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Inside Dental Technology
July 2022
Volume 13, Issue 7

The Boundless Variety of 3D Printing Hardware

Benjamin Taylor

As of 2022, the dental 3D printer market is flourishing, and a growing number of different models are becoming available, making it very difficult for customers to differentiate between one printer and the next printers. The author works with dozens of printers and post-curing units during validation processes, which allows for a unique perspective on the printer market. In order to accurately compare and analyze these 3D printers, it has become necessary to break them down into categories. There are printers on the market that are very affordably priced at $5,000 and well below, while most range between $5,000 and $50,000, and very high-end selections can cost well over $50,000. The challenge is knowing how to assess these printers in the dental space, and then determining what is worth the investment. Most printers can be classified into one of three buckets.

High-Volume 3D Printers for Laboratory Use

High-volume printers from established manufacturers may come at high costs, but if the volume capability of the printer meets the laboratory's high demand, the result can be improved production, large profits, and a quick return on investment. Well-established, high-volume dental laboratories became the early adopters for these high-end printers because they understood the potential increase in workflow efficiency from transitioning to digital 3D manufacturing, resulting in exponential business growth. With high-volume manufacturing and a correspondingly high price point comes an expectation for printer reliability and technical support from the manufacturer. These high-end printers must deliver excellent print speed and precision, high quality, and consistent reliability in order to continue expanding in the dental market.

Desktop/Mid- to High-Cost 3D Printers for Clinical or Laboratory Use

Most dental 3D printers fall into this range, priced at $5,000 to $50,000, and offer different workflow packages and services in an attempt to gain a competitive edge. This is the range where people are most often uncertain about making a purchase. When determining which printer fits a laboratory's needs, several factors must be considered: the applications for which the printer is intended, the volume of printing expected, and what aspects are most important for the laboratory's particular situation (material availability, printer speed/quality, technical support, user interface, workflow compatibility, etc). Each printer has its advantages and disadvantages, and determining what is most important will help drive the eventual decisions. For those who are new to dental 3D printing, material availability and technical support are two very important aspects to keep in mind.

An open-source 3D printer gives users the ability to print with whichever material they choose, while others may restrict choices somewhat but still offer compatibility with multiple validated resins. If considering a closed-system 3D printer, it is important to determine just how restrictive the system may be.

Comprehensive customer support helps to ease new users along the learning curve of 3D printing, and solid technical support is essential when hardware needs to be fixed or replaced. An intuitive user interface and good controls also help with overcoming the learning curve, as well as minimize hiccups in daily operations. Finally, for those who are tech-savvy, there are some mechanical differences across different printers to keep in mind, including vat design and peeling mechanisms, which work to minimize printing peel force, optimize surface quality, and increase resin dynamic flow during printing. The printer companies that succeed in all of these aspects will ultimately thrive.

Desktop/Low-Cost 3D Printers for Clinical Use

Most inexpensive LCD printers and small desktop printers fall into this bucket. This bucket should not be considered "inaccurate" or "bad," but users should keep in mind that you get what you pay for. The quality of these printers meets and sometimes even exceeds the level of printing quality provided by some higher value desktop printers, but there are tradeoffs to consider. Some of these printers can take 20% to 30% longer to print a device. If printing speed is not of concern, then most of these printers provide very high value to low-volume users. Beginners with low volume requests who choose this route will likely learn about 3D printing through experience, since some of these companies do not offer extensive support services, if any at all. Once users become skilled and confident, they can transition into the next category to ramp up their output. It is also worthwhile to consider that inexpensive hardware often leads to frequent upgrades or component fixes, including resin trays, build plates, and LCD screens.

Important Considerations

As mentioned above, there are several aspects and features that need to be considered when investing in digital manufacturing. Choices must be made not only about the type of printer , but also about preferred material, as well as compatible washing and curing units, which make up the digital ecosystem. All these things must be considered in regard to the others.

3D Printers

3D printer companies and enthusiastic end users have been seen trying to push the limits of 3D printing. Controlling the dynamic flow of 3D resin during the printing process has become the focus in recent months as users and companies have found ways to increase surface quality and decrease overall printing speed by making simple modifications to the build plate. Perforations, while not optimal in the author's opinion, have been tested to help minimize dynamic resin flow during the print (resin is able to flow through the build plate instead of around), which in return decreases the amount of peel force of the print and wait time needed for the resin to flow back under the build plate after every layer. Other companies have also been testing smaller build plates, which are more efficient as it ultimately lowers the buoyant force of the displaced build plate and achieves the same goals stated above in making 3D prints faster while maintaining high quality.The speed of the overall print is ultimately determined by exposure time per layer and height, but it is heavily influenced by the layer height and the time between layers (mechanical lift, wait, retract, etc).

Print resolution must be examined in two very different ways: X-Y resolution and Z resolution. X-Y resolution is most important when comparing overall print resolution between one printer to another. X-Y print resolution in DLP 3D printers is the pixel size in the projector. The smaller the pixel size, the more detailed and accurate the result. Think of a DLP projector as a chessboard, and you can only create images by filling in the chessboard squares. The more squares in the matrix, the more detail you can have in the image. The bigger the pixels, the more you will see staircase-like detail. Layer height and X-Y resolution, combined with proper printer parameters, can also determine the surface finish of the result.

