A Glimpse into the Future

Long anticipated to reveal restorative solutions for dentistry, 3D printing of ceramics is a fairly new technology currently utilized in both the automotive and aerospace manufacturing sectors to create parts that can adequately absorb heat, benefit from a high degree of hardness, and have corrosive stability. All forms of ceramics from alumina and silica to zirconia can be printed with varying technologies and processes to produce a finished custom part in color. Two recently exhibited technologies that are capable of achieving this are lithography-based ceramic manufacturing (LCM) and nano-particle jetting (NPJ). The LCM technology allows the fabrication of 3D-printed ceramic parts with the same material properties as conventionally formed 3D parts. This is accomplished by embedding ceramic particles in resin, which facilitates the additive manufacturing or building of the materials. The resin is printed using the normal workflow processes deployed currently in the market and then processed in an oven for a long period of time with a slow temperature climb to eliminate the resin, leaving only the glass ceramic behind. The purged glass ceramic is then subjected to a sintering process to solidify the glass particles into a complete and cohesive product. Two companies capable of printing glass ceramic are LITHOZ (lithoz.com/en) and 3DCeram (3dceram.com), which, although neither have dental verticals, claim that this technology can be utilized in the fabrication of dental ceramic restorations. 3DCeram has developed a number of these technologies, processes, materials, and workflows, but they are not yet ready for the dental technology market. A representative from 3DCeram stated that, “Although the technology is available, it is not yet cost and time-effective for dentistry, since removing the resin requires a very slow burn out and ceramics do not like fast temperature fluctuations. This technology requires a significantly longer processing time than the milling technology used today.”

One additive technology manufacturer has already announced its intention to revolutionize the dental industry with its nano-particle jetting printing technology. XJet 3D (xjet3d.com), whose founder also began Objet 3D printers, offers very exciting technology, processes, and materials for 3D printing ceramics. XJet 3D says its XJet3D Printer will be available in late 2017 for jetting “liquid ceramics” and “liquid metal” with their NPJ technology. The material is the key. XJet has developed a way to take any glass or metal and process it into very fine nano-particles that are smaller than a micron. This nano-particle material then behaves as a liquid that can be jetted. The printer will have a heating element within that heats the chamber to 550°C and evaporates any remaining liquid, leaving a printed glass product. Because this technology provides fabrication processes using such small nano-particles, there is no post-processing needed and the resolution of the final product is very high. Avi Cohen, Head of Market Development for XJet, asserted that, “The technology is not limited in any way and can eventually do multi-layers with multi-colors. This ‘freedom of design’ will yield significant micro-layer thicknesses that are smooth and have very high resolution.” He went on to say that 3D printing is better than milling because there are no geometric restrictions or angulations to manufacture the part, lending the technology ideal for complex geometric cases and detailed anatomy. The printer to be offered by XJet3D will have a large build tray and be able to facilitate short runs with an output of 400 crowns in 4 to 5 hours.

Beyond the ability of jetting or 3D-printing ceramic restorations, there’s a tremendous benefit in the lack of post-processing that’s required with other modalities of manufacturing, both additive and subtractive. With XJet’s additive process and workflow uses single-step jetting with no plastics or resin binders, allowing the printed parts to go directly to sintering after printing. The support material is quickly and easily dissolved prior to the sintering process, leaving just the final object comprised of the desired final material (zirconia). This reduces fabrication time considerably. Furthermore, the printed zirconia crown is fully peaked, which means it is very isotropic and will only shrink approximately 15% during the sintering process. “We believe that this will redefine the way people work,” said Cohen. Currently, this material and processes is not FDA approved and therefore not available for the dental market, Cohen continued. Currently, the material and processes are not yet FDA-approved but are “in the process” with a third party to facilitate FDA approval.

Plastics and resins have been used in our profession for many years, but the ways in which we can now use a variety of materials for myriad indications offers the opportunity for very exciting and interesting innovations. DWS Systems (dwssystems.com) has introduced their “restoration-in-one-session” DFAB, a 3D printer designed to produce natural-looking teeth through its technology, materials, and software. The material is a biocompatible, non-toxic resin developed for 3D printing that produces an FDA-approved Class IIa restoration indicated for use as a long-term invasive medical device. The software that controls the process uses an innovative Photoshade system and offers the possibility for the dental laboratory to control color and shading as the restoration is printed. Currently, the validated shade gradation is in the range of A1 through A3.5, and the next update will offer shading in the B family of the Vita Classic shade guide. The technician can nest the precise location of the starting point and of the end point of the color to obtain the desired final shade. Furthermore, the representative declares that the material is extremely kind to the opposing dentition and wears more rapidly. The material’s current limitation is for a maximum of five connected teeth, which can be accomplished in as little as 20 minutes. The printer and material are expected to be available in fall 2017.

Another company offering a biocompatible FDA-approved Class IIa resin is NextDent (nextdent.com) by 3D Systems (3dsystems.com). Among their many resin offerings, the C&B MFH is a light-cured DLP solution for long-term restorations. The material is a micro-filled hybrid biocompatible resin said to offer a balance between inorganic fillers and resin. These properties can give printed restorations a high level of strength and wear resistance. “It is easy to finish, stain, and polish, and the degree of translucency allows for the restoration to blend well in the oral environment,” said Chuck Stapleton, 3D Systems Advanced Application Engineer-Dental. “You can print 20 crowns in 9 minutes.” Furthermore, NextDent uses a biocompatible FDA-approved Class IIa material for printing denture bases. The material exhibits very low shrinkage compared to standard poly-methyl methacrylate (PMMA) denture base materials. By using the base material along with the C&B MFH material and bonding them, the process delivers a finished digital denture solution.

