottom of the tray and then peeled away before the next layer is formed. The second method is where the layer is floating and not glued to the bottom of the material tray and is known by EnvisionTEC as Continuous Digital Light Manufacturing or cDLM technology, and by Carbon as Continuous Liquid Interface Production™ or CLIP™ technology.

This variation between standard DLP curing with other printers in the market occurs where the layers are glued to the bottom of the tray and are peeled away reducing the strength in Z to  ½ the strength in X and Y. When using a non-peeling technology such as EnvisionTEC cDLM and Carbon CLIP technology, then the strength in X, Y, and Z is the same. These parts are known as ISOTROPIC. The ISOTROPIC property is extremely important in digital dentistry as there is always a lot of load when chewing from the jaw and strength being the same in Z as X and Y becomes paramount.

Finally, in order to deliver end- use restorations or finished dentures and clear aligners that are directly printed, it is important to be aligned with a 3D printer company that can deliver in these categories.  Material performance that gives you more versatility along with the clear understanding the manufacturer of the printer will support the performance of the material in the printer. More critical is they stand behind the material’s performance when the restoration is printed, whether fixed or removable. Choose a printer where the company has a strong infrastructure of service and is supported by technical services to deliver on-time support when needed.

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