The Z-axis resolution is dictated by the layer height at which the material is printed. The lower the Z-layer height is, the more layers there are in the entire print, and therefore you get more detail and accuracy. The higher the layer height, the less layers that are needed to complete the print, and therefore the print is quicker and "less accurate." The quotation marks on "less accurate" should not be mistaken to mean "incorrect," however. Most applications are often printed in either 100-µm layer height or 50-µm layer height. Though users are often told that 50 µm offers significantly more detail and accuracy, it does not make a huge difference for most resins and applications. The difference between printing at 100 µm and 50 µm is about half the size of a human hair. For certain applications like castable resins, restorations (crown and bridge), etc, it is typically important to maintain optimal accuracy, but for most applications, it is sufficiently accurate to print at 100 µm. However, keep in mind that these recommendations are a starting point, and the laboratory must make sure that the selected material and printer are validated to deliver the intended results.

Recommended Layer Heights:

• Splints/Night Guards: 100 µm

• Dentures/Try-ins: 50 µm to 100 µm

• Surgical Guides: 50 µm

• Crown and Bridge/Removables: 50 µm

• Impression Trays: 100 µm to 150 µm

• Aligner Models: 100 µm

• Indirect Bonding Trays: 100 µm

• Castable Resins: 50 µm

• Gingiva Masks: 50 µm to 100 µm

Material Choice and Manufacturer Validations

The number of 3D printing materials on the market has exploded and may seem overwhelming when initially entering the dental 3D printing space. The type of printer—open or closed source—and the type of job will help narrow down the available materials to the best choices. The material chosen for the job will in turn drive the choice of curing unit down the road, as different types of curing units may be more effective for certain materials. Material validations from the resin's manufacturer provide essential information regarding the printing method, the material settings, and the post-curing and post-processing method combination that will achieve the intended material performance properties. All of this information can be found in the resin manufacturer's Instructions for Use (IFU).

Washing Units

Different OEM companies have created washing units to help decrease labor time and increase throughput and efficiency. Regardless of the protocol or washing unit used, the author has identified two major requirements that should be met. First, the overall isopropyl alcohol (IPA) exposure should not exceed 5 minutes total. This specifically refers to the time that the 3D printed part spends fully submerged in IPA. Some OEM washing units apply different techniques to remove resin without directly submerging the part. Second, all residual resin must be fully removed from small, detailed areas (implant holes, intaglio surfaces, interproximal areas, etc). Even if not fully achieved using the washing unit, it is recommended to use a brush to ensure the part is fully cleaned.

Curing Units

There is a wide range of curing units on the dental market. Technologies range from flash bulb to broad-spectrum UV, LED, and more. Some curing units have advantages such as heating, vacuuming, and nitrogen hookup capabilities. Some have digital capabilities which allow the user to download and save resin profiles, while some do not. The author has had the pleasure of working with most of the available curing units on the market to determine which is best for users depending on the job to be done. Major factors to consider include cost, curing chamber size, and overall performance when curing. The most important factor out of the three is overall performance, especially with biocompatible resins.

LEDs have become the most popular technology for post-curing because they are inexpensive and widely available. When working with LED curing units, the wavelength plays a huge role in proper post-curing, especially for biocompatible resins. Curing occurs when the printed part is hit by sufficient light energy of an appropriate wavelength to create chemical bonds. These wavelengths can typically range from 365 nm to 405 nm.

Curing time varies depending upon the unit. Less powerful curing units can take 60 to 80-plus minutes to properly cure a print, while some of the more sophisticated units can cure in under 10 minutes. This has to do with the curing chamber design, proper UV light and light location, optimal LED wavelength, light reflection within the chamber, heat, etc.

Be sure to use a recommended curing unit and post-curing time, especially with biocompatible resins. Curing with a fully validated curing unit guarantees mechanical efficacy and safety to the user. Factors such as raw resin color, opacity, and viscosity must be taken into account. Proper curing can also be influenced by curing light resolution at the platform level and the Z-axis resolution of the printed part. For example, a print with a thicker layer height may not cure properly without an appropriately powerful projector in the curing unit.

An improper cure to any biocompatible resin can result in a non-compliant product, which increases the risk that patients will experience an unpleasant taste from the end device due to higher levels of extracted monomer. Improper curing can also create unwarranted fractures, splits, or breaks. The brittleness of a material is ultimately controlled by material composition and post-curing conditions. Most models, hard splints, guides, and castable resins can become brittle if over-exposed during post-curing.

Making a Decision

There are many factors to consider when purchasing a 3D printer. The author has helped dozens of dental professionals determine which workflow and equipment suit them best based on the needs of their practice or laboratory.

First, consider your laboratory's demand and the jobs for which 3D printing will be used. Do you plan to print splints, models, crowns, dentures, surgical guides, etc? What volume do you expect to print based upon your current work inflow—and do you forecast an increased volume in the future? Based upon the volume of work you expect and the price tag of the 3D printer, will it provide a positive return on investment?

Once you have narrowed down your choices based upon the above analysis, decide whether you would like an open-source printer, or whether you are satisfied with a closed system. Materials are defining the present and future of 3D printing, and the author recommends a printer that allows the laboratory to make use of any new materials that come on the market. Also look at any associated washing and curing units. Does the printer company offer their own curing unit? Are other curing units compatible with the printer?

The final step is to analyze the customer and technical support of the manufacturer or distributor of your top choices. Will you receive reliable support in the event of problems or failures? Will they offer training or education as you learn to use your new 3D printer?

After answering these questions, you should have, if not a final selection, then at least a short list of 3D printers which will suit your laboratory's needs.

About the Author

Benjamin Taylor
3D Printing and Product Development Engineer
Keystone Industries

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