3D Systems is launching a dental-specific 3D printer called Figure 4, which utilizes the DLP technology and is touted as printing with all NextDent light-cured materials in one printer. A dental laboratory could potentially use this to print trays, models, orthodontic models, surgical guides, orthodontic stents, crowns, and denture bases.

High-impact thermoplastics, also known as polyether-ether-ketone (PEEK) and polyether-ketone-ketone (PEKK), have been traditionally pressed or milled in the dental market. 3D printing/additive manufacturing offers geometric options for this material that may far outweigh those of milling or pressing and does not restrict the build of the object. Intamsys Technology Co. Ltd. (intamsys.com) introduced a less expensive 3D printer called FUNMAT HT, which is capable of printing with these high-impact polymers. This functional material printer deploys fused deposition modeling (FDM) technology that builds using heat—maintaining a build plate temperature of 160°C and an extruder temperature of 400°C. The temperature is constantly and evenly distributed by a heating bulb housed on the side of the printer. The high-impact thermoplastics can be layered 0.05 mm to 0.3 mm and have the potential to build any object from an STL file. Currently, the company does not have a presence in the dental market, but is actively working toward 510(k) compliance, at which point they will enter the dental/medical arena.

As more companies comply with US regulations, more materials and solutions will be made available for our profession. Currently, the larger stakeholders in additive manufacturing are submitting patents, ISO certification, and FDA compliance forms so they can best position their companies as the market segment grows exponentially. The FDA continues to clear 3D-printed medical devices with 87 medical devices granted approval since 2005. Certainly, additive manufacturing will grow and perhaps become the primary way we manufacture restorations in the future.

As the efficacy and development of additive manufacturing continues to grow at a robust 400% compounded revenue growth over the past 3+ years, many manufacturers are working on developing more automated processes that are scalable and continuous. Stratasys (stratasys.com) has launched their scalable Fortus Demonstrator Printers. These 3D printers are sold in three-printer columns and can be scaled up in groups of three. The technology offers the ability to continuously print multiple parts that use different materials and geometry. Once the printer is done with the throughput, it simply places the object in a bin and continues to print the queued file. This technology could expand production and produce many of the same parts at the same time or produce different parts simultaneously. Although this technology is not available yet, it is expected to come to market soon.

Continuous additive manufacturing is a priority for many stakeholders in the 3D printing industry. Among them is a company that holds many patents for the development of continuous technology called continuous digital light manufacturing (cDLM) and related materials in conjunction to additive manufacturing. In February 2017, EnvisionTEC launched its Vida cDLM 3D printer, which is the second printer using cDLM for high-speed printing. This 3D printer can print five partial frameworks in 2 to 2.5 hours and can print 12 crowns in about 16 minutes using the E-Dent 400 material (FDA-approved for long-term temporaries). “Continuous digital light manufacturing is the next evolution for additive manufacturing; it provides high-speed output, better accuracy, quicker post-processing, and significantly finer details,” said Chris Kabot, EnvisionTEC’s Dental Applications Specialist. These features that improve speed and accuracy as well as reduce post-processing time are key advancements. No longer does the printed part need to move up and down as it builds, meaning less support material is necessary. cDLM utilizes oxygen gas to strategically inhibit the curing of the resin in unwanted places and only where the design was intended, and therefore allows the building part to remain submerged in the liquid material and for the object to build significantly faster.

The prospect of new innovations, materials, and technology in additive manufacturing is very encouraging, specifically for dental technology and the way we conduct business, treat patients, and fabricate dental restorations. As companies large and small enter this space, we will continue to see novel manufacturing technologies and materials being implemented. We are now entrenched in the Fourth Industrial Revolution—in which 3D printing is a key player—and can now fabricate implant parts out of titanium or thermoplastics using additive manufacturing. We can produce customized zirconia orthodontic brackets and even make human body parts using “biosketching” technology, all using the same form of manufacturing.

Biosketching is a term used for 3D printing of a biologic object using live tissue cells or stem cells. This is a new and exciting segment, as there is much research in progress with a great deal of success. EnvisionTEC offers the BioPlotter 3D printer, which accomplishes a definitive fabrication of animal cells to produce a body part, like an organ, skin, etc. According to a recent study published by the Columbia University Dental School, researchers used this technology to print the cementum of a human tooth, which they implanted into a patient. The structure grew and was accepted into the body like its own.^2,3 Could we even be printing tooth replacements in the near future?

As we look ahead to what is possible, there is another innovative approach using similar technology called the REPLICATE System from Natural Dental Implants (NDI) (replicatetooth.com). Using CBCT scanning to digitize and replicate the failing natural tooth, a patient-specific, geometrically identical replicate tooth, complete with roots, is printed in titanium, allowing placement in the socket immediately after extraction. Another futuristic development in additive manufacturing is 4D printing. This technology offers a 2D-printed object that transforms to a 3D shape under different catalysts such as heat, moisture, etc. One can only imagine the possibilities and the potential awaiting our industry in the future. Keeping a close eye on the growing additive manufacturing market will give the dental laboratory professional an indication as to what technology laboratories may use in the future and how to best use such advances to meet their clients’ needs.

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